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TIMS ADVANCED MODULES and TIMS SPECIAL APPLICATIONS

1. DIGITAL CODE 2 INTEGRATE MESSAGE SELECTED AND HOLD MODE SELECTED MASTER BUFFER PHASE SIGNALS AMPLIFIERS SHIFTER STOLEN air 8 3kH2 TTL O Figure 1 TCM ENCODER MODULATOR BLOCK DIAGRAM Figure 2 TCM DECODER BLOCK DIAGRAM TIMS AIB TCM FRONT PANEL DECODER FACILITIES FUNCTIONS 3 position switch Inverts TCM symbol set to compensate for channel inversion BIO Input Code clock ADC Input Multilevel encoded sequence input TTL Output 1 Decoded data clock TTL Output 2 Decoded data FRONT PANEL INPUT OUTPUT ASSIGNMENTS TIMS AMS1 User Manual 71 USE 4 AM TCM MODULATOR MODULES REQUIRED CONVOLUTIONAL CODE ENCODER module with CODE 2 selected MULTIPLIER module MASTER SIGNALS module BUFFER AMPLIFIERS module SEQUENCE GENERATOR module or other digital data source e g PCM ENCODER module SETTING UP Before commencing with the TCM set up the user must be familiar with the setting up and operation of the CONVOLUTIONAL CODE ENCODER module Please refer to the Advanced Modules User Manual chapter describing the CONVOLUTIONAL CODE ENCODER module The modules required for the TIMS 4 AM TCM modulator are patched together as illustrated in Figure 1 on the previous page Next the amplitude of the 4 AM TCM symbols must be adjusted Using an oscilloscope observe the output of the MULTIPLIER module and
2. The analog message is presented to the 1 amp D1 input with the TTL level PWM clock presented to the CLK input The TTL level PWM signal is available at the 1 amp D1 output The negative or falling edge of the PWM output signal remains fixed with respect to the input PWM clock signal CLK it is the positive or rising edge that varies the pulse s width Note that the operation of the PWM function is directly affected by both the amplitude of the analog message and the frequency of the PWM clock Therefore these two parameters must be observed when setting up a PWM system i PWM Settings The default amplitude and PWM clock parameters required in order to achieve a PWM signal with a 10 to 90 pulse width range are given in the table below along with parameter limits PWM clock frequency Message amplitude Comments at CLK input at 1 amp D1 input 1kHz 2V to 2V Default parameters to achieve 10 to 90 PWM 500Hz lt CLK lt 10kHz 5V to 0 5V Typical maximum and minimum parameter settings When parameters other than the default settings are used it is recommended that the BUFFERS module is used to scale the message amplitude for required PWM operation ii Pulse Position Modulation Function The INTEGRATE amp DUMP and the TWIN PULSE GENERATOR modules may be used together to provide a pulse position modulation function To set up PPM first the INTEGRATE amp DUMP module must be set up for correct PWM operation Th
3. BIT CLOCK A TTL level clock must always be connected to the B CLK BIT CLOCK input The B CLK signal must be synchronised and aligned to the incomming encoded bit stream in the following manner each new bit transition of the incomming encoded data stream occurs on negative falling B CLK edges The STROBE output is derived from the incomming B CLK The positive going edge of the STROBE output is the exact moment the DECODER samples the incomming signal for the decoding process the decoded TTL output data is then immediately available at the DATA output TIMS AMS1 User Manual 30 RESETTING The DECODER module requires resetting after the B CLK or input waveform has been applied or interrupted Resetting of the LINE CODE ENCODER module is necessary as some Line Codes must be decoded from a known initial state for subsequent output data to be correct Two equivalent methods of resetting the ENCODER DECODER pair are available OPTION i requires a patching lead between the ENCODER DECODER pair while OPTION ii requires each module to be reset independently with no interconnecting patching lead i Automatic resetting of both modules Patch the DECODER S RESET output to the ENCODER S RESET input Momentarily depress either the ENCODER S or DECODER S RESET push button ii Manual resetting of each module Hold down the ENCODER S RESET push button while momentarily depressing the DECODER S RESET push b
4. El 4 D C m D z i lt Q o E VOLT METER BUFFERED DC INPUT OUTPUT BLOCK DIAGRAM FRONT PANEL USE The input signal may include AC and DC components If only the AC components of the signal are to be measured then select the AC coupling Otherwise select AC DC coupling Before connecting any input signals always select the 10V range first If greater resolution is required then select the lower ranges 2V or 200mV The DC OUTPUT provides a standard TIMS level buffered DC voltage which is directly proportional to the digital display s reading BASIC SPECIFICATIONS Input Ranges NOTE ACCURACY specified above applies to sinusoidal waveforms from 10 to 100 of full scale reading for the 200mV and 2V ranges and from 20 to 100 of full scale for the 10V range RANGE RESOLUTION MAX INPUT ACCURACY of reading of full scale AC AC DC DC 100Hz 10kKHZ lt 100kHz lt 500kHz 10V 10mV 10V 0 7 0 4 0 5 0 4 0 7 0 4 7 2 2V imV 10V 0 7 0 3 0 5 0 3 0 7 0 3 7 1 200mV 100uV 2V 0 7 0 3 0 5 0 3 0 7 0 3 7 1 Crest factor 8 1 peak voltage to RMS voltage NOTE The peak value must not exceed the MAX INPUT value specified above Maximum allowable input 15V peak all ranges Input impedance 100k ohm in parallel with less than 100pF Bandwidth DC 100Hz to 1 2MHz DC output approximately 1mV DC
5. TIMS ADVANCED MODULES and TIMS SPECIAL APPLICATIONS MODULES USER MANUAL Telecommunications Instructional Modelling System TIMS ADVANCED MODULES and TIMS SPECIAL APPLICATION MODULES USER MANUAL Issue Number 3 2 August 2001 All specifications are subject to change without notice Published by Emona Instruments Pty Ltd 86 Parramatta Road Camperdown NSW 2050 Sydney AUSTRALIA COPYRIGHT 1991 2001 by EMONA INSTRUMENTS PTY LTD TIMS is a registered trademark of AMBERLEY HOLDINGS PTY LTD Printed in Australia CONTENTS Part TIMS INTRODUCTION 1 TIMS OVERVIEW SYSTEM CONVENTIONS 2 Front Panel Sockets Plug in Modules Labelling Advanced Module Set Number 1 Module List 3 Part Il ADVANCED MODULES USER INSTRUCTIONS Baseband Channel Filters 4 Decision Maker 6 Delta Modulation Utilities 12 Delta Demodulation Utilities 18 Error Counting Utilities 22 Line Code amp Partial Response Encoder 25 Line Code amp Partial Response Decoder 30 Noise Generator 32 Wideband True RMS Volt Meter 33 100kHz Channel Filters 34 Spectrum Analyser Utilities 35 PCM Encoder 38 PCM Decoder 43 Block Code Encoder 46 Block Code Decoder 49 Convolutional Code Encoder 53 Convolutional Code Decoder 62 Integrate amp Dump 67 Trellis Code Modulation Decoder 71 Bit Clock Regeneration 78 FM Utilities 81 M Level Encoder 83 M Level Decoder 87 Digital Utilities 96 Quadrature Utilities 97 Speech Module 98 Multiple Sequences Source 100 CDMA Deco
6. offset for each input can now be measured and used in nulling any accumulated DC voltage offsets at the i amp q input terminals when viewing the Q amp I outputs Z MODULATION Three Z modulation modes are supported with variable level control Each mode is selected by positioning the Z MOD jumper Trimmer RV3 controls the level of the output signal MODE A position A normal intensity OV bright intensity 5V MODE B position B normal intensity 5V bright intensity OV MODE C position C normal intensity OV bright intensity 5V In each case trimmer RV3 will control the level of the bright intensity TIMS AMS1 User Manual 94 QUICK OPERATION GUIDE A Familiarisation with the decoding process 1 Patch together the following diagram with the M LEVEL DECODER module operating in STANDARD mode 2 Select the shortest sequence length for both SEQUENCE GENERATOR module 3 Trigger the oscilloscope on the SEQUENCE GENERATOR module s SYNC output 4 Experiment with the DECISION POINT control knob and the HUNT facilities DATA SEQUENCE M LEVEL BENERATOR ENCODER q wma i q MASTER SIGNALS 8 8kH2 TTL cLk MLEVEL DECODER DECISION POINT MoD DATA ERROR PULSE COUNTING COUNTER pan p ERROR TL iNpuT ux COUNTS Gk GATE ENABLE SEQUENCE GENERATOR RESET DATA LOCAL G
7. s EXTERNAL trigger input to the FS frame synchronisation signal Adjust the scope s timebase so that two or three frames of PCM data are visible For a more stable display of the individual PCM code words connect Vin to the TIMS VARIABLE DC module B TDM operation 1 Plug two PCM ENCODER modules into adjacent slots of the TIMS rack Select the front panel DIGITISING SCHEME switch to 4 bit LINEAR 2 Patch the TIMS MASTER SIGNALS module s 8 33kKHz SAMPLE CLOCK to both of the PCM ENCODER modules bit clock inputs CLK 3 Patch a lead from the TDM CONTROL MASTER output of one PCM ENCODER module to the TDM CONTROL SLAVE input of the other PCM ENCODER module The two modules now become MASTER and SLAVE respectively 4 Patch the MASTER PCM ENCODER module s MESSAGE output only to its Vin input Connect the SLAVE module s Vin input to the TIMS VARIABLE DC module s output 5 Observe each module s PCM DATA output signal separately and confirm the signals are as expected 6 Patch together the PCM DATA outputs of each PCM ENCODER module 7 Connect the oscilloscope s EXTERNAL trigger input to the FS frame synchronisation output of the MASTER PCM ENCODER module 8 Connect the oscilloscope s CH1 to the MASTER module s FS frame synchronisation output and CH2 to the common PCM DATA output 9 Adjust the oscilloscope s timebase so that two or three frames of PCM data are visible Visually determine which frame is M
8. DUMP module s DELAY control knob for a single ramp within the bit clock cycle 6 This completes the setting up of the TCM demodulator C Channel Simulation amp Bit Error Rate Measurement Options 1 Different transmission channels may be simulated using the 100kKHz CHANNEL FILTERS module 2 Noise may be added to the channel using the ADDER and NOISE GENERATOR modules 3 Bit Error Rate and Signal to Noise measurements can be made on the noisy channel in the same manner as with other TIMS digital modulation experiments using the ERROR COUNTING UTILITIES TRMS VOLT METER and associated modules TIMS AMS1 User Manual 77 BIT CLOCK REGENERATION Four independent functional blocks are provided which may be used independently or in combination with other TIMS modules to recover the bit clock of any TIMS generated Line Code Schemes which may be constructed and demonstrated using the building block functions of the BIT CLOCK REGENERATION module along with other TIMS modules include Bandpass Filter jitter reduction techniques Bandpass Filter bit sync derivation and Phase Lock Loop bit sync derivation using filter square law transition detector based and various other clock recovery structures DIVIDER BIT CLOCK OUTPUT REGEN DIVIDE BY N DIGITAL DIVIDER INPUT OUTPUT TRANSITION TRANSITION DIGITAL DETECTOR PULSE DETECTOR INPUT OUTPUT PULSE OUTPUT LOOP FILTER ANALOG FILTER FIXED PULSE I
9. are another twelve EXTENDED and sixteen EXPANDED counting modes Please refer to the SETTING UP section later in this chapter for more details SPECIAL NOTE When the Monostable s GATE output is connected to the TIMS PULSE COUNTER one count will always be registered at the instant the Monostable is TRIGgered and becomes active This is provided as a confirmation that the system is active Therefore this first count must always be deducted from the final count BASIC SPECIFICATIONS EXCLUSIVE OR GATE Inputs A amp B TTL level Output continuous X OR result or gated with HI time of the input CLK CLOCK input TTL level fmax gt 40kHz MONOSTABLE GATE active level DIP switch selectable active HI or active LO GATE time normal mode 10 10 10 10 extended mode normal mode x2 x4 or x8 expanded mode same as normal or extended modes BUT divides the PULSE COUNT selected by twelve GATE output LED continuously lit while GATE is active flashing only during last 10 of active time CLOCK input TTL level fmax gt 20kHz TRIG input depress push button or input signal TRIG signal level TTL level DIP switch selectable active level active HI or active LO TRIG signal min width gt 0 2uS TIMS AMS1 User Manual 23 SETTING UP THE MONOSTABLE TRIGGER INPUT LEVEL The TRIGger input level can be selected at switch SW1 The default position is HI when using the front panel push button switch for triggering the Monostable Note that the
10. bipolar RESET INPUT O 2 O IGITAL ENCODE unipolar DATA RESET BIP RZ 3 level RZAMI 3 level M CLK BOL bipolar TTL DATA cove O 3 level PATA Quosin C 3 level OUTPUT B CLK TTL MASTER O BIT cLock BLOCK DIAGRAM CLOCK INPUT OKA FRONT PANEL USE MASTER amp BIT CLOCKS A TTL level clock should always be connected to the M CLK MASTER CLOCK input Note that the frequency of the output B CLK signal will be one quarter of the applied M CLK signal A convenient M CLK source is the 8 3kHz TTL available from the MASTER SIGNALS module The input DATA stream should always be generated by or clocked with this module s B CLK BIT CLOCK signal Alignment between the incomming data and the B CLK must be such that each new bit TIMS AMS1 User Manual 25 transition of the TTL data stream occurs on positive going B CLK edges The resulting encoded bit appears at the ENCODER S outputs on the following negative B CLK edge If the PSEUDORANDOM SEQUENCE GENERATOR module is used to provide the DATA then clock the SEQUENCE GENERATOR using the ENCODER module s B CLK output directly RESETTING Press the RESET push button once the M CLK has been connected If during the course of the experiment the M CLK is interrupted then repeat the reset procedure by depressing the RESET push button Resetting of the LINE CODE ENCODER module is necessary as some Line Codes must commence from a known initial
11. sequences of up to 214 1 bits which is identical to the sequence generators provided on the MULTIPLE SEQUENCES SOURCE module iii a Zero crossing detector level translator iv two independent lowpass filters a data stream LPF and a carrier LPF CDMA DECODER CLOCK INPUT CLK CLK OUT DIGITAL DELAY CONTROL RESET FRONT PANEL USE DIGITAL DELAY DELAYED CLOCK CLK CLK OUT DELAY RESET PN SYNC n m OUT IN Eoy OUT o eas IN ee OUT BLOCK DIAGRAM The DIGITAL DELAY functional block allows the user to manually delay a series of clock pulses from 1uS to 1ms over two ranges The delay within each range is continuously variable and is adjusted via the front panel DELAY control The delay range is set via the PCB mounted DIP switches at SW2 See the table below for setting and timing details SW2 DATA mode SW2 CHIP mode Switch setting both switches ON both switches OFF Pulse width approx 14uS approx 1uS Delay 100uS to 1 000uS 1uS to 10uS TIMS AMS1 User Manual 103 The signal at CLK OUT is a series of narrow positive going pulses which have been delayed with respect to the positive edge of the CLK input signal The DIGITAL DELAY may be used when it is necessary to manually align a stolen or locally regenerated DATA or CHIP clock at the receiver PSEUDO NOISE SEQUENCE GENERATOR The CDMA DECODER module s seq
12. single bit error correct with Cx bit error detect BLKd2 x Even Parity Hamming 7 4 Odd Parity single bit error detect single bit error correct single bit error detect BLKd3 x Even Parity Hamming 7 4 Cyclic single bit error detect single bit error correct Set Up is provided as a special mode to allow setting up experiments more easily The PCM DATA frame is passed straight through the BLOCK CODE ENCODER module from PCM DATA input to BLOCK CODE output without alteration Error detection at the BLOCK CODE DECODER module takes the form of simply testing that the input frame s three zero bit locations bits 5 to 7 are zero if a non zero is detected then the ERROR DETECTED output will output a pulse for each frame in error ERROR INDICATION The BLOCK CODE DECODER module will provide a visual indication of occurrences of error detection and or error correction As well TTL level signal outputs are provided to allow electronic counting of detection correction events The signal at each ERROR INDICATION output is a bit wide pulse which will be output once per each frame in error Only one of the two ERROR INDICATION outputs is active for each Block Code selected The ERROR DETECT LED and output is only active for codes that can detect and not correct errors When a error is detected the DETECT LED will flash and a single pulse will occur at the DETECT output For example the Parity Check Codes will on
13. 1 Select CONVOLUTIONAL ENCODER module s front panel mode switch to NORMAL amp the front panel code switch to CODE 1 2 Plug the CONVOLUTIONAL ENCODER module into the TIMS rack 3 Choose either the SEQUENCE GENERATOR module or PCM ENCODER module as the digital data source for the CONVOLUTIONAL ENCODER module and plug it into the TIMS rack beside the CONVOLUTIONAL ENCODER module 4 Patch the TIMS MASTER SIGNALS module s 8 33kKHz SAMPLE CLOCK to the CONVOLUTIONAL ENCODER module s M CLK input 5 Patch the CONVOLUTIONAL ENCODER module s S CLK output to the SEQUENCE GENERATOR or PCM ENCODER module s clock input 6 Depress the CONVOLUTIONAL ENCODER module s mode switch momentarily to RESET and then return the switch to the NORMAL position 7 Patch the scope s CH1 to the encoder module s DATA output and the scope s CH2 to the bit clock output B CLK Observe the relationship between the bit clock and the encoded output data 6 Familiarise yourself with the encoder module s inputs and outputs and compare with the timing diagrams given in this TECHNICAL DETAILS section of this chapter 7 Select CODE 2 and repeat the above steps 5 to 6 TIMS AMS1 User Manual 60 REFERENCES 1 B Sklar Digital Communications Fundamentals and Applications 1988 Prentice Hall 2 R E Ziemer amp R L Peterson Introduction to Digital Communication 1992 Macmillan Inc 3 Y Jain Convolutional codes improve bit
14. 4 point 4 QAM 8 point 8 PSK Ea 8 point 8 QAM 16 point 16 PSK 16 point 16 QAM TIMS AMS1 User Manual 88 DATA OUTPUT A TTL level data stream of decoded data is output continuously at the DATA output The data stream is in phase and synchronised with the bit clock signal at the CLK input OUTPUTS Q amp amp OFFSET ADJUSTMENT The signals at the Q amp I outputs are the actual sampled and held representations of the q amp i input signals presented to the internal decoder s analog to digital converter Any accumulated DC offset in either the q or i branch may be viewed at the Q amp I outputs and nulled by adjusting the respective PCB mounted trimmer RV2 or RV1 Calibration of the PCB mounted trimmers RV1 and RV2 is given in the TECHNICAL DETAILS section later in this chapter Note that the Q amp I signals are offset by approximately 2 5V with respect to the q amp i input signals DECISION POINT CONTROL STANDARD MODE The decision point is the point at which the incoming signals q amp i are sampled within each q amp i signal s symbol At the sampling instant the internal decoder makes a decision as to the state or level of the sample Both inputs q amp i are sampled simultaneously The thresholds or decision boundaries which the internal decoder follows vary depending upon the constellation selected The six preset decision boundaries are illu
15. Companding Formats TIMS 4 bit A4 Law amp TIMS 4 bit U4 Law PCB selectable Frame Synchronisation FS synchronisation signal coincident with frame s LSB and also as embedded 0 1 0 1 code in the LSB of each frame Sinuous Message Output bipolar standard TIMS level and always synchronised to bit clock Message Frequency PCB switch selectable as ratio of bit clock 1 32 1 64 1 128 1 256 TDM Mode two channel TDM system with MASTER SLAVE control of two PCM ENCODER modules TIMS AMS1 User Manual 40 TECHNICAL DETAILS 1 TIMING DIAGRAMS The following timing diagram describes PCM ENCODER operation INPUT Vin CLK PCM FS BIT 7 65 43 2107 65 43 2107 65 4 3 2 10 PCM ENCODER timing diagram TIMING DIAGRAM DESCRIPTIONS INPUT Vin is the input voltage applied at input Vin The waveform is shown as presented to the analog to digital converter by the PCM ENCODER module s internal sample and hold circuit CLK is the applied bit clock at input CLK PCM is the serial data signal at the PCM DATA output Note that each frame s LSB bit 0 is shown as carrying the embedded 0 1 0 1 frame synchronisation sequence FS is the frame synchronisation signal as provided at the FS output 2 TIMS PCM CODE WORD RANGES 7 bit LINE
16. INPUT FRONT PANEL USE INPUT SIGNALS Two TTL level digital signals are required for correct operation BLOCK DATA the encoded serial digital data and CLK a synchronised and in phase bit clock Both these signals must be clean squared digital signals Note that the TIMS DECISION MAKER module may be required to clean up digital signals that have undergone any kind of distortion BLOCK DATA The format of the serial data expected at the BLOCK DATA input is exactly as generated by the TIMS BLOCK CODE ENCODER module 8 bit frame length with 7 bit codeword and a frame synchronisation bit at bit O LSB TIMS AMS1 User Manual 49 PCM DATA OUTPUT The format of the serial data expected at the PCM DATA output is the TIMS standard 4 bit digitised scheme 8 bit frame length with 3 most significant bits zero 4 message bits bit 4 is the most significant data bit and bit O LSB is the embedded frame synchronisation bit Refer to PCM ENCODER module user instructions in this manual for further details CODE SELECTION Three codes are provided for decoding codewords generated by the BLOCK CODE ENCODER module Selection is made via a front panel toggle switch The actual codes available depend upon the EPROM version provided Refer to the following table for a listing of available codes EPROM CODE 1 CODE 2 CODE 3 VERSION BLKd1 x Even Parity Hamming 7 4 Set Up single bit error detect
17. Patch the SAMPLER S analog output to one of the MULTIPLIER S inputs Patch the SAMPLER S ADAPTIVE CONTROL output to the MULTIPLIER S other input 3 Patch the MULTIPLIER S output to the INTEGRATOR S input 4 Finally patch the INTEGRATOR S output to a lowpass filter say the TIMS TUNEABLE LPF This completes the Adaptive Delta Demodulator TIMS AMS1 User Manual 21 ERROR COUNTING UTILITIES Two independent functional blocks are provided which in conjunction with other TIMS modules can be used to carry out Bit Error Rate measurements The two blocks are an Exclusive OR gate for comparing two digital data streams and a precise monostable for gating a pulse counter ERROR COUNTING UTILITIES A X OR A X OR B oo AeB OUTPUT INPUTS CLK CLOCK INPUT GATE TIME SELECTOR a ff ACTIVE PUSH BUTTON PULSE COUNT GATE TRIG INPUT O active TRIG LED TRIG TTL TRIG INPUT MONOSTABLE BIT CLOCK GATE GATE INPUT cate OUTPUT CLK FRONT PANEL BLOCK DIAGRAM USE EXCLUSIVE OR LOGIC GATE The X OR logic gate accepts standard TTL input signals It operates in two modes normal and pulse output i In normal mode no clock signal should be connected to the logic gate s CLK input The output will be an uninterrupted result of the X OR gate ii In pulse mode a clock signal must be connected to the logic gate s CLK input The logic gate s result will only be passed to the output during the clock s HI period
18. TIMS DSP RB EPROM Operation both TIMS DSP HS amp TIMS DSP RB i Plug the EPROMs into the TIMS DSP module Note that two EPROMs are required for the TIMS DSP RB module the EPROM labeled HI located in U5 and the EPROM labeled LO located in U6 ii Ensure the MEMORY SELECT JUMPERS in the TIMS DSP RB module are set for EPROM RAM mode A1 A2 A3 amp A4 and Jumper J1 should be in position L iii Plug the DSP module into the TIMS rack RAM Operation TIMS DSP HS only i Ensure the MEMORY SELECT JUMPER is set for RAM mode ii Ensure that EPROMs is not installed iii Plug the DSP module into the TIMS rack iv Connect the DSP module s SERIAL LINK to your computer s serial port reserved for communications with the DSP module and down load the decoder program required Setting up the TIMS AIB used only with TIMS DSP RB module i Remove the jumper at J1 NOTE jumper J1 must NOT be connected ii Plug the AIB module into the TIMS rack immediately to the right of the DSP module The TIMS DSP modules are now ready for operation TIMS AMS1 User Manual 65 QUICK OPERATION GUIDE A Setting up the Convolutional Decoder with Automatic Branch Word Synchronisation 1 Set up the CONVOLUTIONAL ENCODER module and verify correct operation 2 Set up the DSP modules as described previously in this chapter 3 Pass a stolen clock from the encoder to the decoder by patching the CONVOLUTIONAL ENCODER module s B CLK output to
19. Therefore if the logic gate s result is HI logic 1 the output will appear as one pulse or as a sequence of pulses if the result is HI for more than one clock cycle Typically the clock is an in phase and synchronised bit clock associated with the data streams being compared by the logic gate MONOSTABLE Clock Input A digital clock signal must always be connected to the CLK input Typically this would be the bit clock associated with the digital data of the experiment being carried out TIMS AMS1 User Manual 22 Trigger Input The output GATE signal is activated or TRIGgered by either depressing the front panel push button switch or applying a digital level signal to the TRIG input The output LED labelled ACTIVE is lit continuously while the GATE is activate and only flashes during the last 10 of the GATE period The LED is not lit when the GATE is not active While the output GATE is active the Monostable may be reTRIGgered at any time by depressing the TRIG push button or applying a signal to the TRIG input When reTRIGgering occurs the GATE output immediately clears becomes inactive and is then reactivated for the new monostable period GATE Time The output GATE time is determined by a preselected count of input clock pulses The number of clock pulses counted is selected initially by the PULSE COUNT front panel rotary switch Under normal mode four GATE times are available 10 104 10 and 10 clock pulses There
20. constraint length v 3 The parity check polynomials and structure are given below BIT 1 KR gt SERIAL OUTPUT BIT 0 Figure 1 CODE 1 structure Parity check polynomials for each branch of CODE 1 are BIT 0 branch H D D 1 and BIT 1 branch H D D D 1 Note that this code structure and its analysis can often be found in digital communications text books and in technical journals to illustrate the operation of convolutional encoders See references 1 2 and 3 at the end of this chapter CODE 2 is a systematic convolutional code with rate R 1 2 and constraint length v 4 The parity check polynomials and structure are given below DATA INPUT BIT 1 R gt SERIAL OUTPUT BIT O Figure 2 CODE 2 structure Parity check polynomials for each branch of CODE 2 are BIT 0 branch H D D D 1 and BIT1 branch H D D TIMS AMS1 User Manual 54 The parity check polynomials for CODE 2 were designed and published as suitable for amplitude modulation applications in Trellis Coded Modulation by G Ungerboeck in two IEEE publications See references 4 and 5 IMPORTANT Different definitions of constraint length v can be found in the literature on convolutional coding 2 Please refer to the TECHNICAL DETAILS section of this chapter for definitions used in this chapter MODE SELECTION The operating mode is selected by a three position front panel switch NORMAL Mode Wh
21. error rate is detected after the setting up procedure is completed then this may be caused due to phase inversion in the transmission channel Change the switch to the MIDDLE position to compensate for the channel s phase inversion The following table illustrates the internal changes within the Viterbi decoder TIMS AIB module s Viterbi decoder s ref SWITCH POSITION symbol set upper S0 1 5V S1 0 5V S2 0 5V S3 1 5V middle or S0 1 5V S1 0 5V S2 0 5V S3 1 5V lower TIMS AMS1 User Manual 73 BASIC SPECIFICATIONS Soft decision Viterbi decoder Modules required TIMS DSP DB and TIMS AIB or TIMS DSP RB and TIMS AIB Firmware Software required EPROM pair or floppy disk with decoder program Decoder technique implemented a soft decision Viterbi decoding algorithm with an Information Bit Path History Length of 16 5 times the constraint length of the code used Code clock input typ 1kHz TTL level synchronised and in phase with the encoded sequence Code sequence input 4 level convolutionally encoded sequence Data output decoded TTL level data sequence Clock Output typ 1kHz TTL level synchronised and in phase with the data sequence Input sequence inversion compensation manual via front panel switch TIMS AMS1 User Manual 74 SETTING UP THE DSP MODULES Please refer to the DSP User Manual for detailed setting up and user information The following is intended only as a quick reference g
22. input CLK accepts a TTL level signal It must be synchronised with the incoming i signal and its frequency must be the bit clock rate of the data CLOCK INPUT RANGE SETTING In order to optimize performance of the user variable decision point a PCB mounted RANGE jumper must be set to correctly match the input clock frequency Set the RANGE jumper to LO for clock frequencies up to 4kHz For clock frequencies above 4kHz set the RANGE jumper to HI CONSTELLATION SELECT BPSK MODE Two front panel CONSTELLATION SELECT switches are not used in BPSK mode DATA OUTPUT A TTL level data stream of decoded data is output continuously at the DATA output The data stream is in phase and synchronised with the bit clock signal at the CLK input OUTPUTS Q amp amp OFFSET ADJUSTMENT The signal at the I output is the actual sampled and held representation of the i input signal presented to the internal decoder s analog to digital converter Any accumulated DC offset in the i signal may be viewed at the I output and nulled by adjusting the respective PCB mounted trimmer RV1 Calibration of the PCB mounted trimmer RV1 is given in the TECHNICAL DETAILS section later in this chapter Note that the I signal is offset by approximately 2 5V with respect to the i input signal DECISION POINT CONTROL BPSK MODE The decision point is the point at which the incoming signal i is sampled at some point within the i signal s symbol At the sampling in
23. per digit giving 2V full scale TIMS AMS1 User Manual 33 100kHz CHANNEL FILTERS Three switch selectable 100kHz channels are provided comprising two different filters and one straight through connection 100kHz CHANNEL FILTERS CHANNEL SELECT SWITCH IN CHANNEL OUT CHANNEL SELECT INPUT COUPLING vi SWITCH AC ANALOG INPUT O OUTPUT IN OUT BLOCK DIAGRAM FRONT PANEL USE Only one channel may be selected and used at a time Note that each of the three channels may be AC or DC coupled by front panel toggle switch CHANNEL CHARACTERISTICS Before using any of these three channels in experiments each channel should be characterised by actual measurement of amplitude and phase responses As a minimum the cut off and stop band frequencies should be measured using the VCO and TRUE RMS METER modules or an oscilloscope BASIC SPECIFICATIONS Input coupling AC or DC channels 1 to 3 Channel responses Channel 1 straight through Channel 2 bandpass filter Channel 3 lowpass filter Stop band attenuation approx 40dB TIMS AMS1 User Manual 34 SPECTRUM ANALYSER UTILITIES A general purpose analog display module which will indicate positive and negative voltages in the frequency range DC to about 10Hz These characteristics make the module an ideal display device when learning about signal filtering signal mixing and traditional spectrum analyser concepts SPECTRUM UTILITIES RES
24. plugged in or removed at any time without turning off the system power The modules are not locked into position and may need to be held while interconnecting leads are removed C LABELLING All modules are identified as to the function they perform Inputs outputs controls and switches are labelled so that a student who has had only a brief introduction to TIMS can use the modules without needlessly referring back to this USER MANUAL It should be noted that no variable controls have calibration marks This is intentional as the philosophy behind TIMS is that students setup and adjust systems by observing and measuring signals This assists the student in gaining a much greater understanding feel and insight into the operation of a communications implementation TIMS AMS1 User Manual 2 D ADVANCED MODULES LIST Below are listed all the TIMS ADVANCED MODULES Baseband Channel Filters Decision Maker Delta Modulation Utilities Delta Demodulation Utilities Error Counting Utilities Line Code amp Partial Response Encoder Line Code amp Partial Response Decoder Noise Generator True RMS Volt Meter 100kHz Passband Channel Filter Spectrum Analyser Utilities PCM Encoder PCM Decoder Block Code Encoder Block Code Decoder Convolutional Code Encoder Convolutional Code Decoder Integrate amp Dump Trellis Code Modulation Decoder Bit Clock Regeneration FM Utilities M Level Encoder M Level Decoder Digital Utilities Q
25. record speech or other sounds on either channel set the front panel switch to RECORD and speak clearly into the microphone The length of your message may be from a few seconds up to 32 seconds As soon as you have finished your message set the switch to the PLAY position The recorded content will automatically repeat upon switching to PLAY Note that the length of the recorded message will only be the length of time the switch was in the RECORD position The recorded message is stored in non volatile analog storage arrays and is band limited from 300HZz to 3 4kHz Each channel has an independent Automatic Gain Control AGC that allows for a wide dynamic range of recorded sounds from very quiet to loud voice NOTE pcb mounted switch SW1 can be set to RECORD DISABLE to disable the front panel RECORD switch of either or both channels TIMS AMS1 User Manual 98 LIVE CHANNEL A third non recordable channel is also provided where the sound at the MICrophone is continuously output as an electrical signal The LIVE channel provides four filtering options with the two front panel selectable filters a 3 6kHz LPF and a 300Hz HPF INPUTS Two input sources are provided the MICrophone input and the EXTernal input The MiCrophone is a sensitive electret type microphone which is fixed in the front panel This one microphone is common to all three channels There is also a standard TIMS yellow input socket that allows electrical signals from oth
26. state for subsequent output signals to be correctly encoded and later decoded NEVER CONNECT together the SEQUENCE GENERATOR S RESET input with the ENCODER S RESET input This will have no effect SIGNAL LEVELS The Line Code waveforms have standard TIMS amplitude of 2Vp p Voltage levels used are Unipolar OV 2V Bipolar 2V 2V 3 level 2V OV 2V BASIC SPECIFICATIONS Inputs DATA TTL level digital signal M CLK TTL level digital signal fmax gt 400kHz Outputs B CLK TTL level digital signal LINE CODE outputs 2Vp p 10 TIMS AMS1 User Manual 26 DEFINITIONS OF ENCODED WAVEFORM FORMATS The encoded waveforms are described in the following manner Line Code s name description and lt output level gt input data state resulting output Line Code waveform input data state resulting output Line Code waveform NRZ L Non return to zero level lt bipolar gt 1 high level 0 low level NRZ M_ Nonreturn to zero mark lt bipolar gt 1 transition at beginning of interval 0 no transition UNI RZ_ Unipolar return to zero lt unipolar gt 1 pulse in the first half of the bit width O no pulse BIP RZ_ Bipolar return to zero lt 3 level gt 1 positive pulse in the first half of the bit width O negative pulse in the first half of the bit width RZ AMI Return to zero alternate mark invert lt 3 level gt 1 pulse in the first half of the bit width alternating pola
27. the 2kHz bit clock from the LINE CODE ENCODER module and patch it to the CONVOLUTIONAL CODE ENCODER module s CLK SYNC input iii RESET the LINE CODE ENCODER module iv RESET the CONVOLUTIONAL CODE ENCODER module TIMS AMS1 User Manual 56 The CONVOLUTIONAL ENCODER module through the use of CLK SYNC will synchronise its own clocking circuit to the bit clock presented at the CLK SYNC input The two module s bit clocks will now be synchronised and in phase Repeat the reset procedure whenever any clock signals are reset or disconnected BASIC SPECIFICATIONS Master Clock Input typically 8 33kHz approx 100KHz maximum TTL level Sample Clock Output must be used to clock the module providing the input data sequence Data Input serial TTL level Bit Clock Output synchronised and in phase with the serial encoded data Output Encoded Data serial and parallel TTL level and bipolar formats Serial Outputs TTL level and bipolar TIMS level Parallel Outputs TTL level and equispaced 4 level bipolar signal 1 5V to 1 5V Convolutional Encoders front panel switch selectable CODE 1 nonsystematic convolutional code with rate R 1 2 and constraint length v 3 CODE 2 systematic convolutional code with rate R 1 2 and constraint length v 4 Operating Modes font panel switch selectable NORMAL the input data sequence is mapped to the selected convolutional code and output TEST switches test sequence to encoder circuit input Test Sequence
28. the AIB module s BIO input 4 Patch the encoded sequence from the CONVOLUTIONAL ENCODER module to the AIB module s TTL Input 1 5 Select TEST CODE mode at the CONVOLUTIONAL ENCODER module 6 Select the upper switch position at the AIB module After the LED is lit return the switch to the middle position 7 Confirm that the decoded data at the AIB module s TTL Output 2 is a constant logical high Recall that the test code at the CONVOLUTIONAL ENCODER module is a constant logical high 8 Select the lower position at the AIB module s switch Observe at the AIB module s TTL Output 2 that the CONVOLUTIONAL ENCODER module s test code is no longer being correctly decoded 9 Return the AIB module s switch to the middle position for correct decoding 10 Change the CONVOLUTIONAL ENCODER module s mode switch to NORMAL 11 The convolutional encoder and decoder set are now ready for correct operation TIMS AMS1 User Manual 66 INTEGRATE amp DUMP Two independent functional blocks are provided The first block is a variable digital delay for TTL level clock signals and may be used for aligning the phase of a bit clock to a data stream The second block includes dual channel sampling integrate amp dump and holding functions which can be switched in three combinations Sample amp Hold Integrate amp Dump Integrate amp Hold A forth switch selectable function is only available on channel 1 P
29. the PCM DATA input is exactly as generated by the TIMS PCM ENCODER module TIMS PCM code words in standard offset binary with the first 7 bits allocated for data coding and the least significant bit allocated for the frame synchronisation code TIMS AMS1 User Manual 43 The three digitising schemes provided by the TIMS PCM ENCODER module can be decoded Selection is made via front panel switch a 7 bit linear b 4 bit linear and c 4 bit companded either TIMS A4 Law or TIMS 4 Law Note that selection between TIMS A4 Law or TIMS 4 Law is made via jumper selector on the PCM DECODER module s PCB ANALOG OUTPUT Vout provides a bipolar standard TIMS level analog signal derived from the input digital data at PCM DATA Note that Vout is taken directly from the converter without reconstruction filtering so that individual steps in the conversion process may be observed if desired FRAME SYNCHRONISATION Two methods are used to recover frame synchronisation EXTERNAL makes use of a separate TTL level input signal connected to EXTERNAL FS and EMBEDDED extracts the embedded code within the digitised serial data The method required is selected by front panel switch EXTERNAL or EMBEDDED i EXTERNAL Mode In EXTERNAL mode the separate frame synchronisation input signal EXTERNAL FS must normally be low and should only go high for one bit period at the time of the least significant bit of the PCM code word bit 0 Note tha
30. the user Using an oscilloscope the decision point is displayed as a bright marker on the input waveform The sampled and held signal is also output The BPSK decoding format is enabled via a special operating mode of the M LEVEL DECODER module M LEVEL DECODER not used OM 3 not used 16 DECISION POINT SLOW FLASHING DECISION POINT Bt TJ I not used Z MODULATION OUTPUT not used BPSK Z MOD not used not used l decoder DATA BPSK INPUT SAMPLED amp HELD CLK CLOCK DECODED BLOCK DIAGRAM INPUT DATA OUTPUT FRONT PANEL BPSK OPERATING MODE USE SPECIAL OPERATING MODE BPSK MODE To switch the M LEVEL DECODER module to the SPECIAL operating mode for decoding BPSK signals only then i remove the M LEVEL DECODER module from the TIMS rack ii press the HUNT push button and while keeping the HUNT push button depressed plug the module into the TIMS rack iii Confirm that the HUNT LED immediately starts and continues flashing slowly approximately one flash per second The slow regular flashing of the HUNT LED indicates that the M LEVEL DECODER module is operating in the SPECIAL mode INPUT SIGNALS BPSK MODE Two input signals are required for BPSK operation a bipolar signal i and the data clock CLK INPUTS q amp i The peak to peak amplitude of the i signal must be approximately 2 5V for optimum decoding performance The q input is not used TIMS AMS1 User Manual 91 CLOCK INPUT The clock
31. upon the selected code Frame Synchronisation Input FS synchronisation signal is taken from the preceding module typically the PCM ENCODER module Embedded Frame Synchronisation Signal is not altered by the encoding process Linear Block Codes dependent upon EPROM version installed Parity even Hamming single error correction Parity odd Cyclic TDM Mode compatible with data generated by two PCM ENCODER modules operating in TDM mode TIMS AMS1 User Manual 48 BLOCK CODE DECODER Frames of digital data which have been encoded using the BLOCK CODE ENCODER module are decoded with error detection and or correction depending upon the selected code Error detection and error correction indication amp output signals are provided as appropriate to the selected code Frame synchronisation may be achieved either from an external synchronisation signal or may be extracted from the embedded frame synchronisation code within the data received stream The bit clock provided must be synchronised and in phase with the incoming digital data Code selection is made via a front panel switch BLOCK CODE DECODER ERROR INDICATION ERROR ret O DETECTED corro Q O ERROR CODE PCM N K PARITY BLOCK CODE SELECT HAMMING CORRECTED WORD DATA FS SELECT i FRAME SYNC SELECT extF EMBED CLOCK EXTERNAL FS O s s O FS OUT BLOCK DIAGRAM SERIAL CODEWORD O O DECODED INPUT gtock pem PCM DATA DATA DATA BIT CLOCK
32. 11 symbol depending upon the constellation selected TIMS AMS1 User Manual 85 QUICK OPERATION GUIDE A DEMO Mode 1 Set PCB mounted jumper J3 to DEMO position 2 Connect a TTL clock to the CLK input For example use the 8 3kHz from the MASTER SIGNALS module 3 Select the constellation required via the front panel switches 4 View the Qbranch and ibranch Output signals on an oscilloscope in XY mode B NORMal Mode with SEQUENCE GENERATOR module 1 Set PCB mounted jumper J3 to NORM position 2 Plug the SEQUENCE GENERATOR and M LEVEL ENCODER modules into the TIMS rack 3 Connect a TTL clock to both modules CLK input For example use the 8 3kHz from the MASTER SIGNALS module 4 Patch the SEQUENCE GENERATOR module s TTL level X output to the M LEVEL ENCODER module s DATA input 5 Select the constellation required via the front panel switches 6 View the Qbranch and ibranch Output signals on an oscilloscope in XY mode C M QAM amp M PSK Generation 1 Follow steps 1 to 6 as described in section B above and then patch together two MULTIPLIER and an ADDER module as illustrated below SEQUENCE M LEVEL MULTIPLIER MULTIPLIER ADDER GENERATOR ENCODER DATA pata q L_ CLK LK M PSK ar M QAM MASTER SIGNALS 100kHz SINE 100kHz COS 8 3kHz TTL m QAM amp m PSK Generator Block Diagram TIMS AMS1 Us
33. 37 PCM ENCODER An audio frequency analog to digital converter which outputs the digitised data in serial TTL level PCM format Both linear and non linear logarithmic digitising schemes are provided Frame synchronisation is implemented by both separate output synchronisation signal and also an embedded code within the serial data stream A variable frequency sinuous type message is provided which is always synchronised to the input bit clock Two PCM ENCODER modules may be connected in parallel with the appropriate control signal to establish a two input channel single data line Time Division Multiplex system PCM ENCODER TDM CONTROL TDM SLAVE TDM MASTER INPUT OUTPUT SLAVE SYNCHRONISED ioe DIGITISING MESSAGE ANALOG PCM SCHEME e SELECT Aek LINEAS INPUT DATA 4 bit COMPAND FRAME SYNC O OUTPUT ANAL be SERAL Pem BIT Vin PCM DATA DATA CLOCK in BIT CLOCK INPUT CLK BLOCK DIAGRAM FRONT PANEL USE INPUT SIGNALS Two input signals are required for correct operation the analog signal to be digitised Vin and the sampling bit clock CLK Vin will accept TIMS level bipolar signals ranging from DC up to several kilohertz Note that the Vin input is not band limited so that aliasing may be observed if desired The bit clock CLK must be a TTL level signal such as the TIMS MASTER SIGNALS 8 33kHz SAMPLING CLOCK output Note that careful consideration must be give
34. AR Frame 0000000X 2 5V to 1111111X 2 5V 4 bit LINEAR Frame 0000000X 2 5V to 0001111X 2 5V 4 bit COMPANDED Frame 0000000X 2 5V to 0001111X 2 5V Notes i The Least Significant Bit X is the frame synchronisation bit ii In 4 bit schemes bit 5 becomes the data s Most Significant Bit 3 TIMS 4 bit A4 Law amp TIMS 4 bit U4 Law TIMS 4 bit Ag Law amp TIMS 4 bit U4 Law are included to demonstrate the increase in dynamic range obtained when using companding techniques Both TIMS companding laws are implemented with 4 bits rather than 8 bits and are intended to approximate the characteristics of the industry standard A 87 6 Law and p 255 Law respectively TIMS AMS1 User Manual 41 QUICK OPERATION GUIDE A Basic PCM ENCODER module operation using the synchronised sinuous MESSAGE 1 Select the PCB mount switch SW2 to read off off Also select the front panel DIGITISING SCHEME switch to 4 bit LINEAR 2 Plug the PCM ENCODER into the TIMS rack 3 Patch the TIMS MASTER SIGNALS module s 8 33kKHz SAMPLE CLOCK to the PCM ENCODER module s bit clock input CLK 4 Patch the PCM ENCODER module s MESSAGE output to the Vin input 5 Connect the oscilloscope s EXTERNAL trigger input to the MESSAGE output 6 Connect the scope s CH1 to the FS frame synchronisation output and CH2 to the PCM DATA output to view a most of or a full cycle of the MESSAGE signal 7 Next connect the oscilloscope
35. ASS FILTER as the source of a corrupted digital stream make an ideal demonstration 1 Select the appropriate digital waveform being used for the experiment at rotary switch SW1 which is located at the rear of the module 2 Select the correct Z modulation mode to suit your oscilloscope See TECHNICAL DETAILS section on setting up Z modulation 3 Select INT at DECISION switch SW2 near the front of the module 4 Connect the digital signal to IN1 and the bit clock to B CLK input 5 Connect the oscilloscope s EXTERNAL trigger input to B CLK input 6 Connect the oscilloscope s Z modulation input to Z MODULATION output of the DECISION MAKER module TIMS AMS1 User Manual 10 7 Connect the scope CH1 to IN1 and CH2 to OUT1 8 Select a timebase such that one or two EYE S are visible 9 Turn the DECISION POINT control and observe the movement of the bright marker along the input waveform TIMS AMS1 User Manual 11 DELTA MODULATION UTILITIES one bit differential pulse code modulation DPCM DELTA MODULATION UTILITIES SECTION GUIDE USER INFORMATION 12 SETTING UP 13 BASIC SPECIFICATIONS 14 INTEGRATOR OVERVIEW 15 QUICK OPERATION GUIDE 16 Three independent building blocks are provided which in conjunction with other TIMS modules can be used to make a simple Delta Modulator a Delta Sigma Average Modulator or an Adaptive Delta Modulator Both clock rate and step size can be varied in each of the
36. ASTER and which frame is SLAVE TIMS AMS1 User Manual 42 PCM DECODER An audio frequency digital to analog converter which accepts digital data in serial format as generated by the PCM ENCODER module Frame synchronisation may be achieved either from an external synchronisation signal or may be extracted from the embedded frame synchronisation code generated by the PCM ENCODER module The bit clock provided must be synchronised and in phase with the incoming digital data Two PCM DECODER modules may be connected in parallel with the appropriate control signal to decode the data generated by two PCM ENCODER modules operating in Time Division Multiplex mode PCM DECODER TDM CONTROL TDM TDM SLAVE INPUT MASTER SLAVE OUTPUT PCM ANALOG DIGITISING SCHEME SUNEN DATA OUT SELECT Ones FS SELECT BIT FRAME SYNC SELECT a2 coco ELOK EXTERNAL FS FS OUT BLOCK DIAGRAM O FS FS O SERIAL PCM DATA O ANALOG PCMDATA Vau OUTPUT BIT CLOCK INPUT O FRONT PANEL USE INPUT SIGNALS Two TTL level digital signals are required for correct operation PCM DATA the serial digital data to be converted to an analog signal and CLK a synchronised and in phase bit clock Both these signals must be clean squared digital signals Note that the TIMS DECISION MAKER module may be required to clean up digital signals that have undergone any kind of distortion PCM DATA The format of the serial data expected at
37. ATION SELECT switches are used to choose the encoding format required The upper 2 position switch selects between either a circular phase or square amplitude array The lower 3 position switch selects the number of points in the constellation 4 8 or 16 The following table lists switch settings required for generating the six available constellations Front Panel Switches Constellation Front Panel Switches Constellation Upper Lower Selected Upper Lower Selected 4 point 4 PSK 4 point 4 QAM D 8 point 8 PSK fA 8 point 8 QAM 16 point 16 PSK 16 point 16 QAM The Space Diagrams for the above constellations are shown below 4 PSK 8 PSK 16 PSK 4 QAM 8 QAM 16 QAM OUTPUT SIGNALS Two multi level analog signals are output labeled qbranch and ibranch The number of discrete M levels and the voltage difference between each level is determined by the front panel CONSTELLATION SELECT switch settings See the table below Front Panel Switches Number of Front Panel Switches Number of Upper Lower M levels ati amp q Upper Lower M levels ati amp q 4 point 3 4 point 2 O 8 point 4 E 8 point 4 16 point 8 16 point 4 For each of the six available settings the peak to peak amplitude of the ibranch and Qbranch signals will always be 2 5V TIMS AMS1 User Manual 84 BASIC SPECIFICATIONS DATA In
38. B mounted trimmer RV2 or RV1 Note that the Q amp I signals are offset by 2 5V AV where A V is 0 25V and can be varied at RV1 for input and RV2 for input Q Hence up to 0 25V of DC offset presented at either the i or q input may be nulled using RV1 or RV2 CALIBRATING RV1 amp RV2 FOR ZERO INPUT The following procedure will calibrate the input signals offset to the decoder s analog to digital converter for zero offset with both inputs grounded The procedure applies to both STANDARD and BPSK operating modes 1 Plug the M LEVEL DECODER module into the TIMS rack running in STANDARD mode 2 Switch to the 4 QAM constellation 3 Patch both the i amp q inputs to the TIMS GROUND connector at the VARIABLE DC module 4 Patch the 8 3kHz TTL signal at the MASTER SIGNALS module to the CLK input 5 Whilst viewing the DATA output on an oscilloscope slowly trim RV1 and RV2 until a stable TTL low logical 0 data just appears at the DATA output This procedure trims the i amp q input s A V offsets just inside the positive right hand quadrant of the 4 QAM space diagram Refer to the M LEVEL ENCODER module s signal state space diagram to confirm that in 4 QAM the data group 0 0 falls in the top right hand positive quadrant Hence as soon as stable 0 0 data appears at the decoder s DATA output both of the i amp q input signals have just fallen inside the positive right hand quadrant This reference
39. CODER module s output must be used and passed on to the required modules ii Embedded Frame Synchronisation The BLOCK CODE ENCODER module passes the embedded Frame Synchronisation information at bit 0 from input to output without alteration Refer to the PCM ENCODER module s user instructions in this manual for further details regarding frame synchronisation TDM MODE TDM data streams constructed by preceding PCM ENCODER modules connected in parallel refer to PCM ENCODER module user instructions in this manual are transparent to the operation of the BLOCK ENCODER module Only one BLOCK CODE ENCODER module is required to encode the TDM data The two PCM ENCODER modules must have a 4 bit digitising scheme selected to enable the BLOCK CODE ENCODER module to function correctly The same or different 4 bit digitising schemes may be selected simultaneously Note that all three modules must be supplied with the same bit clock CLK BASIC SPECIFICATIONS PCM Data Input serial TTL level PCM Data Input Format 8 bit frame with 3 most significant bits zero 4 message bits bit 4 is most significant data bit and bit 0 LSB is the embedded frame synchronisation bit Bit Clock Input typically 2kHz lt 8kKHz maximum TTL level Output Block Data serial TTL level Output Block Data Format 8 bit frame with 7 bit codeword plus LSB as embedded frame synchronisation bit 1 2 or 3 most significant bits allocated as check bits depending
40. DER S RESET push button Then release the ENCODER S RESET push button Repeat the RESET procedure whenever the ENCODER S M CLK signal the DECODER S B CLK signal or the input waveform to the DECODER is disconnected or interrupted 7 All the Line Codes are now generated and available simultaneously at the ENCODER S outputs Patch any one of the ENCODER S outputs to the corresponding DECODER input Note that some Line Codes require RESETTING prior to correct operation TIMS AMS1 User Manual 29 LINE CODE amp PARTIAL RESPONSE DECODER PCM WAVEFORMS amp DUOBINARY SIGNALING Each of the encoded signals generated by the LINE CODE ENCODER module can be decoded producing a TTL level data stream A synchronised bit clock with correct alignment must be provided to the DECODER LINE CODE DECODER RESET PUSH BUTTON NAZ L NAZ M RESET UNi n2 RESET OUTPUT ENCODED datos eater SIGNAL INPUTS RZ AMI BiD L OICODE TTL DATA OUOBIN PATA arcon OAE B CLK STROBE FRONT PANEL USE RESET LEVEL SHIFTER INPUT B CLK daa jaaa a IGITAL DECODE TTL DATA pee F STROBE BLOCK DIAGRAM The incomming encoded signal must be clean and distortion free The task of cleaning and squaring a recovered signal must be carried out beforehand by other modules such as the TIMS DECISION MAKER Only one encoded signal may be applied to any DECODER input at any one time
41. ENERATOR Basic Constellation Encoder amp Decoder with error counting B Familiarisation with modulated and demodulated constellation 1 Patch together the following diagram with the M LEVEL DECODER module operating in STANDARD mode Initially select 4 QAM 2 Select the shortest sequence length for both SEQUENCE GENERATOR modules 3 Trigger the oscilloscope on the modulator s SEQUENCE GENERATOR module s SYNC output 4 Experiment with and observe the effect of the PHASE SHIFTER module m QAM m PSK Modulator amp Demodulator with error counting SEQUENCE M LEVEL MULTIPLIER MULTIPLIER ADDER PHASE MULTIPLIER TUNEABLE MULTIPLIER TUNEABLE M LEVEL ERROR PULSE GENERATOR ENCODER SHIFTER LPF DECODER COUNTING COUNTER PS ERROR Tr put B DECISION 4 X POINT clk a x X XK x zmo COUNTS DATA pate Q Q i a ae ak ak ok o lo omel ENABLE f PHASE f SHIFTER i MASTER f SEQUENCE SIGNALS GENERATOR i 1O0DkH2 SINE 1 RESET 400kH2 cos STOLEN QUADRATURE CARRIER OQ 1 I I i aake TTL e H Lo Ja pata 1 I staren Lock t i MODULATOR i DEMODULATOR LOCAL GENERATOR TIMS AMS1 User Manual 95 DIGITAL UTILITIES Provides six independent digital dividers a digital inverter and a logical HI output DIGITAL UTILITIES LOGICAL HI INVERTER
42. ET FOR PEAK HOLD PEAK HOLD MODE ofa o CENTRE ZERO ANALOG PANEL METER NORMAL OPERATION INCREASED SENSITIVITY NORMAL SENSITIVITY ANALOG INPUT LPF OUTPUT IN OUT BLOCK DIAGRAM FRONT PANEL USE The analog center zero panel meter indicates the magnitude and polarity of the voltage applied at the IN socket The voltage at the IN socket is first filtered by a 30Hz lowpass filter before being scaled and applied to the panel meter A scaling facility allows the user to adjust the meter s full scale deflection over a wide input voltage range A PCB mounted trimmer RV1 is used for this scaling purpose When the PCB mounted trimmer RV1 is set FULLY CLOCK WISE then the panel meter will indicate FULL SCALE DEFLECTION with 2V DC input Turning RV1 ANTI CLOCK WISE will increase the meter s sensitivity that is FULL SCALE DEFLECTION will become less than 2V The front panel x1 x10 sensitivity switch provides a simple method of quickly increasing the full scale sensitivity of the meter by a factor of 10 times or 20dB A PEAK HOLD with push button RESET facility is available to assist in determining the peak value of a fluctuating reading The PEAK HOLD function reads only negative polarity peak voltages The signal at the OUT socket is equal in magnitude and opposite in polarity to the signal that is presented to the panel meter BACKGROUND The panel meter is a simple bipolar DC voltage meter TIMS A
43. HUNT push button This is intended as a facility for an adaptive or automatically synchronising system HUNT LED In STANDARD operating mode the HUNT LED is used to confirm that a hunt has been initiated by the pressing of the HUNT push button or the presentation of a valid signal at the HUNT input The HUNT LED is normally off until a hunt is initiated When the LED is on both the HUNT push button and input are inhibited till the LED goes off The HUNT LED will also turn on to indicate that the signal at the DATA output is invalid and a different region for sampling should be selected Note no decision is made by the decoder regarding the correctness or errors in the decoded data Z MODULATION OUTPUT The Z MODULATION output provides a pulse at the sampling instant These pulses may be viewed on the oscilloscope s screen or may be connected to the oscilloscope s Z modulation input To display the sampling instant connect the M LEVEL DECODER module s Z modulation signal at the front panel BNC connector to the oscilloscope s Z modulation input Refer to the TECHNICAL DETAILS section later in this chapter on setting up the Z modulation facility TIMS AMS1 User Manual 90 SPECIAL OPERATING MODE BPSK MODE A single baseband bipolar signal is sampled decoded and output as a continuous serial TTL level data stream The output data is synchronised and in phase with the bit clock The input signal is sampled at a point determined by
44. IONS DIVIDE BY N Input amp Output TTL level digital signals Clock input lt 1MHz Divisors 1 2 4 and 8 switch selectable TRANSITION DETECTOR Input amp Output TTL level digital signals Output Pulse Width with FIX selected at J12 approx 250us with VAR selected at J12 adjustable from approx 10us to approx 500us LOOP FILTER Input amp Output standard TIMS level analog signals Type conventional passive Type 1 second order loop structure refer to the previous page for definitions Characteristics required to be determined by the student See previous page for details Buffering active DUAL BANDPASS FILTERS Input amp Output standard TIMS level analog signals Number two identical bandpass filters Type fourth order Chebyshev with 3dB passband ripple Q approx 22 fixed Ratio of Tuning Clock to Filter s Centre Frequency 50 Internal Clock Frequency 104kHz crystal derived giving 2 083kHz filter centre frequency External Clock Frequency Range 50kHz to 250kHz TTL level TIMS BIT CLOCK REGEN User Manual 80 FM UTILITIES Three independent functional blocks are provided which are used in combination with other TIMS modules to make an 100kHz wideband FM modulator implementing the frequency multiplier method FM UTILITIES FM MASTER SIG 100kHz MASTER e SIGNAL INPUT ue MASTER AS 11 1kHz SINE 100kHz 111k OUTPU SIGNAL P OUTPUT INPUT CLIPPER 2 CLIPPER 2 CLIPPER 2 INPUT OUTPUT INP
45. L signal Change jumper J1 to position 12 The monostable will now internally divide by 12 the number of counts selected at PULSE COUNT the front panel rotary switch In this way both the input clock and number of selected counts are effectively divided by twelve and so producing the correct GATE time The front panel rotary switch PULSE COUNT and DIP switch SW2 are used to directly determine the GATE time as before but based on an 100kHz clock No additional calculations or divisions are necessary For example an experiment with a 100kHz bit clock and requiring a 10mS gate time Use the 8 333kHz TTL signal as the clock input Position jumper J1 to 12 Select 10 at the front panel PULSE COUNT rotary switch Select x1 at the COUNT MUTL switch SW2 This set up will count the EQUIVALENT of 1 000 pulses of a 100kHz signal giving a 10mS gate time TIMS AMS1 User Manual 24 LINE CODE amp PARTIAL RESPONSE ENCODER PCM WAVEFORMS amp DUOBINARY SIGNALING ENCODER SECTION GUIDE USER INFORMATION 25 BASIC SPECIFICATIONS 26 ENCODED WAVEFORM FORMATS USED 27 QUICK OPERATION GUIDE 29 A TTL level data stream is simultaneously encoded into eight Line Codes PCM Waveforms and one Precoded Duobinary Code The incomming data stream must be clocked by the ENCODER S bit clock output LINE CODE ENCODED ENCODER SIGNAL OUTPUTS RESET R z LEVEL SHIFTER RESET PUSH BUTTON biporer RESET NAZ M O
46. LTIPLIER module to the 1 amp D2 input Select integrate amp dump mode for 1 amp D2 at SW2 Vary the INTEGRATE amp DUMP module s DELAY control while observing the 1 amp D2 output Adjust the DELAY for a single ramp within the bit clock cycle ii Soft decision Viterbi decoder implementation signals The TIMS implementation of the TCM Viterbi decoder requires 2 input signals An in phase and aligned bit clock provided by the INTEGRATE amp DUMP module s READY signal This is presented to the TIMS AIB module s BIO input Multilevel encoded data provided by the INTEGRATE amp DUMP module s I amp D1 output This signal is presented to the TIMS AIB module s ADC input As this Viterbi decoder is performing its calculations based on soft decision coding an analog rather than TTL input is required The TIMS TCM Viterbi decoder provides two output signals The decoded data standard TTL level format at the TIMS AIB module s TTL Output 2 An in phase and aligned bit clock standard TTL level format at the TIMS AIB module s TTL Output 1 Channel phase inversion The TIMS TCM decoder also provides manual control over the decoder s internal reference symbol set via the TIMS AIB module s front panel 3 position switch This is necessary if the TCM signal undergoes phase inversion while passing through the transmission channel Initially the TIMS AIB module s front panel switch should be in the UPPER position If a large
47. M DATA coincident Output Signal 2Vpk DC coupled Frame Synchronisation LINE and EMBEDDED modes LINE Mode synchronisation signal coincident with frame s LSB EMBEDDED Mode search and extract 0 1 0 1 code in LSB of each frame EMBEDDED Mode Search 32 64 128 and 256 consecutive frame synch bits PCB switch TDM Mode two channel TDM system with MASTER SLAVE control of two PCM DECODER modules TIMS AMS1 User Manual 45 BLOCK CODE ENCODER Specifically formatted 8 bit frames of data are input and 8 bit codeword frames are output Check bits generated by the selected linear code are inserted into predetermined bit positions within the frame Note that this encoder will maintain a constant frame length of 8 bits by replacing up to 3 redundant data bits with check bits depending upon the selected linear code All three digital input signals must always be provided Code selection is made via a front panel switch BLOCK CODE ENCODER CODE SELECT BLOCK PARITY CODE HAMMING SELECT ia lie n k CODEWORD EXTERNAL FS SERIAL PCM DATA FS SERIAL FS IN PCM stock CODEWORD DATA DATA BIT BIT CLOCK CLOCK BLOCK DIAGRAM INPUT FRONT PANEL USE INPUT SIGNALS All three TTL level input signals must be provided for correct operation A TTL level bit CLOCK synchronised and in phase with the serial PCM format data A TTL level DATA stream pre formatted in frames of 8 bits Correctly pre fo
48. M THRESHOLDS OUTPUT CODE FORMAT SE LEVEL BIT WIDTH LECTED DESCRIPTION NRZ TTL V 0 5v FULL NRZ L Vo 2V FULL NRZ M Vo 2V FULL UNI RZ V 0 2V HALF BIP RZ V V 0 2V HALF RZ AMI V V 0 2V HALF BiO L Vo 2V HALF DICODE V V 0 2V FULL DUOBINARY V V 0 2V FULL TABLE DMK 1 Default threshold settings are V approx 1V V approx 1V Vo approx OV Z MODULATION OUTPUT The Z MODULATION output provides a pulse at the DECISION POINT These pulses may be viewed on the scope screen or may be connected to the scope s Z modulation input Refer to the TECHNICAL DETAILS SECTION regarding setting up Z modulation if required BASIC SPECIFICATIONS Digital waveform inputs two IN1 and IN2 Digital waveform outputs two OUT1 and OUT2 Input Output levels depend upon the waveform format selected TTL 5V OV Unipolar 2V OV Bipolar 2V Waveform format selection by 10 position rotary switch SW1 Waveform formats supported NRZ TTL NRZ L NRZ M UNI RZ BIPOLAR RZ RZ AMI BIPHASE L DICODE DUOBINARY Bit Clock input B CLK TTL level nominally 2kHz operational 250Hz to 3 5kHz performance not specified Bit Clock output B CLK synchronised to the OUTput waveform negative Bit Clock edge aligned with each new output bit Decision point span gt 90 of bit width with 2kHz B CLK DECISION POINT control selection NTernal or External by switch SW2 DECISION POINT control continuous by front panel k
49. MS1 User Manual 35 If an AC voltage is applied to the meter as in SPECTRUM ANALYSER APPLICATIONS then the meter pointer will attempt to faithfully track the varying voltage swings The meter s pointer will only respond to DC and very low frequency signals It is the inertia of the mechanical movement that provides this very low frequency lowpass filter action When using the module in SPECTRUM ANALYSER APPLICATIONS it is important to calculate the conversion sensitivity of the system before attempting to determine absolute voltage readings Refer to the SPECTRUM ANALYSER experiment in the Communication Systems Modelling with TIMS student text for a detailed discussion on conversion sensitivity SETTING UP THE SPECTRUM UTILITIES MODULE The analog panel meter can be used to make both absolute voltage and relative amplitude measurements Both measurement methods have a similar setting up procedure Absolute Voltage Measurements i SPECTRUM UTILITIES settings Turn the PCB mounted trimmer RV1 fully clockwise and set the front panel sensitivity selector switch to x1 The FULL SCALE DEFLECTION is now 2V ii Setting another DC Voltage Reference Using the VARIABLE DC VOLTAGE module set and measure the maximum voltage required on your oscilloscope For example 0 25V DC Next apply this reference voltage to the SPECTRUM UTILITIES module s IN socket Adjust trimmer RV1 for the panel meter to indicate FULL SCALE DEFLECTION Relativ
50. NAL S 100kHz TTL output to the SAMPLER S clock input 3 Patch the ADDER S output to the HARD LIMITER S input 4 Patch the HARD LIMITER S output to the SAMPLER S input 5 Patch the SAMPLER S analog output to one of the MULTIPLIER S inputs Patch the SAMPLER S ADAPTIVE CONTROL output to the MULTIPLIER S other input 6 Patch the MULTIPLIER S output to the INTEGRATOR S input 7 Finally patch the INTEGRATOR S output to the ADDER S second input This completes the Adaptive Delta Modulator When viewing signals around the modulator it is advisable to trigger the scope with the input 2kHz sinewave TIMS AMS1 User Manual 17 DELTA DEMODULATION UTILITIES one bit differential pulse code modulation DPCM Three independent building blocks are provided which in conjunction with other TIMS modules can be used to investigate different methods of recovering the message from data generated by the simple Delta Modulator the Delta Sigma Average Modulator or the Adaptive Delta Modulator Both clock rate and step size can be varied to match that of the modulator DELTA DEMOD UTILITIES INTEGRATOR INTEGRATOR INPUT OUTPUT INTEGRATOR LPF INPUT LPFoutTuT RC LPF Or TTL OUTPUT ANALOG OUTPUT O ADAPTIVE a oapme CONTROL como OUTPUT TTL DATA INPUT CLOCK SELECT CLOCK INPUT SAMPLER FRONT PANEL USE INTEGRATOR INPUT s OUTPUT INP
51. NPUT OUTPUT OUTPUT SELECT VARIABLE PULSE INPUT 1 OUTPUT 1 OUTPUT SELECT J2 INPUT 2 OUTPUT 2 LOOP FILTER INPUT EXTERNAL ener CLOCK INPUT 1 BPF 1 OUTPUT FRONT PANEL INPUT 2 BPF 2 OUTPUT INTERNAL CLK EXTERNAL CLK CLK SELECT USE BLOCK DIAGRAM DIVIDE BY N The DIVIDE BY N is a general purpose digital divider It accepts a standard TTL level signal at the input and outputs a standard TTL level signal The PCB mounted DIP switch SW2 is used to select the division factor as illustrated in the table below SW2 1 A SW2 2 B DIV MODE OFF OFF divide by 8 OFF ON divide by 4 ON OFF divide by 2 ON ON divide by 1 invert A typical application for the DIVIDE BY N may be as part of a Phase Lock Loop PLL system TIMS BITCLOCK REGEN User Manual 78 TRANSITION DETECTOR The TRANSITION DETECTOR will produce a TTL level output pulse for every transition in logic level of the input digital sequence The input sequence must be TTL level Operation of the TRANSITION DETECTOR is such that the input sequence is delayed using a clocked flip flop The exclusive OR circuit then performs the equivalent of a multiplication operation The width of the output pulse is dependent upon the width of the monostable s pulse The PCB mounted jumper J12 allows the user to select either a fixed pulse width FIX or a manually adjustable pulse width VAR The fixed pulse width monostable optimizes the TRANSITI
52. OAO INVERTER INPUT OUTPUT DIVIDER DIVIDER INPUTS OUTPUTS Tene O00000 FRONT PANEL USE i DIGITAL INVERTER and LOGICAL HI INPUT where n 1 2 3 0r4 BLOCK DIAGRAM OUTPUT The digital INVERTER only accepts standard TTL level digital signals The LOGICAL HI outputs approximately 5V and is intended only for connection to digital inputs ii DIVIDERS The six independent digital dividers may be used in any combination to achieve the division ratio required BASIC SPECIFICATIONS Inputs amp Outputs TTL level digital signals Input Frequency Range 0 to 300kHz TIMS AMS1 User Manual 96 QUADRATURE UTILITIES Three independent functions are provided two independent multipliers and an independent adder Each MULTIPLIER allows two analog signals X t and Y t to be multiplier together The resulting product is scaled by a factor of approximately 1 2 The ADDER allows two input signals A t and B t to be added together in adjustable proportions G and g QUADRATURE UTILITIES MULTIPLIER 1 X kXY ANALOG INPUTS O y OUTPUT A D GA gB ANALOG O eee INPUTS O OUTPUT B o gt MULTIPLIER 2 ANALOG O INPUTS Or OUTPUT X kXY y FRONT PANEL BLOCK DIAGRAMS USE i MULTIPLIER 1 and MULTIPLIER 2 Each multiplier has two inputs The inputs and outputs are DC coupled The k factor a scaling parameter associated with four quadrant multipliers is approximately one half It is defined wit
53. OCK INPUT The clock input CLK accepts a TTL level signal It must be synchronised with the incoming q amp i M level signals though its frequency must be the bit clock rate of the output data This data bit clock may be regenerated locally or for maintaining simplicity of the experiment may be stolen from the M LEVEL ENCODER module s clock input source For example if the M LEVEL ENCODER module is being clocked by the 8 3kHz TTL level signal at the MASTER SIGNALS module then the M LEVEL DECODER module may also be clocked by this 8 3kHz signal CLOCK INPUT RANGE SETTING In order to optimize performance of the user variable decision point a PCB mounted RANGE jumper must be set to correctly match the input clock frequency Set the RANGE jumper to LO for clock frequencies up to 4kHz For clock frequencies above 4kHz set the RANGE jumper to HI CONSTELLATION SELECT STANDARD MODE Two front panel CONSTELLATION SELECT switches are used to match the encoding format selected at the M LEVEL ENCODER module On the left side a 2 position switch selects between either a circular phase or square amplitude array On the right side 3 position switch selects the number of points in the constellation 4 8 or 16 The table below lists switch settings required for decoding the six STANDARD constellations Front Panel Switches Constellation Front Panel Switches Constellation Left Right Selected Left Right Selected 4 point 4 PSK
54. ON DETECTOR s operation for use with the LINE CODE ENCODER module s standard 2 083kHz bit clock An adjustable pulse width monostable is also available to allow the user to determine the effect of different pulse widths on the operation of the TRANSITION DETECTOR under various conditions The pulse width is varied using the PCB mounted trimmer labeled VARY PULSE WIDTH RV1 Adjusting the trimmer varies the output pulse width from approximately 10us to 500us In a bit synchronisation system the output of the TRANSITION DETECTOR would normally pass to a bandpass filter or phase lock loop LOOP FILTER The LOOP FILTER is intended for use in Phase Lock Loop PLL applications such as demonstrating PLL bit sync derivation It is a conventional passive Type 1 second order loop structure as illustrated below The factory selected component values are also given ia Label Value R50 9kiR as R53 1k9R C18 100nF C18 I Second order loop Please note that the loop filters input and output have active buffering using op amp circuits this is not illustrated in the above figure Also note that PLLs are classified according to Type based on the number of poles of the loop transfer function at the origin The order of the loop refers to the highest degree of the polynomial of the characteristic equation 1 G s H s Ref Digital Communications with Fibre Optics and Satellite Applications Harold B Killen Prentice H
55. ONNECTION Antenna Output Attach the antenna s coaxial cable directly to an oscilloscope or spectrum analyser to view the signals received by the ANTENNA Amplified Antenna Output Attach the antenna s coaxial cable directly to the 100kKHz RX ANTENNA UTILITIES module s ANTENNA INPUT Use the RX AMP MONITOR output to view or demodulate the received signals The gain of the AMPLIFIER can be adjusted by varying the PCB mounted trimmer RV1 Receiving a Broadcast TIMS Signal Ensure that the PCB mounted MODE selector switch SW1 is in the NORMAL position Attach the ANTENNA s coaxial cable directly to the 100kKHz RX ANTENNA UTILITIES module s ANTENNA INPUT Use the 100kHz BPF s OUT socket to view or demodulate the received signals It is instructive to compare this amplified and filtered output signal with those obtained previously BASIC SPECIFICATIONS ANTENNA Antenna Type tuned wire wound loop antenna Feed low impedance coaxial cable with BNC type connector Resonant Frequency approx 100kHz Usable Frequency Range 75kHz to 125kHz 100kHz RX UTILITIES MODULE Amplifier Gain x100 to x1000 typ Amplifier Usable Frequency Range 10Hz to 1MHz BPF Usable Frequency Range 90kHz to 110kHz TIMS AMS1 User Manual 108 FIBRE OPTIC TRANSMITTER A fibre optic transmitter which converts electrical signals into optical signals in the visible spectrum Any analog or digital signal that can be generated on TIMS may
56. OUT is not active in this mode ii EMBEDDED Mode In EMBEDDED mode the TIMS BLOCK CODE DECODER module will search and extract the embedded code from the incoming serial data In this mode the BLOCK CODE DECODER module will also output the resulting extracted frame synchronisation signal at FS OUT Note that the TIMS PCM ENCODER module embeds a uniquely defined 0 1 0 1 repeating sequence within the digitised code words Four search length options are provided In each case the BLOCK CODE DECODER searches for the selected number of consecutive frame synchronisation bits that is consecutive 0 1 0 1 transitions before locking on The number of consecutive search bits is selected by PCB mounted switch SW3 as follows CONSECUTIVE SW3a SW3b SEARCH BITS OFF OFF 32 bits OFF ON 64 bits ON OFF 128 bits ON ON 256 bits PCM DECODER synchronisation search length options Once the preselected number of consecutive frame synchronisation bits has been found the BLOCK CODE DECODER module locks onto and monitors the synchronisation sequence If the sequence is lost the BLOCK CODE DECODER module maintains the previous lock position until a new valid lock position is found TDM MODE There is no difference between decoding an encoded single channel data stream to decoding an encoded TDM data stream with the BLOCK CODE DECODER module Only one BLOCK CODE DECODER module is required to decode
57. S Two operating modes are provided STANDARD and SPECIAL The SPECIAL operating mode is only used for decoding BPSK signals the STANDARD operating mode is used for all other decoding formats STANDARD OPERATING MODE STANDARD operating mode is automatically enabled by holding the M LEVEL DECODER module s front panel handle and plugging the module directly into the TIMS rack TIMS AMS1 User Manual 87 SPECIAL OPERATING MODE BPSK MODE To switch the M LEVEL DECODER module to the SPECIAL operating mode for decoding BPSK signals only then i remove the M LEVEL DECODER module from the TIMS rack ii press the HUNT push button and while keeping the HUNT push button depressed plug the module into the TIMS rack iii Confirm that the HUNT LED immediately starts and continues flashing slowly approximately one flash per second The slow regular flashing of the HUNT LED indicates that the M LEVEL DECODER module is operating in the SPECIAL mode INPUT SIGNALS STANDARD MODE Three input signals are required for standard operation multi level encoded signals q i and the data bit clock CLK INPUTS q amp i The peak to peak amplitude of the q amp i signals must be approximately 2 5V for optimum decoding performance Hence when setting up experiments always ensure that the amplitudes of the signals being presented to the q amp i inputs are correctly adjusted using the gain or amplitude controls of the preceding modules CL
58. S amp H1 Sample amp Hold The input signal is sampled held and output after the S amp H2 occurrence of each positive CLK edge 1 amp H1 Integrate amp Hold The input signal is integrated over the period of the I amp H2 CLK signal At the occurrence of each positive CLK edge the integrator value is transferred to a hold circuit updating the value at the output The integrator is then dumped and a new integration period commences 1 amp D1 Integrate amp Dump The input signal is integrated over the period of the 1 amp D2 CLK signal During the occurrence of each READY pulse the integrator is dumped and a new integration period is commenced The integrator output is available at the channel s front panel output terminal TIMS AMS1 User Manual 68 ii Integrator time constants The following table summarizes the components and values associated with the integrator time constant of each channel Channel __Integrator s R Integrator s C Comments 1 amp D1 330kohm R7 470pF C4 Fixed RC 1 amp D2 330kohm R26 470pF C34 Jumper J1 open only C34 selected A470pF C44 Jumper J1 shorted adds C44 to C34 jumper at the IN position IMPORTANT NOTE The integrator both integrates and inverts the input signal PULSE WIDTH MODULATION FUNCTIONS The sampling and integrating block also provides a pulse width modulation PWM function on channel 1 1 amp D1 PWM mode is selected using the PCB mount rotary switch SW1
59. S level bipolar signals The output is a TTL level HI 5V if the input signal is a positive voltage A negative voltage at the input will result in the output being a TTL level LO OV LOWPASS FILTERS Two independent lowpass filters a DATA FILTER and a CARRIER FILTER are provided to simplify the implementation of various CDMA receiver structures The DATA FILTER is a 7th order Butterworth lowpass filter with a cut off frequency of approximately 2kHz The CARRIER FILTER is a 7th order Butterworth lowpass filter with a cut off frequency of approximately 120kHz BASIC SPECIFICATIONS VARIABLE DIGITAL DELAY Delay Ranges 1uS to 10uS and 100uS to 1mS continuously variable with each range Input and Output TTL level only PSEUDO NOISE SEQUENCE GENERATOR CLK Input more than 1MHz TTL level RESET Inputs positive going TTL level pulse or front panel push button to reset the sequence SEQUENCE Output TIMS level bipolar length of up to 214 1 bits SYNC Output positive going TTL level pulse is output at the beginning of the sequence Sequence Selection via PCB mounted 10 position rotary switch ZERO CROSSING DETECTOR Input bipolar Output TTL level LOWPASS FILTERS CARRIER Filter approx 120kHz 7th order Butterworth DATA Filter approx 2kHz 7th order Butterworth TIMS AMS1 User Manual 105 100kHz TX ANTENNA A loop antenna to broadcast signals at or near the TIMS carrier frequency of 100kHz A single BUFFER AMPLIFIER is normally
60. SEQUENCE GENERATOR 1 Connect a TTL clock to the M CLK input For example use 8 3kHz from the MASTER SIGNALS module 2 Patch B CLK output to the SEQUENCE GENERATOR module s CLK input 3 Patch the SEQUENCE GENERATOR module s data output either X or Y to the ENCODER S DATA input 4 Press the ENCODER module s RESET push button Repeat this step whenever the M CLK signal is disconnected or interrupted 5 All the Line Codes are now generated and available simultaneously B Using the ENCODER with the DECODER and the SEQUENCE GENERATOR 1 Connect a TTL clock to the M CLK input For example use 8 3kHz from the MASTER SIGNALS module 2 Patch the ENCODER S B CLK output to the SEQUENCE GENERATOR module s CLK input 3 Patch the SEQUENCE GENERATOR module s data output to the ENCODER S DATA input 4 Connect a bit clock to the DECODER S input In a simple test system just patch the ENCODER S B CLK output to the DECODER S B CLK input 5 Select one of the ENCODER s waveform outputs and patch it to the corresponding DECODER input 6 Resetting the ENCODER DECODER module pair Two equivalent methods i For AUTOMATIC RESETTING patch the ENCODER S RESET input to the DECODER S RESET output Depress either the ENCODER S or DECODER S RESET push button once ii For MANUAL RESETTING depress the ENCODER S RESET push button keeping it depressed now depress and immediately release the DECO
61. TIMS AMS1 User Manual 58 Constraint Length The constraint length v of a convolutional code is defined 2 as one plus the past inputs affecting the current outputs NOTE Different definitions of constraint length can be found in the literature on convolutional coding 2 However in all cases constraint length is a measure of the memory within the encoder CODE 1 Code 1 is always defined in the literature as a constraint length v 3 convolutional code Beware that its structure may be represented with either two or three storage elements CODE 2 Referring to the above definition for constraint length CODE 2 would be classified as a constraint length v 4 convolutional code Note that it was defined by G Ungerboeck in 3 and 4 as being a constraint length v 3 convolutional code TEST SEQUENCE The TEST CODE mode may initially be used to assist users in familiarisation with the operation of convolutional encoders Most importantly TEST CODE mode is provided as a method of achieving automatic branch word synchronisation at the convolutional decoder In TEST CODE mode the data presented to the on board encoder circuit is internally switched from the data sequence at the DATA input to an internally generated test data sequence The internal test data sequence is a stream of logical one s 1 1 1 1 etc which provides a uniquely defined and easily identifiable output code sequence The following are the expected outp
62. TRIG input line is actually tied by a pull down resistor to ground GATE INPUT LEVEL The GATE input level can be selected at switch SW1 The default position is LO when using the TIMS PULSE COUNTER module GATE TIMES The output GATE time is determined by a preselected count of input clock pulses The number of clock pulses counted is selected initially by the PULSE COUNT front panel rotary switch The Monostable operates under three modes determined by DIP switch SW2 and jumper J1 Normal Mode Under normal mode four GATE times are available 10 104 10 and 10 clock pulses To select Normal Mode both halves of SW2 must be ON and jumper J1 must be in NORM position Extended Mode Under Extended Mode the pulse count selected at the front panel PULSE COUNT rotary switch can be multiplied by 2 4 or 8 This gives a further 12 available GATE times 2x 10 4x 108 8 x 10 clock pulses 2x 104 4x 104 8 x 104 clock pulses 2x 10 4x 105 8 x 10 clock pulses 2x 10 4x 10 8 x 10 clock pulses See the COUNT MULT table next to switch SW2 for required switch positions Jumper J1 must be in NORM position Expanded Mode Expanded Mode is provided specifically to allow the Monostable to be used in applications with 100kHz bit clock frequency using a 8 333kHz clock signal in place a 100kHz clock signal The 8 333kHz TTL signal available from the MASTER SIGNALS module is connected to the clock input instead of the 100kHz TT
63. UT _ OUTRUF CLIPPER 1 CLIPPER 1 CLIPPER 1 INPUT OUTPUT INPUT OUTPUT INPUT OUTPUT 33kHz BPF 33kHz BPF Ze INPUT OUTPUT 33 3kHz BPF BLOCK DIAGRAM FRONT PANEL USE The FM UTILITIES module enables wideband FM signals to be generated based on an Armstrong modulator and two harmonic also known as frequency multipliers The Armstrong modulator is patched together using four other TIMS modules and provides a wideband phase modulated signal whose deviation is then increased by the harmonic multipliers Each harmonic multiplier is made up of a clipper also known as a limiter and a bandpass filter The clipper generates a series of harmonics and the bandpass filter passes only the third harmonic The FM UTILITIES module provides the first harmonic multipliers 33 3kKHz bandpass filter The second harmonic multiplier uses the 100KHz CHANNEL FILTERS module 100kHz bandpass filter FM MASTER SIGNALS The FM MASTER SIGNALS block provides a synchronised 11 1kHz sinewave carrier signal required for the Armstrong modulator The 100kHz input will accept a standard TIMS level signal either analog or digital level from the TIMS MASTER SIGNALS module s 100kHz CARRIER output The FM MASTER SIGNALS 11 1kHz SINE output is a standard analog TIMS level signal exactly one ninth the frequency of the input signal TIMS FM UTILITIES User Manual 81 CLIPPER or LIMITER 1 amp 2 Two independent CLIPPERs are provided which will amplify any an
64. UT OUTPUT INPUT CLK TTL DATA ANALOG DATA ADAPTIVE CONTROL BLOCK DIAGRAM The INTEGRATOR input accepts standard TIMS level signals The input signal is integrated with INVERSION and then output Its gain can be varied by selecting different switch settings at SW2 this has the effect of varying the modulators STEP SIZE The INTEGRATOR S feedback capacitor value is 47nF C2 The input resistors value is 5k6R R11 when DIP switch SW2A and SW2B are both OFF If DIP switch SW2A is ON it will shunt another 5k6R resistor R12 across the input resistor similarly if DIP switch SW2B is ON it will shunt a 1kK5R resistor R13 across the input resistor Either switches may be ON or OFF in any combination RC LPF This is a simple RC circuit with a cut off frequency of about 2kHz Both input and output are buffered SAMPLER The SAMPLER input takes in a TTL level signal which it samples and then outputs at regular CLOCK intervals The incomming Delta Modulated data is connected to the SAMPLER S INPUT TIMS AMS1 User Manual 18 The CLOCK input must be synchronised and in phase with the incomming data It may be locally regenerated or stolen from the modulator The front panel toggle switch selects the clock rate of the SAMPLER division of the input CLOCK by 1 2 or 4 is carried out internally by the SAMPLER Both TTL and analog DATA are output The TTL DATA is available for reference purposes only The bip
65. all Inc DUAL BPFs Two independent tuneable high Q bandpass filters are provided to demonstrate both bandpass filter jitter reduction and bandpass filter bit sync derivation Each filter accepts and outputs standard TIMS level signals Both filters have the same fixed Q of 22 The centre frequency of each filter is controlled by a digital clock signal The frequency of the digital clock signal is 50 times the centre frequency of the BPF The source of the digital clock signal may be either the internal on board crystal oscillator or an external oscillator TIMS BIT CLOCK REGEN User Manual 79 The PCB mounted DIP switch SW1 is used to select each filter s clock source The internal crystal derived clock INT CLK is optimized for use with the LINE CODE ENCODER module s standard 2 083kHz bit clock The external clock EXT CLK may be used to tune the centre frequency of either or both of the filters between 1kKHz and 5kHz The external TTL level clock source is applied via the front panel EXT CLK input The table below lists all possible combinations of clock source for both filters SW1 1 SW1 2 BPF 1 BPF 2 SOURCE SOURCE OFF OFF External External OFF ON External Internal ON OFF Internal External ON ON Internal Internal Please note that when BPF 1 and BPF 2 both have External Source selected both filters receive the same clock signal via the front panel EXT CLK input BASIC SPECIFICAT
66. all logical ones RESET clears encoder registers and resets internal clocks CLK SYNC allows the encoder s bit cock to be aligned with other modules bit clocks TIMS AMS1 User Manual 57 TECHNICAL DETAILS CONVOLUTIONAL ENCODER CODEWORD BIT FORMATS The relationship between the various clock signals and data waveform are illustrated below M CLK S CLK DATA IN SERIAL OUTPUTS B CLK DATA OUT codeword bit 1 bit 0 0 1 1 1 OUT2 PARALLEL OUTPUTS NOTE PHASE DELAY OF 1 2 B CLK BIT 1 BIT O OUTa NOTE The parallel output bits are delayed in phase with respect to the serial output bits by half a cycle of the bit clock B CLK CONVOLUTIONAL ENCODER TERMS AND DEFINITIONS Systematic and Nonsystematic Convolutional Codes In brief convolutional codes can be classified as systematic or nonsystematic depending on whether or not the input data sequence appears directly within the output encoded sequence A systematic convolutional code is one in which the input data sequence appears directly as part of the output encoded sequence Code Rate Both CODE 1 and CODE 2 are rate R 1 2 codes which defines the codes as producing two encoded bits for each input data bit
67. alog TIMS level signal and then clip or limit the amplitude of the amplified signal to a preset level Each clipper s output level can be preset by a PCB mounted continuously variable gain control GAIN 1 and GAIN 2 33 3kHz BPF The 33 3kHz bandpass filter is a 6th order filter with a 6kHz passband The BPF accepts and outputs standard TIMS level signals BASIC SPECIFICATIONS FM MASTER SIGNALS Input 100kHz standard TIMS level analog or TTL level digital signal Output 11 1kHz sinusoidal standard TIMS level analog signal Input Output Frequency Ratio 9 1 CLIPPER 1 amp 2 Number two totally independent clipper circuits Input bipolar analog signal Output bipolar analog signal amplitude set by GAIN control GAIN Control sets CLIPPER output from about 1Vpk pk to a maximum of 7Vpk pk Frequency Range gt 100kHz 33 3kHz BPF Input amp Output standard TIMS level analog signals Type sixth order inverse Chebyshev with 1dB passband ripple Centre Frequency 33 3kHz Passband approx 6kHz Stopband Attenuation 55dB TIMS FM UTILITIES User Manual 82 M LEVEL ENCODER m QAM amp m PSK CONSTELLATION GENERATOR MULTI LEVEL ENCODER SECTION GUIDE USER INFORMATION 83 BASIC SPECIFICATIONS 85 TECHNICAL DETAILS 85 QUICK OPERATING GUIDE 86 A continuous sequence of TTL level data bits is grouped into sets of L bits where L 2 3 or 4 Each set of L bits is encoded to form a pair of M level baseband signals
68. be transmitted FIBRE OPTIC TX dnp STYLE FIBRE OPTIC OUTPUT E INPUT SIGNAL LEVEL SELECT SIGNAL ANALOG neure gt OUTPUT INPUT We BLOCK DIAGRAM FRONT PANEL USE The signal to be transmitted is applied to the INPUT terminal The INPUT SIGNAL switch must be selected to identify the input signal s format TTL refers to TTL level signals and ANALOG refers to TIMS level signals The input signal frequency may be from DC up to 1MHz FIBRE OPTIC DEVICE AND CONNECTOR A high radiance LED is used to convert the electrical signal to a visible red light signal The LED s peak spectral output is approximately 660nm The output connector is a dnp type which interfaces to a sheathed 1mm polymer fibre optic cable Typical attenuation for the polymer fibre is typically 200dB km at 665nm and 1500cB at 820nm CAUTION the polymer fibre cable has a minimum bend radius of 100mm BASIC SPECIFICATIONS Input TTL level digital signal or standard TIMS level analog signal switch selectable Input Frequency Range DC to lt 1MHz Fibre Optic Device high radiance GaAsP LED 660nm peak spectral output Fibre Optic Connector System single way dnp dry non polish system Fibre Optic Cable 1mm polymer single core fibre optic cable sheathed in polyethylene TIMS AMS1 User Manual 109 FIBRE OPTIC RECEIVER A fibre optic receiver which converts optical signals in the visible spectrum into electrical si
69. by the DECISION MAKER module The DECISION MAKER module accepts up to two TTL unipolar or bipolar level baseband digital signals and a synchronised bit clock The input signals are sampled at a point determined by the user and are output as clean digital signals along with an in phase and synchronised bit clock Using an oscilloscope the decision point is displayed as a bright marker on the input digital waveform DECISION MAKER INPUT 2 outPuT 2 IN 2 rer DECISION ne POINT CONTROL oam DECISION oe DECISION POINT POINT Z MOD VOLTAGE MARKER Vi l INPUT Vin zmop OUTPUT s B CLK INPUT 1 O O ouTPUT 1 IN1 OUT1 IN 1 BIT CLOCK O IN PHASE OUT 1 INPUT NZ BIT CLOCK B CLK FRONT PANEL BLOCK DIAGRAM USE INPUTS IN1 amp IN2 IN1 and IN2 will each accept an incomming digital signal If only one digital signal is available then either input may be used leave the unused input unconnected When a digital signal is connected to each input then both signals must have the same waveform format Ensure the amplitudes of the input digital signals are within TIMS standard limits of 2V bipolar 2V amp OV unipolar and 5V amp OV TTL TIMS AMS1 User Manual 6 WAVEFORM FORMAT SELECTION The correct waveform format must be selected prior to using the DECISION MAKER MODULE The user has a choice of eight bipolar and unipolar waveforms Line Codes as well as standard TTL waveforms Set switch SW1 to
70. de of the 4 AM TCM symbols 3 1 Using and oscilloscope observe the output of the MULTIPLIER module and verify that the 4 AM TCM symbols have 4 voltage levels 3 2 Adjust the BUFFER AMPLIFIERS module s variable gain control such that the span of the whole symbol set is 3V peak to peak 4 This completes the setting up of the TCM modulator B Setting up the TCM Demodulator Decoder 1 The modules required for the TIMS 4 AM TCM demodulator are patched together as illustrated in Figure 2 on the first page of this chapter 2 The DSP and INTEGRATE amp DUMP modules require setting up and mode selection as follows 2 1 Set up the DSP and AIB modules as described on the previous page 2 2 Set up the INTEGRATE amp DUMP module s operating modes as follows Select I amp H1 integrate and hold mode at the rotary PCB mount switch SW1 and select I amp D2 integrate and dump mode at rotary switch SW2 Select the Adjust the DELAY control range to 60us 500us via SW3 SW3 1 B set ON and SW3 2 A set OFF 3 For initial familiarization purposes make direct connections between the TCM modulator and demodulator Later a noisy channel may be simulated using other TIMS modules 3 1 Pass a stolen clock from the CONVOLUTIONAL ENCODER module s S CLK output to the INTEGRATE amp DUMP module s digital delay B CLK input 3 2 Pass a stolen carrier from the modulators BUFFER AMPLIFIER module output to the demodulators PHASE SHIFTER i
71. der 103 Part Ill SPECIAL APPLICATIONS MODULES USER INSTRUCTIONS 100kHz Tx Antenna 106 100kHz Rx Antenna Utilities 107 Fibre Optics Transmitter 109 Fibre Optics Receiver 110 TIMS INTRODUCTION TIMS OVERVIEW TIMS is a telecommunications modelling system It models mathematical equations representing electrical signals or block diagrams representing telecommunications systems TIMS is primarily a hands on rather than demonstration style teaching system which combines both the theoretical and practical aspects of implementing systems We are confident that TIMS will provide the student with a clearer understanding of the concepts behind telecommunications theory Physically TIMS is a dual rack system The top rack accepts up to 12 Eurocard sized compatible black boxes or modules The lower rack houses a number of fixed modules as well as the system power supply The modules are very simple electronic circuits which function as basic communications building blocks Each module fixed or plug in has a specific function basic functions fall into three general categories Signal Generation oscillators etc Signal Processing multipliers filters etc Signal Measurement frequency counter Modules are patched together via the front panel sockets using interconnecting leads to model the system under investigation TIMS OPTIONAL ADVANCED MODULES The TIMS Advanced Modules add to the range and depth of experiments t
72. e Amplitude Measurements i SPECTRUM UTILITIES settings Turn the PCB mounted trimmer RV1 fully clockwise and set the front panel sensitivity selector switch to x1 ii Use Apply a reference signal and adjust RV1 for appropriate indication say half or full scale indication Other signals can now be measured as a ratio of the reference signal SPECTRUM ANALYSER QUICK OPERATION GUIDE The following is intended only as a quick reference for making use of this module in SPECTRUM ANALYSER APPLICATIONS For detailed theoretical and user information please refer to the SPECTRUM ANALYSER experiment in the Communication Systems Modelling with TIMS student text SETTING UP THE SPECTRUM ANALYSER i Turn the PCB mounted trimmer RV1 fully clockwise and set the front panel sensitivity selector switch to x1 Follow the above procedures for setting up for Relative Voltage Measurements If Absolute Voltage Measurements are required then the conversion sensitivity must calculated after the spectrum analyser has been patched together ii Four other BASIC modules are required to create a spectrum analyser the MULTIPLIER VCO VARIABLE DC VOLTAGE and FREQUENCY COUNTER Before proceeding please refer to the TIMS 301 Users Manual s VCO chapter for information on FINE FREQUENCY CONTROL of the VCO using the VARIABLE DC VOLTAGE module iii After the VCO has been set up for FINE FREQUENCY CONTROL operation patch the VCO s analog outp
73. e second step is to use the PWM output signal to clock the TWIN PULSE GENERATOR module s clock input CLK Ensure that SINGLE mode is selected on the TWIN PULSE GENERATOR module s PCB mount slide switch The TWIN PULSE GENERATOR module s outputs then both produce a pulse position modulation signal Take care to ensure that the TWIN PULSE GENERATOR module s pulse width is not set wider than the repetition time of the PWM pulses TIMS AMS1 User Manual 69 INTEGRATE amp DUMP block function waveforms The waveforms below illustrate the operation and timing of the sampling and integrating block s functions INPUT SIGNAL 7 SAMPLE amp HOLD i INTEGRATE Lo nnna Le N TENE E EE as amp DUMP gt x a gt BASIC SPECIFICATIONS DIGITAL DELAY Input amp Output TTL level digital signals Clock input lt 15kHz Variable delay range 10us to 1 5ms in 4 switch selectable ranges INTEGRATE amp DUMP Operating modes integrate amp dump integrate amp hold sample amp hold PWM Channels 2 channels simultaneously operating with a common bit clock with the exception of PWM mode which is only available on channel 1 1 amp D1 Analog inputs and outputs standard TIMS level Clock input lt 500Hz to gt 15kHz standard TTL level Integrator integration commences on the negative edge of the READY signal When hold is selected the integrator output is sampled on the positive edge of the clock signal Dumping commence
74. e summarised below FRAME 0 0 0 D3 D2 Di Do FS frame bit no bit7 bit6 bit5 bit4 bit3 bit2 biti bito MSB LSB Frame length 8 bits Bit 0 least significant bit frame synchronisation bit FS Bits 1 to 4 message bits Dx bit 4 is the most significant message data bit Bits 5 to 7 zero redundant data bits ii Output Frame The BLOCK CODE ENCODER module outputs codeword bits in the following frame format FRAME C2 Ci Co D3 D2 D1 Do FS frame bit no bit7 bit6 bit5 bit4 bit3 bit2 biti bitO MSB LSB Frame length 8 bits Bit 0 least significant bit frame synchronisation bit FS Bits 1 to 4 message bits Dx bit 4 is the most significant message data bit Bits 5 to 7 check bits Cx used for encoding Parity Bit is bit 5 C1 amp C2 are set to zero Hamming and Cyclic check bits are bits 5 6 and 7 TIMS AMS1 User Manual 47 FRAME SYNCHRONISATION The BLOCK CODE ENCODER module uses the frame synchronisation signals generated by preceding modules such as the PCM ENCODER module Note that the BLOCK CODE ENCODER module does not generate any separate or independent frame synchronisation signals and does not alter the embedded frame synchronisation bit bit 0 i External Frame Synchronisation Signal When an external frame synchronisation signal is required then the FS terminal at the PCM EN
75. ed to automatic upper position Note that decoding does not occur in the upper switch position iii The CONVOLUTIONAL DECODER AIB module acknowledges that it has achieved synchronisation by turning on the AIB module s LED iv Select the middle position at the CONVOLUTIONAL DECODER for correct decoding v Return the CONVOLUTIONAL ENCODER module s mode switch to NORMAL Changing the switch to the lower position will illustrate incorrect decoding The above steps must be repeated if any of the clock siganis at the encoder or if the clock signal to the decoder are interrupted or reset BASIC SPECIFICATIONS Modules Required TIMS DSP HS or TIMS DSP RB and TIMS AIB Firmware Software Required EPROM pair or floppy disk with CODE 1 and or CODE 2 decoder program Decoder Technique Implemented Viterbi algorithm with hard decision inputs Code Clock Input typ 2kHz TTL level synchronised and in phase with the code sequence Code Sequence Input TTL level convolutionally encoded sequence Data Output decoded TTL level data sequence Clock Output typ 1kHz TTL level synchronised and in phase with the data sequence Branch Word Synchronisation automatic requiring test code sequence and manual control TIMS AMS1 User Manual 64 SETTING UP THE DSP MODULES Please refer to the DSP User Manual for detailed setting up and user information The following is intended only as quick reference guide Setting up the TIMS DSP HS amp
76. ement larger multi channel CDMA schemes The sequences are stored in EPROM and an optional TIMS Interactive program allows the user to generate a file for programming custom EPROMs MULTIPLE RESET SEQUENCES PN SOURCE CLK s X OR ANALOG amp SYNC INPUTS TTL OUTPUTS RESET PN OUTPUT BIPOLAR CLOCK SYNC PULSE X OR INPUTS TH X OR ANALOG amp RESET INPUTS TTL OUTPUTS BN RESET PN OUTPUT CLK OUT CLOCK SYNC PULSE SYNC BIPOLAR FRONT PANEL X OR INPUTS TTL BLOCK DIAGRAM USE PSEUDO NOISE SEQUENCE GENERATORS PN1 amp PN2 The two sequence generators are identical Each has two TTL level inputs and two TTL level outputs Inputs CLK is the sequence s external bit clock input The input clock signal s frequency can range from a few hertz to over 1MHz The sequence may be reset by depressing the front panel push button or by applying a TTL level HI at the RS RESET input Outputs The sequence outputs are labeled PN1 and PN2 respectively TIMS AMS1 User Manual 100 The SYNC pulse is used to identify one complete repetition of the sequence The TTL level HI pulse at the SYNC output coincides with the first bit of the sequence Sequence Selection 10 switch selectable multiple length sequences of up to 2141 bits are available These are stored in EPROM and are selected via the PCB mounted switches SW1 and SW2 Each sequence generator on the module is provided with its own EPROM The standard EPROM provided PNSQ1 1 contain
77. en in NORMAL mode the encoder module maps and outputs the input data sequence into the selected convolutional code either CODE 1 or CODE 2 TEST CODE Mode The TEST mode may initially be used to assist users in familiarisation with the operation of convolutional encoders Most importantly TEST CODE mode is provided as a method of achieving automatic branch word synchronisation at the convolutional decoder In TEST CODE mode the data presented to the module s encoder circuit is internally switched from the data sequence at the DATA input to an internally generated test data sequence The internal test data sequence is a stream of logical one s 1 1 1 1 etc which provides a uniquely defined and easily identifiable output code sequence RESET Position The RESET position clears the convolutional encoder s registers and restarts the internal clocking circuits RESET need only be depressed once after the M CLK and or CLK SYNC if CLK SYNC is being used signals are first connected OUTPUT SIGNALS One set of serial and one set of parallel encoded data output signals are provided as well as two clock signals Note that the serial and parallel outputs simultaneously present the encoded data from the same encoder CODE 1 or CODE 2 whichever happens to be selected Serial Output The serial encoded output sequence is presented in two signal level formats the DATA output is TTL level and the OUT2 output is bipolar standard TIMS le
78. er signal sources to be recorded and replayed A pcb mounted jumper J9 controls the input signal selection either MIC EXT or EXT only For MIC only operation leave the EXT input is not connected HEADPHONES A pair of telecommunications style headphones is provided to allow the user to listen to the recorded messages by patching any one of the SPEECH module s outputs to the HEADPHONE AMPLIFIER in the TIMS System Unit BASIC SPECIFICATIONS CHANNEL 1 and CHANNEL 2 Bandwidth 300Hz to 3 400Hz fixed Record length 0 to 32 seconds each channel Sampling rate 8kHz LIVE Filters four user selectable settings i none ii 300Hz HPF iii 3 6kHz LPF iv 300Hz HPF and 3 6kHz LPF INPUTS MiCrophone in built electret type EXTernal standard TIMS level 2V pk HEADPHONES Included for use with HEADPHONE AMPLIFIER TIMS AMS1 User Manual 99 MULTIPLE SEQUENCES SOURCE CDMA ENCODER Four independent functional blocks are provided i two independent pseudo noise PN sequence generators each with 10 switch selectable multiple length sequences of up to 2144 bits ii two independent Exclusive OR functions with analog and digital level outputs to implement modulo 2 addition Each PN sequence generator and EX OR pair is used to implement a Direct Sequence Spread Spectrum DSSS channel Two DSSS channels 2 channel CDMA can be implemented per module additional MULTIPLE SEQUENCES SOURCE modules may be used to impl
79. er Manual 86 M LEVEL DECODER BPSK m QAM amp m PSK CONSTELLATION DECODER MULTI LEVEL DECODER SECTION GUIDE USER INFORMATION Standard Mode 87 USER INFORMATION BPSK Mode 91 BASIC SPECIFICATIONS 93 TECHNICAL DETAILS 94 QUICK OPERATING GUIDE 95 A pair of baseband multi level encoded signals q amp i originally generated by the M LEVEL ENCODER module are sampled decoded into unique groups of bits length L and output as a continuous serial data stream The output data is synchronised and in phase with the bit clock The input signals q amp i are sampled at a point determined by the user Using an oscilloscope the decision point is displayed as a bright marker on the input waveforms The sampled and held q amp i signals are also output Q amp I Seven different decoding formats are available The six standard operating mode formats 4 QAM 8 QAM 16 QAM 4 PSK 8 PSK amp 16 PSK are selected via front panel switches The seventh decoding format BPSK is enabled via a special operating mode of the M LEVEL DECODER module M LEVEL DECODER M PSK 4 8 amp 16 M QAM k POINT SELECT SELECT DECISION POINT DECISION HUNT LED DECISION POINT AUNT PE Z MODULATION POINT LZ OUTPUT HUNT INPUT q M level to Z MOD data set M LEVEL SAMPLED amp i converter DATA INPUTS HELD SIGNAL CLK CLOCK DECODED BLOCK DIAGRAM INPUT DATA OUTPUT FRONT PANEL STANDARD OPERATING MODE USE OPERATING MODE
80. error rate in digital systems EDN August 20 1990 4 G Ungerboeck Channel coding with multilevel phase signals IEEE Trans Information Theory vol IT 28 Jan 1982 5 G Ungerboeck Trellis coded modulation with redundant signal sets Part Introduction and Part Il State of the art EEE Communications Magazine vol 25 no 2 Feb 1987 we HS YH WH TIMS AMS1 User Manual 61 CONVOLUTIONAL DECODER CONVOLUTIONAL DECODER SECTION GUIDE USER INFORMATION 62 BASIC SPECIFICATIONS 64 SETTING UP THE DSP MODULES 65 QUICK OPERATING GUIDE 66 A continuous sequence of data bits is generated from a continuous sequence of convolutionally encoded bits The decoder is implemented with the TIMS Digital Signal Processing modules set TIMS DSP and TIMS AIB The convolutional decoding method used the Viterbi Algorithm with hard decision input A bit clock must be provided which is synchronised and in phase with the incoming encoded sequence The decoder also outputs a separate bit clock which is synchronised and in phase with the decoded data Branch word synchronisation can be controlled manually via a front panel switch As well automatic branch word synchronisation can be achieved using the CONVOLUTIONAL ENCODER module s TEST CODE mode TIMS AIB CONVOLUTIONAL FRONT PANEL DECODER FACILITIES FUNCTIONS ENCODED DECODED 3 position switch Branchword SEQUENCE DATA synchronisa
81. g maximal length 7 a4 long maximal length 8 27 1 short maximal length 9 27 1 short maximal length Custom Sequences As the 10 sequences are stored in a standard commercially available EPROM it is possible to remove the socketed EPROM supplied and replace it with an EPROM containing up to 10 custom designed sequences Custom sequences can be designed using the optional MATLAB based TIMS Interactive program Sequence Generation and Analysis This TIMS Interactive allows the user to design and analyze maximal length non maximal length TIMS AMS1 User Manual 104 and Gold codes of up to 214 1 bits Sequence Generation and Analysis also generates an Intel Hex file from these sequences which can be downloaded to an EPROM programmer to program a custom EPROM When designing custom sequences it is important to note that the MULTIPLE SEQUENCES SOURCE module allows 2 different sequence lengths Sequences at switch positions 0 1 2 3 6 7 must all be of the same length and sequences at the other switch positions 4 5 8 amp 9 must all be of the same length In the standard EPROM these are identified as long and short respectively Note that long and short may be of equal length for cases where 10 sequences of the same length are required ZERO CROSSING DETECTOR The ZERO CROSSING DETECTOR is used as a level translator to convert a recovered bipolar data stream to a TTL level signal The input accepts standard TIM
82. gnals Output signals may be analog or digital level FIBRE OPTIC RX PHOTO DETECTOR PRE AMP GAIN dnp STYLE FIBRE OPTIC INPUT OUTPUT SIGNAL LEVEL SELECT ANALOG INPUT 77 OUTPUT BLOCK DIAGRAM FRONT PANEL USE The signal received is applied to the FIBRE OPTIC INPUT connector The OUTPUT SIGNAL switch must be selected to identify the output signal s required format TTL refers to TTL level signals and ANALOG refers to TIMS level signals The GAIN knob controls the gain to the photo detector s pre amplifier It may be used to control the amplitude of the OUTPUT signal FIBRE OPTIC DEVICE AND CONNECTOR A high speed PIN photo diode is used to convert a visible red light signal to an electrical signal The PIN photo diode s peak spectral output is approximately 800nm BASIC SPECIFICATIONS Fibre Optic Device high speed low noise PIN photo diode 800nm peak spectral input Fibre Optic Connector System single way dnp dry non polish system Fibre Optic Cable 1mm polymer single core fibre optic cable sheathed in polyethylene Output TTL level digital signal or standard TIMS level analog signal switch selectable Output Frequency Range DC to lt 1MHz TIMS AMS1 User Manual 110
83. h respect to the OUTPUT of the multiplier and may be measured experimentally ii ADDER The adder input gains G and g can be adjusted via pcb mounted trimmers RV1 and RV3 respectively Note that these two trimmers have knobs to allow for finger adjustment RV1 varies G and RV3 varies g BASIC SPECIFICATIONS MULTIPLIER 1 and MULTIPLIER 2 Inputs amp Outputs DC coupled Bandwidth approx 1MHz Characteristic k X t Y t k is approx 1 2 ADDER Gain range 0 lt G amp g lt 1 5 Bandwidth approx 500kHz TIMS AMS1 User Manual 97 SPEECH MODULE The SPEECH module allows speech and audio signals to be recorded and replayed Three independent channels are provided CHANNEL 1 CHANNEL 2 and LIVE The module includes an in built microphone An EXTernal input is also provided for recording externally generated signals The recorded channels signals are band limited to 300Hz and 3 4kHz The LIVE channel has user selectable LPF and HPF CH1 RECORD PLAY CONTROL CH2 RECORD PLAY CONTROL MICROPHONE EXTERNAL INPUT USE SPEECH MODULE RECORD CH 1 CH1 OUTPUT PLAY RECORD eg CH2 OUTPUT PLAY LIVE OUTPUT LIVE HPF CONTROL LIVE LPF CONTROL FRONT PANEL CHANNEL 1 and CHANNEL 2 Channels 1 and 2 will each record up to 32 seconds of speech and sounds from the common MICrophone input RECORD or PLAY GHI record disable SW1 we amp aR ove LIVE FUNCTIONAL BLOCK DIAGRAM To
84. hat can be carried out by students and lecturers on the TIMS system These Advanced Modules fall into two main groups Digital Signal Processing TMS320C50 and TMS320C10 based Specialised Modules with specific building block functions This manual covers a particular group of optional Specialised Modules only TIMS AMS1 User Manual 1 SYSTEM CONVENTIONS All TIMS modules conform to the following mechanical and electrical conventions A FRONT PANEL SOCKETS Signal interconnections are made via front panel 4mm sockets Sockets on the LEFT HAND SIDE are for signal INPUTS All inputs are high impedance typically 56k ohms Sockets on the RIGHT HAND SIDE are for signal OUTPUTS All outputs are low impedance typically 330 ohms YELLOW sockets are only for ANALOG signals ANALOG signals are held near the TIMS standard reference level of 4V pk pk RED sockets are only for DIGITAL signals DIGITAL signals are TTL level 0 to 5 V GREEN sockets are all common or system GROUND Note that input and output impedances are intentionally mismatched so that signal connections may be made or broken without changing signal amplitudes at module outputs B PLUG IN MODULES Any plug in module may be placed in any of the 12 positions of the upper rack All modules use the back plane bus to obtain power supply only the DSP modules not part of the BASIC SYSTEM use the bus to transfer signals The modules are designed so that they may be
85. he long wave and medium wave frequency ranges The UTILITIES module includes a high gain broad band amplifier and a separate 100kHz band pass filter 100kHz RX ANTENNA TILITIES er ANTENNA ANTENNA ANTENNA INPUT R amp P input RX AMP MONITOR Saris AMPLIFIER OUTPUT 100kHz BPF BPF TEST ANALOG OUT INPUT OUTPUT TEST IN BLOCK DIAGRAM FRONT PANEL USE POSITIONING The ANTENNA should always be placed on top of the TIMS 301 system unit Ensure that the TIMS 301 s front feet are folded back so the top of the system unit is not sloping Always keep in mind that the loop antenna has directional characteristics Maximum sensitivity is in the direction of the loop s opening perpendicular to the plane of the loop The TX and RX antennas should always be directly facing each other the planes of their loops should be in parallel The received signal is amplified and available at the RX AMP MONITOR output The gain of the amplifier is continuously variable from x100 to approx x1 000 PCB mounted trimmer RV1 varies the amplifier s gain The amplified signal can also be filtered by the module s 100kHz BPF The TEST IN socket is provided to allow the BPF to be characterised if necessary TEST IN is directly connected to the BPF input when the PCB mounted MODE switch SW1 is in the TEST position The PCB mounted MODE switch SW1 must otherwise be left in the NORMAL position TIMS AMS1 User Manual 107 C
86. iddle Manual Decodes Initially branch bit as normal randomly selected lower Manual reverse Decodes Branch bits of middle as reverse reversed TIMS AMS1 User Manual 63 Manual Operation Manual operation occurs when decoding commences immediately after the RESET of the DSP module and the 3 position switch is in either the middle or lower position Under manual operation the branchword bit orientation is initially selected at random and decoding commences The user will need to switch between the middle and lower switch positions to determine which is the correct branchword bit orientation for decoding Alternating between the middle and lower switch positions will alternate the branch word bit orientation The incorrect position will result in continuous and severe errors in the decoded data Automatic Operation As illustrated in the CONVOLUTIONAL ENCODER module s user information the encoded sequence of a known test code is well defined and therefore allows the CONVOLUTIONAL DECODER to identify the orientation of bits O and 1 within the serial codeword Automatic operation requires initial transmission of a test code sequence by the CONVOLUTIONAL ENCODER module to which the CONVOLUTIONAL DECODER synchronises itself Automatic operation requires the following setting up procedure i The CONVOLUTIONAL ENCODER module s mode switch must be switched to TEST CODE ii The CONVOLUTIONAL DECODER AIB module is then switch
87. ing signals around the modulator it is advisable to trigger the scope with the 2kHz sinewave message signal DELTA SIGMA MODULATOR This modulator s implementation is almost identical to the simple Delta Modulator The only difference in patching is that the INTEGRATOR is moved to between the ADDER and HARD LIMITER 1 Take an ADDER module and using the scope adjust each input s gain to unity 2 Patch the 2kHz sinewave from the MASTER SIGNALS module to one of the ADDER S inputs Also patch the MASTER SIGNAL S 100kHz TTL output to the SAMPLER S clock input 3 Patch the ADDER S output to the INTEGRATOR S input 4 Patch the INTEGRATOR S output to the HARD LIMITER S input 5 Patch the HARD LIMITER S output to the SAMPLER S input 6 Finally patch the SAMPLER S analog output to the ADDER S second input This completes the Delta Sigma Modulator When viewing signals around the modulator it is advisable to trigger the scope with the 2kHz sinewave message signal ADAPTIVE DELTA MODULATOR This modulator s implementation is almost identical to the simple Delta Modulator The only difference in patching is that a MULTIPLIER is inserted between the SAMPLER and the INTEGRATOR 1 Take an ADDER module and using the scope adjust each input s gain to unity TIMS AMS1 User Manual 16 2 Patch the 2kHz sinewave from the MASTER SIGNALS module to one of the ADDER S inputs Also patch the MASTER SIG
88. input signals are required for correct operation DATA and M CLK The third input CLK SYNC is only used under special conditions M CLK Input The master clock M CLK must be a TTL level signal such as the TIMS MASTER SIGNALS module s 8 33kKHz SAMPLING CLOCK output TIMS AMS1 User Manual 53 DATA Input The DATA input requires a TTL level sequence of digital data which is synchronised and in phase with the encoder module s own sampling bit clock S CLK Digital data may be obtained from the SEQUENCE GENERATOR module or from the PCM ENCODER module NOTE The CONVOLUTIONAL ENCODER module s S CLK output must be used as the input clock signal to the module providing the digital data sequence to the CONVOLUTIONAL ENCODER module CLK SYNC Input The external bit clock synchronisation input CLK SYNC requires a TTL level clock signal This input is reserved only for the situation where there are one or more digital modules operating simultaneously with the CONVOLUTIONAL ENCODER module and all these module s bit clocks are independently derived from a higher frequency master clock signal such as the TIMS MASTER SIGNALS 8 33kHz SAMPLING CLOCK Connection to the CLK SYNC input and usage is discussed later under the heading BIT CLOCK SYNCHRONISATION CODE SELECTION Two codes are provided for encoding the data Selection is made via a front panel toggle switch CODE 1 is a simple nonsystematic convolutional code with rate R 1 2 and
89. inst the same cut off frequency by adjusting the TUNEABLE LOWPASS FILTER s cut off frequency to match each channel s cut off frequency EYE DIAGRAMS Observing the EYE DIAGRAMS of digital data signals passing through the above selection of filters will illustrate each filters hence channel s performance TIMS AMS1 User Manual 4 BASIC SPECIFICATIONS Input coupling AC or DC channels 1 to 4 Channel responses Channel 1 straight through Channel 2 Butterworth 7th order Channel 3 Bessel 7th order Channel 4 OpFil Linear Phase 7th order Stop band attenuation approx 40dB 4kHz Passband ripple 0 5dB OpFil Linear Phase filter is a proprietary filter design having a sharp roll off characteristic with a linear phase response in the passband This filter was designed by Optimum Filters Pty Ltd Sydney Australia TIMS AMS1 User Manual 5 DECISION MAKER DECISION MAKER SECTION GUIDE USER INFORMATION BASIC SPECIFICATIONS TECHNICAL DETAILS QUICK OPERATION GUIDE ooog 4 Digital signals may become corrupted by noise and interference in the communications channel After demodulation or receiver filtering a corrupted digital signal would need to be squared and converted to a clean digital waveform with an associated in phase bit clock so that further digital processing decoding or message recovery can be performed The tasks of squaring the corrupted digital signal and aligning the bit clock can be carried out
90. it will shunt a 1kK5R resistor R13 across the input resistor Either switches may be ON or OFF in any combination HARD LIMITER With a threshold of OV GROUND the HARD LIMITER is in fact a zero crossing detector There is no inversion The input accepts standard TIMS level signals the output is a TTL level waveform SAMPLER The SAMPLER input takes in a TTL level signal which it samples and then outputs at regular CLOCK intervals The INPUT of the SAMPLER is usually connected directly to the HARD LIMITER S output The CLOCK input is usually connected to the TIMS 100kKHz MASTER SIGNALS TTL output The front panel toggle switch selects the clock rate of the SAMPLER division of the input CLOCK by 1 2 or 4 is carried out internally by the SAMPLER Both TTL and analog DATA are output The TTL DATA is standard TTL level 5V and OV The analog DATA level is approximately 5V and 5V The ADAPTIVE CONTROL output can be used at any time to observe when slope overload occurs It is also used when implementing the Adaptive Delta Modulator The ADAPTIVE CONTROL signal becomes active at the third bit if three successive bits have been all ONEs 111 or all ZEROs 000 Under normal mode the ADAPTIVE CONTROL voltage is approximately 2V DC During slope overload conditions the ADAPTIVE CONTROL becomes active by increasing to approximately 4V DC SETTING UP FOR EACH DELTA MODULATOR SCHEMES When implementing each of the three Delta Mod
91. ly provide error detection for single bit errors and errors of odd numbers of bits The ERROR CORRECTED LED and output is only active for codes that can detect and correct errors for these codes the ERROR DETECT output is not active When an error is detected and correction attempted the CORRECTED LED will flash and a single pulse will occur at the CORRECTED output For example the Hamming Code will provide single bit error detection and correction and so only uses the ERROR COR RECTED LED and output TIMS AMS1 User Manual 50 Note that the pulse width of the output ERROR INDICATION signals is very narrow and hence the intensity of the LED indicator may not be easily discernible if there are very few or sporadic errors Hence errors should normally be counted and monitored electronically The LED indicators are primarily intended to alert the user to severe and gross system errors FRAME SYNCHRONISATION Two methods are used to recover frame synchronisation EXTERNAL makes use of a separate TTL level input signal connected to EXTERNAL FS and EMBEDDED extracts the embedded code within the digitised serial data The method required is selected by front panel switch EXTERNAL or EMBEDDED i EXTERNAL Mode In EXTERNAL mode the separate frame synchronisation input signal EXTERNAL FS must normally be low and should only go high for one bit period coincident with the least significant bit of the PCM code word bit 0 Note that FS
92. n be moved by either front panel control INTernal control or by external DC voltage applied to input Vin EXTernal control Sliding switch SW2 located on the PCB selects INTernal or EXTernal control mode The DECISION POINT can be displayed on an oscilloscope as a bright marker by viewing the input digital waveform and connecting the Z MODULATION output to the scope The DECISION POINT always moves with respect to the input bit clock So in order to see the bright DECISION POINT marker move across the digital waveform or EYE DIAGRAM then the scope MUST be triggered by either the input sequence s SYNC or by the INPUT bit clock SPECIAL NOTE The RZ and Biphase Line Codes may be refered to as HALF WIDTH waveforms while the other Line Codes including TTL would be refered to as FULL WIDTH waveforms Care must be taken when moving the DECISION POINT across the HALF WIDTH waveforms as only half the bit width usually carries useful information In the HALF WIDTH case determining which half of the bit width the DECISION POINT has been positioned can seen by observing the Bit Error Rate or by viewing the actual input waveform rather than by the EYE DIAGRAM See TABLE DMK 1 for the list of waveforms and their width description TIMS AMS1 User Manual 7 Table DMK 1 lists the supported waveforms their thresholds output levels and bit width descriptions WAVEFOR
93. n regarding the sampling theorem when selecting the relative frequencies of both Vin and CLK PCM DATA The TTL level digitised data is output serially TIMS PCM code words are in standard offset binary format with the first 7 bits allocated for data coding and the least significant bit allocated for the frame synchronisation code TIMS AMS1 User Manual 38 Three digitising schemes are provided for comparison purposes Selection is made via front panel switch a 7 bit linear b 4 bit linear and c 4 bit companded either TIMS A4 Law or TIMS 4 Law Note that selection between TIMS A4 Law or TIMS 4 Law is made via jumper selector on the PCM ENCODER module s PCB FRAME SYNCHRONISATION Two methods are used to indicate frame synchronisation a separate TTL level output signal FS and an embedded code within the digitised serial data The frame synchronisation signal FS is normally low and only goes high for one bit period at the time of the least significant bit of the PCM code word bit 0 The frame synchronisation signal is also embedded within the digitised code word as the least significant bit bit 0 The code selected is a repeating 0 1 0 1 sequence This is a unique sequence which corresponds to the Nyquist frequency of the sampled signal and so is otherwise considered a disallowed state SYNCHRONISED SINUOUS TYPE MESSAGE A variable frequency output signal MESSAGE synchronized to the input bit cl
94. nob INT or 0 to 5V DC EXTERNAL input signal EXT at Vin Z MODULATION level three modes available with variable level control see Technical Details Z MODULATION pulse width 2uS typical TIMS AMS1 User Manual 8 TECHNICAL DETAILS Z MODULATION Three Z modulation modes are supported with variable level control Each mode is selected by positioning jumper J1 Trimmer RV2 controls the level of the output signal MODE A position J1A normal intensity 5V bright intensity OV MODE B position J1B normal intensity OV bright intensity 5V MODE C postition J1 C normal intensity OV bright intensity 5V In each case trimmer RV2 will control the level of the bright intensity DECISION POINT THRESHOLDS The three voltage thresholds V V and Vo are set by fixed resistors These can be changed if required for specific applications as follows V 15 x R2 R2 R5 default values R2 10kR R5 680R V 15 x R6 R6 R3 default values R3 10kR R6 680R Vo 15 x R4 R4 R1 default values R1 56kR R4 100R BIT CLOCK The DECISION MAKER module was specifically designed to operate with the TIMS standard 2 083kHz available from the MASTER SIGNALS module The 2 083kHz sinewave must be converted to TTL using the UTILITIES module s COMPARATOR Alternatively the 8 33kHz TTL signal can be divided by 4 using the LINE CODE ENCODER module Other clock rates will function but the DECISION POINT adjus
95. nput Ensure the PHASE SHIFTER module s PCB mount sliding range selection switch is set to the HI range 3 3 Patch the modulator s output directly to the demodulator s input TIMS AMS1 User Manual 76 4 Local carrier phase adjustment The local carrier s phase requires adjustment for maximum amplitude of the received multilevel data 4 1 Vary the PHASE SHIFTER module s COARSE and FINE control knobs while observing the INTEGRATE amp DUMP module s output at 1 amp D1 Recall that integrate and hold mode must be selected for channel 1 amp D1 Adjust for a nominal 3V peak to peak amplitude of the multilevel data 5 Bit clock alignment Since each TCM symbol is a DC voltage integrating over only one symbol within a bit clock cycle will result in a single ramp within that single bit clock cycle this represents correct alignment between the bit clock and the multilevel encoded data stream Integrating over two symbols within a bit clock cycle will result in the occurrence of two opposing ramps within some bit clock cycles this would signify incorrect alignment Hence the INTEGRATE amp DUMP module s second channel 1 amp D2 may be used to achieve correct alignment between the bit clock and the data stream 5 1 Make an additional connection from the output of the MULTIPLIER to the 1 amp D2 input 5 2 Vary the INTEGRATE amp DUMP module s DELAY control while observing the 1 amp D2 output 5 3 Adjust the INTEGRATE amp
96. ntrol Under TDM mode one PCM DECODER module becomes the the main control module referred to as the MASTER and the other operates as the SLAVE This is achieved by patching a lead from the TDM CONTROL MASTER output of one module to the TDM CONTROL SLAVE input of the other module Any module may become the MASTER or the SLAVE Note that the MASTER can only control one SLAVE module never connect more than one SLAVE to a MASTER module ii PCM Data The PCM DATA input of each of the two modules must be patched together This becomes the combined input for the module pair Note also that each module must be supplied with the same bit clock CLK iii Frame Synchronisation Always ensure that both modules have the same frame synchronisation mode selected either EXTERNAL or EMBEDDED FS OUT at the MASTER module may be used for viewing or utilising the frame synchronisation of the TDM decoding system iv TDM Operation Always ensure that the digitising scheme s selected at the PCM DECODER modules corresponds to the digitising scheme s selected at the PCM ENCODER modules BASIC SPECIFICATIONS Input PCM DATA serial TTL level data stream in offset binary format Input Format 8 bits including frame synchronisation bit as LSB Digitising Formats 7 bits linear 4 bits linear and 4 bits companded Companded Formats TIMS 4 bit A4 Law and TIMS 4 bit U4 Law PCB selectable Bit Clock Input lt 10kHz TTL level positive edges of CLK amp PC
97. ock CLK is also provided to allow detailed observation of the input signal and resulting digital code words The frequency of this MESSAGE signal may be varied by setting the PCB mounted switch SW2 as follows SYNCHRONISED MESSAGE FREQUENCY SETTINGS Ratio of MESSAGE frequency SW2a SW2b to bit clock CLK OFF OFF 1 32 OFF ON 1 64 ON OFF 1 128 ON ON 1 256 Available MESSAGE frequency options TDM MODE Two PCM ENCODER modules may be connected in parallel with the appropriate control signal to establish a two channel Time Division Multiplexing system Thus two analog signals are each digitised and then transmitted along a single digital data line i TDM Control Under TDM mode one PCM ENCODER module becomes the main control module referred to as the MASTER and the other operates as the SLAVE This is achieved by patching a lead from the TDM CONTROL MASTER output of one module to the TDM CONTROL SLAVE input of the other module Any module may become the MASTER or the SLAVE Note that one MASTER can only control one SLAVE module never connect more than one SLAVE to a MASTER module TIMS AMS1 User Manual 39 ii PCM Data The PCM DATA output of each of the two modules must be patched together This becomes the combined output for the module pair Note that only the PCM DATA outputs are designed to be patched together as they are open collector outputs Note also that each module m
98. olar analog DATA output is utilised by the other demodulator blocks The output level is approximately 5V and 5V The ADAPTIVE CONTROL output can be used at any time to observe when slope overload occurs It is also used when implementing the Adaptive Delta Demodulator The ADAPTIVE CONTROL signal becomes active at the third bit if three successive bits have been all ONEs 111 or all ZEROs 000 Under normal mode the ADAPTIVE CONTROL voltage is approximately 2V DC During slope overload conditions the ADAPTIVE CONTROL becomes active by increasing to approximately 4V DC SETTING UP FOR THE ADAPTIVE DELTA DEMODULATOR A TIMS MULTIPLIER module is inserted at the INTEGRATOR S input the signal to the INTEGRATOR is multiplied by the voltage from the ADAPTIVE CONTROL output Hence providing effective control over the INTEGRATOR S gain TIMS AMS1 User Manual 19 BASIC SPECIFICATIONS INTEGRATOR Input frequency range 400Hz to 10kHz Output integral of the input with inversion Gain user selectable by DIP switch RC LPF Cut off frequency approximately 2kHz Input and output buffered standard TIMS level SAMPLER Input TTL level digital signal Digital output TTL level digital signal Analog output bipolar digital signal approx 5V and 5V Clock input lt 1kHz to gt 500kHz Clock selection divides input clock by 1 2 or 4 ADAPTIVE CONTROL output 2V normal mode approx 4V adaptive mode ADAPTIVE CONTROL coincidence conditi
99. on 000 or 111 adaptive signal is active at the third bit if three successive ONEs or three successive ZEROs have occured INTEGRATOR OVERVIEW The DELTA DEMODULATOR S INTEGRATOR is identical to the INTEGRATOR of the DELTA MODULATOR Please refer to the INTEGRATOR OVERVIEW section of the DELTA MODULATION UTILITIES chapter for details TIMS AMS1 User Manual 20 QUICK OPERATION GUIDE CLOCKED DELTA DEMODULATOR WITH INTEGRATOR 1 Patch the incomming TTL data to the SAMPLER S input Also patch the MASTER SIGNAL S 100kHz TTL output to the SAMPLER S clock input 2 Patch the SAMPLER S analog output to the INTEGRATOR S input 3 Finally patch the INTEGRATOR S output to a lowpass filter say the TIMS TUNEABLE LPF This completes the Delta Demodulator CLOCKED DELTA DEMODULATOR WITH SIMPLE RC This demodulator implementation is almost identical to the previous one The only difference is that the INTEGRATOR is replaced with a simple RC LPF UNCLOCKED DELTA DEMODULATORS These may be implemented by connecting the TTL data directly to an INTEGRATOR or RC LPF ADAPTIVE DELTA DEMODULATOR This demodulator s implementation is almost identical to the first clocked Delta Demodulator The only difference in patching is that a MULTIPLIER is inserted between the SAMPLER and the INTEGRATOR 1 Patch the incomming TTL data to the SAMPLER S input Also patch the MASTER SIGNAL S 100kHz TTL output to the SAMPLER S clock input 2
100. ong and short respectively Note that long and short may be of equal length for cases where 10 sequences of the same length are required EXCLUSIVE OR LOGIC GATES Two independent exclusive OR gates are provided Their TTL level inputs A and B are exclusive ORed and simultaneously output as TTL level and standard TIMS level bipolar signals The relationship between the TTL level and TIMS level outputs is TTL level OUTPUT TIMS level OUTPUT OV 2V 5V 2V TIMS AMS1 User Manual 101 BASIC SPECIFICATIONS PSEUDO NOISE PN SEQUENCE GENERATORS Number of Sequence Generators 2 independent PN sequence generators CLK Input more than 1MHz TTL level RESET Inputs positive going TTL level pulse or front panel push button to reset the sequence SEQUENCE Output TTL level length of up to 214 1 bits SYNC Output positive going 1 bit wide TTL level pulse is output at the beginning of the sequence Sequence Selection via PCB mounted 10 position rotary switch EXCLUSIVE OR GATES Number of X OR Gates 2 independent EX OR gates Inputs A amp B TTL level Outputs continuous X OR result both TTL level unipolar and standard TIMS level bipolar signals TIMS AMS1 User Manual 102 CDMA DECODER Four separate functional blocks used in realizing various DSSS and CDMA receiver structures are provided i a variable digital delay ii a pSeudo noise PN sequence generator with 10 switch selectable multiple length
101. ous stream of decoded data bits TTL level amp Q Outputs sampled amp held representation of the input signals with offset OPERATING MODES selected by method of power up STANDARD for decoding six front panel selectable constellations BPSK for decoding BPSK signals only CONSTELLATION SELECT front panel switch selectable offering either circular or rectangular 4 8 and 16 point constellations Decision boundaries preset and fixed for each constellation refer to diagrams in User Manual DECISION POINT control continuous regions with region selected by HUNT function HUNT control steps DECISION POINT across adjacent regions of the symbol to be sampled HUNT Input TTL level positive going edge HUNT LED has three functions i Slow regular flashing indicates BPSK operation mode ii Turns on to confirm HUNT function has been enabled iii Indicates invalid data at DATA output i amp q Input offset control PCB trimmer adjustable 0 25V Z MODULATION Output three modes available with variable level control Z MODULATION pulse width 2uS typical TIMS AMS1 User Manual 93 TECHNICAL DETAILS TRIMMING INPUT SIGNAL OFFSETS The signals at the Q amp I outputs are the actual sampled and held representations of the q amp i input signals which are presented to the internal decoder s analog to digital converter Any accumulated DC offset in either the q or i branch may be viewed at the Q amp I outputs and nulled by adjusting the respective PC
102. put serial TTL level CLK Input up to 10kHz TTL level OPERATING MODES PCB jumper selectable NORM converts sets of input DATA into pairs of multi level signals DEMO for testing and displaying constellations only CONSTELLATION SELECT front panel switch selectable offering either circular or rectangular 4 8 and 16 point constellations ibranch amp Qbranch Outputs 2 3 4 or 8 level depending upon constellation selected 2 5Vpk pk TECHNICAL DETAILS The signal state space diagrams for the six available constellations follow Note that the data bits representing each symbol are arranged in a Grey Code sequence 701 au Pn me n 11010 e1001 e110 e100 r ae 11006 e 1000 01008 e 0000 e010 e000 01010 e0001 Lag 01119 0011 oot me 0110 0010 4 PSK 8 PSK 16 PSK 1001 1000 0000 0001 e01 00 e000 e001 e e e e010 e011 1011 1010 0010 0011 e 1111 1110 0110 0111 e e 110 111 1101 1100 0100 0101 11 10 100 101 e e 5 e 4 QAM 8 QAM 16 QAM When viewing the above constellations on an oscilloscope it is important to note that the horizontal axis in the above diagrams is i and the vertical axis is q HINT To assist in determining the correct orientation of the viewed constellation presenting a logical high to the DATA input of the M LEVEL ENCODER module e g press the RESET push button on the SEQUENCE GENERATOR module will only display the 11 111 or 11
103. q amp i This q amp i signal pair can be represented as 2L unique points or symbols in a signal state space diagram or constellation Six different encoding formats are available selected via front panel switches for generating 4 QAM 8 QAM 16 QAM 4 PSK 8 PSK amp 16 PSK signals A demonstration mode for viewing constellation displays is also provided M LEVEL ENCODER CONSTELLATION M PSK SELECT M QAM 4 8 amp 16 4 point POINT esa data set qandi SELECT M LEVEL qpranch SERIAL to M level M LEVEL ae OUTPUT DATA converter OUTPUTS SERIAL M LEVEL ibranch DATA DATA n OUTPUT CLOCK BLOCK DIAGRAM CLOCK INPUT cik FRONT PANEL USE OPERATING MODES Two operating modes are provided NORMal and DEMO The PCB mounted jumper J3 is used to set the operating mode NORMal mode provides full functional operation of the module Both DATA and CLK input signals are required for normal operation DEMO mode has limited functional application It is used only for self test and illustration purposes to allow the quick setting up of a constellation display on an oscilloscope Only a clock signal at the CLK input is required the DATA input is unused TIMS AMS1 User Manual 83 INPUT SIGNALS Two TTL level input signals are required for normal operation DATA and CLK The DATA input signal must be synchronised and in phase with the CLK signal CONSTELLATION SELECT Two front panel CONSTELL
104. relationship between the input signal B CLK and the output signal CLK OUT B CLK CLK OUT Valid DELAY control knob adjustment range Caution always ensure that the CLK OUT pulse remains within the B CLK cycle as illustrated above Extending the CLK OUT pulse into the following cycle will cause invalid operation SAMPLING amp INTEGRATING FUNCTIONS The sampling and integrating block provides two identical channels which operate simultaneously with a common sampling clock Each channel 1 amp D1 and 1 amp D2 takes a standard TIMS level analog input The output signals are analog level The two channels require a bit clock for operation which is provided via the CLK input A standard TTL level signal is required The READY output pulse is only used when sample amp hold or integrate amp hold functions are selected The positive edge of the READY pulse occurs immediately after the signal at the 1 amp D1 or 1 amp D2 outputs has been updated and has settled i Mode select Each channel of the sampling and integrating block includes three circuit functions a sampler an integrator and a hold circuit The user can select the configuration of these circuit functions via two PCB mount rotary switches SW1 for channel 1 amp D1 and SW2 for channel I amp D2 The available configurations the corresponding PCB labels and functional descriptions are given below Label Function Description
105. rity pulse to pulse O no pulse BiO L Biphase level Manchester lt bipolar gt 1 transition from high to low in the middle of the bit interval 0 transition from low to high in the middle of the bit interval DICODE NRZ_Dicode nonreturn to zero lt 3 level gt 1 to 0 or O to 1 transition change in pulse polarity 1 to 1 or O to O transition no pulse PRECODED DUOBINARY PARTIAL RESPONSE SIGNALING lt 3 level gt Unlike Line Code encoding Duobinary encoding is a non linear process and so cannot be described by the above coding rules The following model represents the process of Precoded Duobinary encoding Exclusive OR GATE ADDER with level shifting at inputs Figure LCE 1 Precoded Duobinary Model TIMS AMS1 User Manual 27 Illustrating the operation of the Precoded Duobinary model INPUT DATA SEQUENCE xn PRECODING gt Un Xn Un 1 LEVEL SHIFTING bipolar Un Un DUOBINARY CODING RULE Yn Un Una Note the INITIAL condition uo 1R Figure LCE 2 illustrates the above Line Code and Partial Response waveform definitions graphically 1 1 1 1 1 a I t DATA V BIP RZ 0 V V RZ AMIO V V BiO L Manchester V V DICODE NRZ 0 V V DUOBINARY 0 V nee Figure LCE 2 Encoded Waveforms TIMS AMS1 User Manual 28 QUICK OPERATION GUIDE A Using the ENCODER with the PSEUDORANDOM
106. rmatted data is provided by the PCM ENCODER module with 4 bit digitising selected A TTL level FRAME SYNCHRONISATION signal as provided by the PCM ENCODER module An alternative source of digital data and frame synchronisation signals may be obtained from the SEQUENCE GENERATOR module with the optional PCM SIMULATION EPROM installed TIMS AMS1 User Manual 46 CODE SELECTION Three codes are provided for encoding the data Selection is made via a front panel toggle switch The actual codes available depend upon the EPROM version provided Refer to the following table for available codes EPROM CODE 1 CODE 2 CODE 3 VERSION BLKe1 x Even Parity Hamming 7 4 Set Up single bit error detect single bit error correct with Cx bit error detect BLKe2 x Even Parity Hamming 7 4 Odd Parity single bit error detect single bit error correct single bit error detect BLKe3 x Even Parity Hamming 7 4 Cyclic single bit error detect single bit error correct Set Up is provided as a special mode to allow setting up of experiments more easily The PCM DATA frame is passed straight through from PCM DATA input to BLOCK CODE output without alteration PCM and CODEWORD BIT FORMATS i Input Frame The required format at the PCM DATA input is either TIMS PCM ENCODER 4 bit scheme refer to PCM ENCODER module s user instructions in this manual The frame s bit assignments ar
107. rror detection and error correction events TDM Mode compatible with PCM DECODER modules in TDM mode TIMS AMS1 User Manual 52 CONVOLUTIONAL CODE ENCODER CONVOLUTIONAL ENCODER SECTION GUIDE USER INFORMATION 53 BASIC SPECIFICATIONS 57 TECHNICAL DETAILS 58 QUICK OPERATING GUIDE 60 REFERENCES 61 A continuous sequence of data bits is mapped into a continuous sequence of convolutionally encoded bits Two different convolutional encoders are provided one systematic and one nonsystematic Output coded bits are presented in both serial and parallel TTL level format as well as 2 level and 4 level bipolar format Required bit clock signals are generated within the encoder module derived from a single master clock input Provision is made for synchronisation of the encoder bit clock signals with the bit clocks of other clocked modules A test pattern setting is provided to allow automatic branch word synchronisation by the convolutional decoder to the encoder module s output sequence CONVOLUT L ENCODER MODE Oras SELECT beer cope gE O 4 LEVEL OUTPUT SELECT Sima O PARALLEL CODE 2 gito TTL LEVEL CONVOLU SERIAL EXTERNAL BIT OUTPUTS SERIAL TIONAL EN CODEWORD CLOCK SYNC oe DATA CODER R v PARALLEL 2 LEVEL OUTPUT CODEWORD SERIAL DATA O SERIAL OUTPUT CLOCK BIT CLOCK MASTER BIT CLOCK OUT BLOCK DIAGRAM CLOCK INPUT DATA INPUT yak six SAMPLING CLOCK FRONT PANEL USE INPUT SIGNALS Two
108. s on the positive edge of the READY pulse The output of the integrator is inverting Sampler the sampling of the input signal commences on the positive edge of the clock signal and is completed on the positive edge of the READY pulse Ready TTL level pulse lt 10us width Occurs after the hold circuits output has settled TIMS AMS1 User Manual 70 TRELLIS CODED MODULATION DECODER TRELLIS CODE MODULATION DECODER SECTION GUIDE USER INFORMATION 71 BASIC SPECIFICATIONS 74 SETTING UP DSP MODULES 75 QUICK OPERATING GUIDE 76 A continuous sequence of data bits is generated from a continuous sequence of encoded multilevel data bits The input encoded data bits must be obtained from a matched filter or equivalent functional block The TCM DECODER is implemented in two sections i A matched filter implemented with a multiply integrate and dump functional block and ii A soft decision Viterbi decoder implemented with the TIMS Digital Signal Processing modules For completeness the implementation and setting up of the TIMS 4 AM TCM modulator is also briefly described E gt gt STOLEN CLOCK STOLEN CLOCK SEQUENCE ICONVOLUT L MULTIPLIER MULTIPLIER INTEGRATE TIMS320 TIMS320 GENERATOR ENCODER amp DUMP OSP DB AIB OUT gt 4 AM DELAY TEM B CLK CLK OUT B0 7 D 4 LOCAL BIT CLK 2 lt 2 gt DATA gt 1801 RECOVERED re DATAT DATA1 CLK M CLK S CLK CLK READY
109. s sequences of two fixed lengths long and short at the following switch positions SW1 and SW2 SEQUENCE SEQUENCE POSITION LENGTH TYPE 0 alt long maximal length 1 214 4 long maximal length 2 2144 long maximal length 3 214 4 long maximal length 4 27 1 short maximal length 5 27 1 short maximal length 6 alt long maximal length 7 2144 long maximal length 8 27 4 short maximal length 9 27 4 short maximal length Custom Sequences As the 10 sequences are stored in a standard commercially available EPROM it is possible to remove the socketed EPROM supplied and replace it with an EPROM containing up to 10 custom designed sequences Custom sequences can be designed using the optional MATLAB based TIMS Interactive program Sequence Generation and Analysis This TIMS Interactive allows the user to design and analyze maximal length non maximal length and Gold codes of up to 214 1 bits Sequence Generation and Analysis also generates an Intel Hex file from these sequences which can be downloaded to an EPROM programmer to program a custom EPROM When designing custom sequences it is important to note that the MULTIPLE SEQUENCES SOURCE module allows 2 different sequence lengths Sequences at switch positions 0 1 2 3 6 7 must all be of the same length and sequences at the other switch positions 4 5 8 amp 9 must all be of the same length In the standard EPROM these are identified as l
110. se modulators DELTA MODULATION UTILITIES Oss INTEGRATOR TTL OUTPUT HARO LIMITER TTL INPUT sr O TTL DATA O ANALOG DATA CLK 2 O ADAPTIVE lt aowe CONTROL CONTROL OUTPUT INTEGRATOR INPUT HARD LIMITER INPUT CLK CLOCK SELECT CLOCK INPUT SAMPLER FRONT PANEL USE INPUT OUTPUT INPUT TTL OUTPUT INPUT CLK TTL DATA ANALOG DATA ADAPTIVE CONTROL BLOCK DIAGRAM Along with this DELTA MODULATION UTILITIES module and the modules which provide message and clock signals two other standard TIMS modules are required to implement the three different Delta Modulation schemes To implement the simple Delta Modulator or the Delta Sigma Modulator a TIMS ADDER module is also required For Adaptive Delta Modulation both a TIMS ADDER and a TIMS MULTIPLIER module are required TIMS AMS1 User Manual 12 INTEGRATOR The INTEGRATOR input accepts standard TIMS level signals The input signal is integrated with INVERSION and then output Its gain can be varied by selecting different switch settings at SW2 this has the effect of varying the modulators STEP SIZE The INTEGRATOR S feedback capacitor value is 47nF C2 The input resistor s value is 5k6R R11 when DIP switch SW2A and SW2B are both OFF If DIP switch SW2A is ON it will shunt another 5k6R resistor R12 across the input resistor similarly if DIP switch SW2B is ON
111. stant the internal decoder makes a decision as to the state or level of the sample The thresholds or decision boundaries which the internal decoder follows is simply the mid point between both symbols The user has control over the sampling instant via the front panel DECISION POINT control knob The sampling instant is displayed on an oscilloscope as a bright marker via the Z MODULATION output when the i input signal is viewed The sampling instant is moved across each i symbol using the DECISION POINT control knob HUNT INPUT and PUSH BUTTON The HUNT push button and input have no function in BPSK mode and are not used HUNT LED The slow regular flashing of the HUNT LED indicates that the M LEVEL DECODER module is operating In BPSK mode Z MODULATION OUTPUT The Z MODULATION output provides a pulse at the sampling instant These pulses may be viewed on the oscilloscope s screen or may be connected to the oscilloscope s Z modulation input To display the sampling instant connect the M LEVEL DECODER module s Z modulation signal at the front panel BNC connector to the oscilloscope s Z modulation input Refer to the TECHNICAL DETAILS section later in this chapter on setting up the Z modulation facility TIMS AMS1 User Manual 92 BASIC SPECIFICATIONS i amp q Inputs 2 3 4 or 8 level depending upon constellation selected 2 5Vpk pk CLK Input up to 10kHz TTL level synchronised with input symbols DATA Output continu
112. strated below The decision boundaries for each constellation are fixed and cannot be altered by the user 4 QAM 8 QAM 16 QAM Decision boundaries for the 6 STANDARD mode constellations KEY coisi dotted lines represent the 2 5V optimum decoding amplitude limits dashed lines represent the decision boundaries TIMS AMS1 User Manual 89 The user has control over the sampling instant via the front panel DECISION POINT control knob and the HUNT push button and HUNT input The sampling instant is displayed on an oscilloscope as a bright marker via the Z MODULATION output when the q amp i input signals are viewed The sampling instant is moved across each q amp i symbol using both the DECISION POINT control knob and the HUNT push button The DECISION POINT control knob provides access to a limited region of fixed width across the symbol Typically this fixed width is in the order of the width of the data bit clock The HUNT push button and HUNT input will allow the user to step the sampling instant to the next adjacent region within the symbol Thus with the HUNT push button s facility for stepping to each region across the symbol the user is able to gain access to all regions of the symbol with the DECISION POINT knob HUNT INPUT A positive going TTL level signal presented to the HUNT input performs the same function as pressing the
113. t FS OUT is not active in this mode ii EMBEDDED Mode In EMBEDDED mode the TIMS PCM DECODER module will search and extract the embedded code from the incoming serial data In this mode the PCM DECODER module will also output the resulting extracted frame synchronisation signal at FS OUT Note that the TIMS PCM ENCODER module embeds a uniquely defined 0 1 0 1 repeating sequence within the digitised code words Four search length options are provided In each case the PCM DECODER searches for the selected number of consecutive frame synchronisation bits that is consecutive 0 1 0 1 transitions The number of consecutive search bits is selected by PCB mounted switch SW3 as follows CONSECUTIVE SW3a SW3b SEARCH BITS OFF OFF 32 bits OFF ON 64 bits ON OFF 128 bits ON ON 256 bits PCM DECODER synchronisation search length options Once the preselected number of consecutive frame synchronisation bits has been found the PCM DECODER locks onto and monitors the synchronisation sequence If the sequence is lost the PCM DECODER maintains the previous lock position until a new valid lock position is found TIMS AMS1 User Manual 44 TDM MODE Two PCM DECODER modules may be connected in parallel with the appropriate control signal to decode the data generated by two PCM ENCODER modules operating in the Time Division Multiplex mode Thus two analog signals are recovered i TDM Co
114. the encoded TDM data The TDM block encoded data is patched directly to the BLOCK CODE DECODER module s input The BLOCK CODE DECODER module s output is patched directly to each of the two PCM DECODER modules inputs Note that all three modules must be supplied with the same bit clock CLK Refer to the PCM DECODER module s user instruction in this manual regarding TDM mode TIMS AMS1 User Manual 51 BASIC SPECIFICATIONS Block Data Input serial TTL level Block Data Input Format fixed 8 bit frame length with 7 bit codeword plus LSB as embedded frame synchronisation bit 1 2 or 3 most significant bits allocated as check bits depending upon selected code Bit Clock Input typically 2kHz lt 8kHz maximum TTL level positive edges of CLK amp BLOCK CODE DATA coincident Output PCM Data serial TTL level Output PCM Data Format fixed 8 bit frame with 3 most significant bits zero 4 message bits bit 4 is most significant data bit and bit 0 LSB is embedded frame synchronisation bit Frame Synchronisation LINE and EMBEDDED modes LINE Mode synchronisation signal coincident with frame s LSB EMBEDDED Mode search and extract 0 1 0 1 code in LSB of each frame EMBEDDED Mode Search 32 64 128 and 256 consecutive frame synch bits PCB switch Linear Block Codes dependent upon EPROM version installed Parity even Hamming 7 4 single error correction Parity odd Cyclic Error Indication LED and TTL level pulse output of e
115. the required waveform format position SW1 is a PCB mounted ten position rotary switch at the rear of the module BIT CLOCK and OUTPUTS OUT1 amp OUT2 This DECISION MAKER module primarily operates with bit clocks of around 2kHz The input bit clock B CLK must be synchronised to the input digital signal s and so should be either regenerated from an input digital signal or may be stolen from the transmitter The output bit clock B CLK is synchronised and aligned with the output bit stream s in the following manner each new bit occurs on the negative falling B CLK edges The position of the output bit clock s negative edge is determined by the DECISION POINT control DECISION POINT CONTROL The DECISION POINT is the point at which the incomming digital data is sampled At the sampling time a decision is made as to whether the sample is HI or LO and the result is output to the corresponding output OUT1 or OUT2 If a digital signal is present at each input then both are sampled simultaneously the results are also output simultaneously The user has direct control over the position of the DECISION POINT across the bit width The threshold voltages for the decision are set by fixed resistors The threshold voltages are listed in TABLE DMK 1 See TECHNICAL DETAILS SECTION for more information With an input bit clock of 2kHz the DECISION POINT can be moved continuously across more than 90 of the bit width The DECISION POINT ca
116. therefore S CLK B CLK 2 where M CLK is the master input clock B CLK is the serial output bit clock and S CLK is the sampling clock used to generate the input data sequence BIT CLOCK SYNCHRONISATION The CLK SYNC input is reserved only for the situation where there are one or more digital modules operating simultaneously with the CONVOLUTIONAL ENCODER module and all these module s bit clocks are independently derived from the same higher frequency master clock signal The master clock signal is then divided within each module to obtain the required bit clock The relationship between the higher frequency master clock signal and the derived bit clock signals must be 1 4 As a result of the frequency division of the master clock signal the phases of the derived bit clocks among the modules may not necessarily be the same Under these conditions the CLK SYNC signal enables the CONVOLUTIONAL ENCODER module to align the phase of its bit clock to the phase of the other modules bit clocks For example both the LINE CODE ENCODER module and the CONVOLUTIONAL CODE ENCODER module require a master clock signal such as the TIMS MASTER SIGNALS 8 33kKHz SAMPLING CLOCK Each module divides the master signals clock to obtain a 2kHz bit clock When both modules are used simultaneously in the same experiment then their bit clocks must be in phase To align the phases of the two modules i Patch the 8 33kHz master clock to both modules ii Take
117. tion control CODE DATA BIO Input Code clock CLOCK CLOCK TTL Input 1 Encoded sequence input TTL Output 1 Decoded data clock BLOCK DIAGRAM TTL Output 2 Decoded data FRONT PANEL INPUT OUTPUT ASSIGNMENTS USE MODULES REQUIRED The TIMS Digital Signal Processing module set is required either the TIMS DSP HS development board or the TIMS 320 RB run board and the TIMS AIB analog interface board SOFTWARE FIRMWARE REQUIRED The CONVOLUTIONAL DECODER program is available in both EPROM and on floppy disk format Note that the CONVOLUTIONAL ENCODER module includes two different convolutional encoder structures Both the EPROM pair and floppy disk are labeled to identify which convolutional code s decoder CODE 1 and or CODE 2 is implemented TIMS AMS1 User Manual 62 INPUT SIGNALS Two input signals are required for correct operation ENCODED SEQUENCE the AIB module s TTL Input 1 and CODE CLOCK the AIB module s BIO input Both these signals must be clean squared digital signals Note that the TIMS DECISION MAKER module may be required to clean up digital signals that have undergone any kind of distortion CODE CLOCK Input BIO The CODE CLOCK must be a TTL level signal and be synchronised and in phase with the encoded sequence ENCODED SEQUENCE transitions occur on positive CODE CLOCK edges Refer to the timing diagrams illustrated in the CONVOLUTIONAL ENCODER module s user information ENCODED SEQUENCE Inp
118. tment range will be affected If the clock is increased then the range will not extend across the full bit width Conversely if the clock is decreased the range will extend across neighbouring bit widths and become unspecified TIMS AMS1 User Manual 9 QUICK OPERATION GUIDE A Viewing the operation of the DECISION MAKER For example a SEQUENCE GENERATOR and TUNEABLE LOWPASS FILTER as the source of a corrupted digital stream make an ideal demonstration signal 1 Select the appropriate digital waveform being used for the experiment at rotary switch SW1 which is located at the rear of the module 2 Select the correct Z modulation mode to suit your oscilloscope See TECHNICAL DETAILS section on setting up Z modulation 3 Select INT at DECISION switch SW2 near the front of the module 4 Connect the digital signal to IN1 and the bit clock to B CLK input 5 Connect the oscilloscope s EXTERNAL trigger input to the SYNC output of the SEQUENCE GENERATOR 6 Connect the oscilloscope s Z modulation input to Z MODULATION output of the DECISION MAKER module 7 Connect the scope CH1 to IN1 and CH2 to OUT1 8 Turn the DECISION POINT control and observe the movement of the bright marker along the input waveform and see the resultant output waveform Also compare with the original waveform from the SEQUENCE GENERATOR B Viewing EYE DIAGRAMS with the DECISION MAKER For example a SEQUENCE GENERATOR and TUNEABLE LOWP
119. uadrature Utilities Speech Module Multiple Sequences Source CDMA Decoder E SPECIAL APPLICATIONS MODULE LIST Below are listed all the TIMS SPECIAL APPLICATIONS MODULES 100kHz Tx Antenna 100kHz Rx Antenna Utilities Fibre Optics Transmitter Fibre Optics Receiver TIMS AMS1 User Manual 3 BASEBAND CHANNEL FILTERS PULSE SHAPING FILTERS Four switch selectable baseband channels are provided comprising three different filters and one straight through connection Each of the three filters has a stop band frequency of near 4kHz BASEBAND CHANNEL FILTERS CHANNEL SELECT SWITCH IN CHANNEL OUT CHANNEL SELECT INPUT COUPLING oc SWITCH AC ANALOG INPUT OUTPUT IN OUT BLOCK DIAGRAM FRONT PANEL USE Only one channel may be selected and used at a time Note that each of the four channels may be AC or DC coupled by front panel toggle switch CHANNEL CHARACTERISTICS Before using any of these four channels in experiments each channel should be characterised by actual measurement of amplitude and phase responses As a minimum the cut off and stop band frequencies should be measured using the AUDIO OSCILLATOR and TRUE RMS METER modules or an oscilloscope COMPARISONS AMPLITUDE AND PHASE VERSUS FREQUENCY It is useful to compare the amplitude and phase response of each channel with the 7th order elliptic TUNEABLE LOWPASS FILTER module a standard module from of the BASIC MODULE SET Compare aga
120. uence generator is identical to the sequence generators supplied in the MULTIPLE SEQUENCES SOURCE CDMA ENCODER module The generator has two TTL level inputs one TTL level output and one TIMS level bipolar output Inputs CLK is the sequence s external bit clock input The input clock signal s frequency can range from a few hertz to over 1MHz The sequence may be reset by depressing the front panel push button or by applying a TTL level HI at the RS RESET input Outputs The sequence output labeled PN is a TIMS level bipolar signal The SYNC pulse is used to identify one complete repetition of the sequence The TTL level HI pulse at the SYNC output coincides with the first bit of the sequence Sequence Selection 10 switch selectable multiple length sequences of up to 2141 bits are available These are stored in EPROM and are selected via the PCB mounted switch SW1 It is imperative that the CDMA DECODER module and MULTIPLE SEQUENCES SOURCE module both have identical version EPROMs installed when they are used in the same experiment The standard EPROM provided PNSQ1 1 contains sequences of two fixed lengths long and short at the following switch positions SW1 and SW2 SEQUENCE SEQUENCE POSITION LENGTH TYPE 0 214 4 long maximal length 1 2144 long maximal length 2 alt long maximal length 3 214 4 long maximal length 4 27 1 short maximal length 5 27 1 short maximal length 6 214 4 lon
121. uide Setting up the TIMS DSP DB amp TIMS DSP RB EPROM Operation both TIMS DSP DB amp TIMS DSP RB i Plug the EPROMs into the TIMS DSP module with the EPROM labeled HI located in U5 and the EPROM labeled LO located in U6 ii Ensure the MEMORY SELECT JUMPERS are set for EPROM RAM mode A1 A2 A3 amp A4 iii Jumper J1 should be in position L iv Plug the DSP module into the TIMS rack RAM Operation TIMS DSP DB only i Ensure the MEMORY SELECT JUMPERS are set for RAM mode B1 B2 B3 amp B4 ii Ensure that EPROMs are not installed in IC positions U5 amp U6 iii Plug the DSP module into the TIMS rack iv Connect the DSP module s SERIAL LINK to your computer s serial port reserved for communications with the DSP module and down load the decoder program required Seiting up the TIMS AIB i Remove the jumper at J1 NOTE jumper J1 must NOT be connected as BIO mode is required ii Plug the AIB module into the TIMS rack immediately to the right of the DSP module The TIMS DSP and TIMS AIB modules are now ready for operation TIMS AMS1 User Manual 75 QUICK OPERATION GUIDE A Setting up the TCM Encoder Modulator 1 The modules required for the TIMS 4 AM TCM modulator are patched together as illustrated in Figure 1 on the first page of this chapter 2 Select CODE 2 at the front panel of the CONVOLUTIONAL CODE ENCODER module 3 The last step in setting up the TCM modulator is to adjust the amplitu
122. ulators the ADDER module must always be set up first Initially both of the ADDER S gains MUST be set to unity FOR THE ADAPTIVE DELTA MODULATOR A TIMS MULTIPLIER module is inserted at the INTEGRATOR S input the signal to the INTEGRATOR is multiplied by the voltage from the ADAPTIVE CONTROL output Hence providing effective control over the INTEGRATOR S gain TIMS AMS1 User Manual 13 BASIC SPECIFICATIONS INTEGRATOR Input frequency range 400Hz to 10kHz Output integral of the input with inversion Gain user selectable by DIP switch HARD LIMITER Input frequency range 10Hz to gt 500kHz Output TTL level SAMPLER Input TTL level digital signal Digital output TTL level digital signal Analog output bipolar digital signal approx 5V and 5V Clock input lt 1kHz to gt 500kHz Clock selection divides input clock by 1 2 or 4 Adaptive Control Output 2V normal mode approx 4V adaptive mode Adaptive Control Coincidence Condition 000 or 111 adaptive signal is active at the third bit if three successive ONEs or three successive ZEROs have occured TIMS AMS1 User Manual 14 INTEGRATOR OVERVIEW A simple inverting integrator circuit is shown in figure DM 1 figure DM 1 Defining the current flowing through the R and C IR lc therefore Vin R CdVourt dt Over a fixed interval say Ts VouT VINTs RC When this is applied to the DELTA MODULATION UTILITIES module then Vin SAMPLER analog DATA outp
123. ulse Width Modulation which can be used in PWM and along with other TIMS modules in PPM applications BIT CLOCK CLOCK OUTPUT INTEGRATE amp DUMP ey NbUT INTEGRATE amp DUMP DIGITAL DUMP DELAY CONTROL BIT CLOCK DELAYED INPUT BIT CLOCK casi SYE e non tl T eHow INPUT 1 OUTPUT 1 1 alee INPUT 2 OUTPUT 2 I SAMPLING OUTPUT BIT CLOCK READY Weite 7 SAMPLE Am amp HOLD FRONT PANEL CLK w PWM INPUT PWM OUTPUT CLK USE BLOCK DIAGRAM DIGITAL DELAY The variable digital delay accepts a standard TTL level signal at the B CLK input and also outputs a standard TTL level signal at the CLK OUT output Adjusting the DELAY control knob provides a digital phase delay function by varying the time between the positive edge of the signal at the B CLK input with respect to the positive edge of the output signal at CLK OUT Note that the duty cycle of the input signal is not maintained during the digital delay function The output signal at CLK OUT is a fixed pulse of about 10usec width TIMS AMS1 User Manual 67 The DELAY control knob will vary the digital delay time from approximately 10usec to 1 5msec over four user selectable ranges The adjustment range is selected via the PCB mount switch SW3 Refer to the following table for switch settings SW3 2 A SW3 1 B DELAY ranges OFF OFF 10us 100us OFF ON 60us 500us ON OFF 100us 1ms ON ON 150us 1 5ms The timing diagram below illustrates the
124. used to drive the ANTENNA ANTENNA BUFFER AMPLIFIER MAXIMUM RADIATION INPUT BLOCK DIAGRAM LOOP ANTENNA USE POSITIONING The ANTENNA should always be placed on top of the TIMS 301 system unit Ensure that the TIMS 301 s front feet are folded back so the top of the system unit is not sloping Always be aware that the maximum signal radiation is in the direction of the loop s opening perpendicular to the plane of the loop CONNECTION The transmitter antenna system is set up for operation by connecting the ANTENNA s coaxial cable active red plug in to the BUFFER AMPLIFIER output and the shield black plug into the TIMS 301 s green GROUND socket BOTH CONNECTIONS MUST BE MADE FOR CORRECT ANTENNA OPERATION The signal to be broadcast is connected to the BUFFER AMPLIFIER module s input socket Use an oscilloscope to monitor the amplitude of the signal going into the ANTENNA Adjust the the amplitude of the driving signal using the BUFFER AMPLIFIER module s GAIN control The amplitude of the driving signal should be in the range of 4V pk pk to 10V pk pk max Never allow the amplitude to exceed 10V pk pk BASIC SPECIFICATIONS Antenna Type tuned wire wound loop antenna Feed low impedance coaxial cable with 4mm terminals Resonant Frequency approx 100kHz Usable Frequency Range 75kHz to 125kHz TIMS AMS1 User Manual 106 100kHz RX ANTENNA UTILITIES A loop antenna designed for operation in t
125. ust be supplied with the same bit clock CLK iii Frame Synchronisation Two methods are available to indicate frame synchronisation of the TDM PCM data stream the MASTER module s frame synchronisation output FS and an embedded code within the TDM serial data The operation of the MASTER module s frame synchronisation output FS under TDM Mode is exactly the same as described previously under single channel PCM operation As well the frame synchronisation code is embedded within the TDM PCM data exactly as described under individual PCM ENCODER module operation Note that the MASTER will always have a 1 as its LSB frame synchronisation bit and the SLAVE will always have 0 as its LSB frame synchronisation bit in order to facilitate correct de multiplexing by the PCM DECODER modules iv TDM Operation As all three of the PCM ENCODER module s digitising schemes have the same frame length that is 8 bits the two modules operating in TDM mode may have the same or different digitising schemes selected simultaneously For example the MASTER may be sending 7 bit linear digitised data while the SLAVE may be sending 4 bit companded data BASIC SPECIFICATIONS Input Vin 2Vpk DC coupled Bit Clock Input lt 10kHz TTL level Output Signal serial TTL level data stream in offset binary format Output Format 8 bits data including frame synchronisation bit as LSB Digitising Formats 7 bits linear 4 bits linear and 4 bits companded
126. ut TTL Input 1 The decoder s input for TTL level convolutionally encoded serial data OUTPUT SIGNALS Two output signals are provided DECODED DATA the AIB module s TTL Output 2 and data bit clock CLK the AIB module s TTL Output 1 CLK TTL Output 1 The decoded data s bit clock CLK is synchronised and in phase with the decoded data sequence The frequency of the CLK signal is half that of input CODE CLOCK signal DECODED DATA Output TTL Output 2 The data at the output of the decoder is generated by the Viterbi Algorithm as the most likely data sequence to have been transmitted given the received input sequence to the decoder Note that one data bit is generated for every two bits of received encoded sequence OPERATING MODE In the decoding process it is important that the decoder correctly determines the beginning of each codeword in the received sequence This process is referred to as branch word synchronisation When synchronisation is incorrect excessive errors will appear in the decoder s output The CONVOLUTIONAL DECODER as implemented by the DSP modules and software provides two methods of branch word synchronisation The AIB module s three position switch is used to to control branch word synchronisation in the following manner AIB module s DECODER AUTOMATIC MANUAL SWITCH MODE OPERATION OPERATION POSITION upper Automatic Requires TEST Not used CODE as input m
127. ut approximately 5V and 5V Ts the selected sample clock period R INTEGRATOR S resistor value determined by switch SW2 C INTEGRATOR S capacitor fixed at 47nF 5 C2 on the PCB Vout STEP SIZE The value of the INTEGRATOR S resistor is determined by switch SW2 according to figure DM 2 Ril R12 SW2A R13 SW2B OFF ON figure DM 2 where default values are R11 5k6R R12 5k6R R13 1k5R The resistors have a basic tolerance of 1 TIMS AMS1 User Manual 15 QUICK OPERATION GUIDE SIMPLE DELTA MODULATOR 1 Initially use the MASTER SIGNALS module for synchronised message and clock signals This will produce stable scope displays 2 Take an ADDER module and using the scope adjust each input s gain to unity Apply a signal to one input only and adjust the gain so that the output and input amplitudes are equal while leaving the other input not connected Repeat the same procedure for the second input 3 Patch the 2kHz sinewave from the MASTER SIGNALS module to one of the ADDER S inputs Also patch the MASTER SIGNAL S 100kHz TTL output to the SAMPLER S clock input 4 Patch the ADDER S output to the HARD LIMITER S input 5 Patch the HARD LIMITER S output to the SAMPLER S input 6 Patch the SAMPLER S analog output to the INTEGRATOR S input 7 Finally patch the INTEGRATOR S output to the ADDER S second input This completes the simple Delta Modulator When view
128. ut signals 4 AM TCM encoded modulated data which would typically be the output of a noisy 100kHz channel A stolen bit clock whose phase is then aligned with the TCM data stream using the variable DELAY function of the INTEGRATE amp DUMP module A stolen carrier whose phase is then aligned with the incoming TCM carrier modulated signal using the PHASE SHIFTER module TIMS AMS1 User Manual 72 The bit clock alignment adjustment and local carrier phase alignment adjustment is done while observing the outputs of the INTEGRATE amp DUMP module to achieve a nominal 4 level encoded data stream using the following criteria LOCAL CARRIER PHASE ADJUSTMENT Adjust the local carrier s phase such that the amplitude of the multilevel data at the INTEGRATE amp DUMP module s 1 amp D1 output is a nominal 3V peak to peak recall that integrate amp hold mode must be selected for channel 1 amp D1 BIT CLOCK ALIGNMENT Since each TCM symbol is a DC voltage integrating over only one symbol within a bit clock cycle will result in a single ramp within that single bit clock cycle Hence integrating over two symbols within a bit clock cycle will result in the occurrence of two opposing ramps within some bit clock cycles Therefore the INTEGRATE amp DUMP module s second channel 1 amp D2 may be used to assist in achieving correct alignment between the bit clock and the data stream Make an additional connection from the output of the MU
129. ut to both the FREQUENCY COUNTER and one of the MULTIPLIER s input sockets iv Patch the MULTIPLIER s output to the SPECTRUM UTILITIES module s input TIMS AMS1 User Manual 36 The spectrum analyser is now complete apply the signal to be investigated to the MULTIPLIER s other input SPECTRUM ANALYSER OPERATION v Adjust the VCO module s frequency control fo to the expected vicinity of the frequency of interest Slowly vary fo until you notice the analog panel meter s pointer starting to oscillate vi Now slowly adjust the VCO s output frequency by varying the VARIABLE DC VOLTAGE until the analog panel meter pointer oscillates very slowly Record the peak reading of the panel meter and the FREQUENCY COUNTER s display vii Repeat the above two steps v and vi if varying the VARIABLE DC VOLTAGE does not adjust the VCO to the frequency of interest or if other spectral components need to be determined When searching for low level spectral components the precise x1 x10 sensitivity switch will assist in increasing meter sensitivity without disturbing the calibration setting BASIC SPECIFICATIONS Input Voltage Range 10mV to 2V continuously variable Sensitivity Switch x1 x10 Input Frequency Range DC to lt 30Hz Indicator centre zero analog panel meter with linear scale Output filtered scaled and buffered meter movement signal Operating Modes NORMAL PEAK HOLD with push button RESET TIMS AMS1 User Manual
130. uts from each encoder in TEST mode CODE 1 TEST Mode Output Waveforms DATA IN B CLK DATA OUT CODE 2 TEST Mode Output Waveforms DATA IN B CLK DATA OUT s i denotes repetition of the output sequence TIMS AMS1 User Manual 59 QUICK OPERATION GUIDE A Setting up and Familiarisation with Convolutional Encoders 1 Select the front panel mode switch to TEST CODE amp the front panel code switch to CODE 1 2 Plug the CONVOLUTIONAL ENCODER module into the TIMS rack 3 Patch the TIMS MASTER SIGNALS module s 8 33kKHz SAMPLE CLOCK to the CONVOLUTIONAL ENCODER module s M CLK input 4 Depress the mode switch momentarily to RESET 5 Patch the scope s CH1 to the encoder module s DATA output and the scope s CH2 to the bit clock output B CLK Observe the relationship between the bit clock and the encoded output data 6 Familiarise yourself with each of the encoder module s other outputs by moving the CH2 lead between outputs and compare with the timing diagrams given in the TECHNICAL DETAILS section of this chapter 7 Select CODE 2 and repeat the above steps 5 to 6 B Normal Operation of the Convolutional Encoder
131. utton Release the ENCODER S RESET push button BASIC SPECIFICATIONS Inputs B CLK TTL level bit clock synchronised to the input data fmax gt 100kHz Encoded signal inputs see ENCODER module section of this manual for definitions Outputs DATA decoded TTL level data STROBE TTL level signal TIMS AMS1 User Manual 31 NOISE GENERATOR A broadband noise source with a 12 step output amplitude attenuator NOISE GENERATOR b S w OUTPUT FRONT PANEL BLOCK DIAGRAM USE The module requires no input or control signals The output noise level can be varied in discrete steps of 2dB Minimum noise level is at OdB and maximum noise level is at 22dB If required the characteristics of the output noise signal can be altered by filtering using any of the TIMS filter modules or attenuated or amplified using the TIMS BUFFER AMPLIFIER or ADDER modules BASIC SPECIFICATIONS Bandwidth 1Hz to lt 500kHz Maximum level approx 1Vrms at 22dB position Attenuator steps 12 steps 0dB to 22dB 2dB per step Attenuator accuracy lt 0 25dB to any two adjacent steps 0 1dB typically lt 0 35dB between any two steps TIMS AMS1 User Manual 32 WIDEBAND TRUE RMS VOLT METER A wideband true RMS volt meter with large LED digital display and a buffered DC output WIDEBAND TRUE RMS METER RANGE SELECT INPUT COUPLING IN SWITCH SWITCH BUFFERED OUTPUT SYSTEM GROUND
132. vel NOTE As both convolutional codes CODE 1 and CODE 2 are rate R 1 2 the encoder will output two encoded bits for each input data bit The B CLK output provides a synchronised and in phase bit clock for DATA and OUT2 signals Parallel Output Each branch of the selected convolutional encoder refer to diagrams of encoder structure is also output separately providing the output encoded sequence bits in parallel The parallel outputs are TTL level and labeled BIT 1 and BIT 0 Note that the parallel output bits are delayed in phase with respect to the serial output bits by half a cycle of the bit clock B CLK TIMS AMS1 User Manual 55 The two parallel bits are also presented to a 2 bit digital to analog converter which outputs a 4 level bipolar signal at OUT4 Output bits to output voltage mapping in indicated below BIT 1 BIT 0 OUT4 1 1 1 5V 1 0 0 5V 0 1 0 5V 0 0 1 5V The S CLK output may be used as a synchronised though out of phase bit clock for BIT 1 BIT 0 and OUT4 signals B CLK and S CLK Output Clock Signals S CLK must be used as the bit clock for the module providing the digital data sequence normally either the SEQUENCE GENERATOR module or the PCM ENCODER module B CLK is a bit clock that is in phase and synchronised with the serial encoded output data The frequency relationship between the input and output clock signals is as follows B CLK M CLK 4 S CLK M CLK 8 and
133. verify that the 4 AM TCM symbols have 4 voltage levels Adjust the BUFFER AMPLIFIERS module s variable gain control such that the span of the whole symbol set is 3V peak to peak When correctly operating and adjusted the 4 AM TCM modulator outputs only 4 data levels at approximately 1 5V 0 5V 0 5V and 1 5V and at a symbol rate of 1kHz USE 4 AM TCM DEMODULATOR MODULES REQUIRED i Matched filter implementation requires INTEGRATE amp DUMP module with integrate amp hold mode selected on channel 1 amp D1 MULTIPLIER module PHASE SHIFTER module ii Soft decision Viterbi decoder implementation requires The TIMS Digital Signal Processing module set either the TIMS 320 DB development board and the TIMS AIB analog interface board or the TIMS 320 RB run board and the TIMS AIB analog interface board SOFTWARE FIRMWARE REQUIRED The TIMS TCM VITERBI DECODER program is required which is available in both EPROM and floppy disk format SIGNAL DESCRIPTIONS amp SETTING UP Before commencing with the TCM demodulator set up the user must be familiar with the setting up and operation of the INTEGRATE amp DUMP module Please refer to the User Manual chapter describing the INTEGRATE amp DUMP module The modules required for the TIMS 4 AM TCM demodulator are patched together as illustrated in Figure 2 on the previous page i Matched filter implementation signals The TIMS implementation of the matched filter requires 3 inp

TIMS ADVANCED MODULES and TIMS SPECIAL APPLICATIONS

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