DMA120, DMA121 Digital Modulation Analyzers
Contents
1. sion figure of merit mea surement MER provides a much earlier indication of transmission impairments MER indicates the ratio of average total signal power in the ideal constellation to average error power in the constellation as received by the DMA120 Series The mea surement includes error power due to any impair ment If the only impairment in the test channel spectrum is noise MER is equal to sig nal to noise Technicians will feel familiarity with MER because results are expressed in dB similar to analog trans mission carrier to noise or signal to noise measure ments The DMA120 Series measurement screen see Figure 1 shows MER vs time providing trend infor mation Error Vector Magnitude EVM EVM isan alternative figure of merit measure ment It has been a perfor mance measurement for digi tal communication systems in the past and provides a means of system comparabil ity for some engineers The same distortion elements are measured as in MER How ever the calculation of error is different and is expressed as a percentage of the maximum voltage in the con stell ation at sampling times as received by the DMA120 Series Estimated Noise Margin The legacy of rf broadband system maintenance has been based on measurements in the fre quency domain Technicians are conditioned to thinking of system headroom in terms of dB carrier to noise or dBc for CSO CTB or cross modu2. lation Estimated Noise M ar gin indicates the headroom for digital channels and results are reported in dB similar to legacy analog mea surements Essentially simu lated gaussian noise is added to the input signal until a critical pre FEC BER of 10 4 is measured The added sim ulated noise equals the Esti mated Noise Margin which answers the question how many dB until subscribers are receiving impaired digital services Bit Error Rate BER before Reed Solomon R S decod ing BER is an important mea surement to document sys tem performance The typical system operating goal is to achieve a BER of 10 9 Ser vice impairment will typi cally be observed at bit error rates greater than 10 4 The BER measurement is the aver age ratio of bit errors to total bits received in a specified time period The DMA120 Series BER measurement may be set for any period from 1 to 60 minutes Results from successive periods can be compared to show a 24 period trend 30 20 10 ia 10 20 30 40 50 121 00 23 ma 101 00 Center 106 00 111 00 Start Stop Attenuation Automatic 22341999 1 35 10 111 00 1146 00 101 00 ten 121 00 CH 99 Recall 2047371339 i 7 42 05 g Lack CH 97 Continuous Sampleil2il EUM lt i X t MER gt 35 0 dB pass BER 7 7E 07 Before R S Figure 4 Constellation display mode Estimated BER after R S decoding BER a
3. zoom modes a constellation quadrant view and asingle constellation box can be selected to closely examine the distribution of symbol landings Decision bound aries are displayed along with adjacent boxes to make it easy to see the symbol landing patterns see Figure 5 page 3 T TET 34 1998 m ol p P iy au GEERTEN Lock CH i07 oe cx I wh a i 4 aaa RS Sample 101 ie RH a EUM 3 0 4 MER 26 7 dB i FAIL 7 ae BER 5 8E 06 F e 7 oo i Figure 5 Constellation Box Evaluate mode Adaptive Equalizer Display Mode This display indicates linear impairments such as poor frequency response and reflections Tap values show how hard the equalizer is working to compensate for impairments The display includes a bar graph which compares the values of the different taps against a DVB template Bars approaching or exceeding the template value indicate that there is noticeable system impair ment detected at the test point New Measurement Technology That s Easy to Use Using the DMA120 Series is easy Most measurement functions are no more than two menus deep Navigation through menus is straight for ward and there s aMENU key on the front panel that instantly gets the user to the instrument s Main Menu screen Universal set up page 4 parameters are part of a Set Up screen Measurement spe cific set up parameters are part of the individual mea
4. Constellation Spectrum and Equalization Display Modes Most Measurements Require Only Two Keystrokes Pass fail Indication Reduces Training Requirements for Technicians New to Digital Signal Measurements PC Card PCMCIA Slot for Easy Memory Expansion Small and Light Weight Easy change Battery 4Min 3Min 2Min LMin MER dB 32 5 Estim Noise Margin tdB 5 6 22 3 1999 1 32 46 Status Lock Recall PASS Figure 1 MER and Estimated Noise Margin screen Before R S Measured After R S Estimated O 0E 00 Rate F 9E 04 Current Previous Current Previous SES Average Rate g LE 04 2E 04 L 4E 08 2 1E 08 Error Sec 21 63 Unavailable Sor l a Period Remain Min Sec 20 i q Set C1 60 mina 207371999 6 54 16 Status Lock Graph Figure 2 BER screen Qualify System Performance The built in digital demodu lator makes possible in ser vice measurements of e Modulation Error Ratio MER e Error Vector Magnitude EVM e Estimated Noise Margin BER before Reed Solomon R S decoder e Estimated BER after R S decoder with system avail ability statistics page 2 Modulation Error Ratio MER ETSI ETR290 indi cates that MER is the best overall figure of merit mea surement to determine QAM signal quality Although bit error rate BER has been widely addressed as an important digital transmis
5. include e Print screen Any measure ment or display mode screen can be directly printed via RS 232 inter face Up to 30 constellations or 100 other measurement results can be stored in internal memory with real time clock date stamp measurement site name operator name and ambi ent temperature User changeable input adapter type F or BNC optional accessory PC Card PCMCIA input for 2 and 20 Megabyte memory cards to store additional measurement results and or system chan nel tables User changeable NiMH battery to extend the oper ating day battery capacity indicator user selectable automatic power down DMA 120 Series Characteristics NOTE All specifications apply across the operating temperature range 5 to 40 C unless otherwise stated All values refer to measurement after 25 minute warmup All power measurements referenced to 75 Q impedance RECEIVER Frequency Range channel center frequency DMA120 54 to 860 MHz DMA121 50 to 866 MHz Resolution Bandwidths typical DMA120 135 kHz 6 MHz DMA121 135 kHz 8 MHz Input Impedance 75 Q nominal Maximum Input RF Power 120 dBuV 60 dBmV AC Volts 90 V peak Distortion free Dynamic Range gt 40 dB Sensitivity lt 20 dByV 40 dBmV DISPLAY MODES Spectrum Displayed Level average power of 64QAM signal at 6 875 Msymb s Minimum 40 dByV 20 dBmV Maximum 100 dBuV 40 dBmV Attenuation Steps
6. surement screens Digital transmission is new to most cable TV system techni cians and so are measure ments to verify performance Technicians may not under stand exactly how these mea surements function or how to interpret measurement results However measure ments are still required to continue system installation and maintenance activities The DMA120 Series helps technicians to continue work ing by providing measure ment pass fail indicators The system engineer or chief tech nician can determine the measurement result thresh old values This enables the technician to continue work ing if measurements are pass ing or follow an Engineering directive if failures are encountered Pass fail indica tors are available for MER RF Signal Level Adjacent Channel Level Channel Power to Noise Severely Errored Seconds BER mode Status indicators also help clarify measurement condi tions the DMA120 Series notes if it s locking to the incoming QAM signal and also if it s locking to the R S decoder output The actual received symbol rate is also reported Operating Convenience The DMA 120 Series uses a moisture and dust proof keypad It uses a high resol u tion LCD display with back light Contrast controls are conveniently located on the front panel The DMA120 Series includes many capabilities designed to simplify the job of digital plant installation and mainte nance Ancillary enhance ments
7. 5 dB typical Attenuation Range 35 dB typical Vertical Scale 10 dB div 10 to 90 dBuV 50 to 30 dBmV 100 to 20 dBm Span Settings 2 to 824 MHz fixed to 135 kHz RBW Flatness 1 dB Constellation Sizes 64QAM 256QAM Evaluation Full constellation quadrant single point box Adaptive Equalizer Number of Taps DMA120 8 feed forward 8 feed back DMA121 8 feed forward 24 feed back Scale 10 to 40 dBc Mask DVB MEASUREMENT MODES Signal Level Channel Bandwidth DMA120 6 MHz DMA121 8 MHz Level channel average power Minimum 40 dBuV 20 dBmV Maximum 100 dBuV 40 dBmV Accuracy 64QAM 1 5 dB referenced to 25 C 256QAM 1 8 dB referenced to 25 C Reference Units selectable dBuV dBmV dBm dBpW Pass Fail Indication User adjustable threshold In service Measurement Channel Power to Noise Channel Bandwidth DMA120 6 MHz DMA121 8 MHz Maximum Ratio 40 dB Accuracy 2 1 dB Pass Fail Indication User adjustable threshold In service Measurement Noise measure ment frequency out of channel Adjacent Channel Level Difference Amplitude Range DMA120 10 to 25 dB DMA121 15 to 25 dB Accuracy 2 1 dB referenced to 25 C Display Vertical Scale 40 to 100 dBuV 20 to 40 dBmV 65 to 5 dBm 25 to 85 dBpW Pass Fail Indication User adjustable threshold In service Measurement Modulation Error Ratio MER Range 64QAM 22 to 35 dB 256QAM DM
8. A120 28 to 35 dB 256QAM DMA121 30 to 35 dB Accuracy 1 5 dB at 65 dBuV 5 dBmV referenced to 25 C Pass Fail Indication User adjustable threshold In service Measurement Error Vector Magnitude EVM Range 64QAM 1 2 to 4 1 256QAM 1 1 to 1 9 Accuracy 0 4 over 1 2 to 2 0 range 0 8 over 2 1 to 4 1 range at 65 dBuV 5 dBmV In service Measurement Average Bit Error Rate BER Before R S Decoding Range 64QAM 10 4 to 10 9 256QAM DMA120 10 to 10 8 256QAM DMA121 10 4 to 10 8 User selectable Time Period 1 to 60 minutes Number of Periods Comparable 24 In service Measurement Estimated Average Bit Error Rate BER After R S decoding User selectable Time Period 1 to 60 minutes Number Periods Comparable 24 In service Measurement System Availability Statistics User selectable Time Period 1 to 60 minutes Errored Seconds Severely Errored Seconds Pass Fail indication User settable threshold Unavailable Time Severely Disturbed Period In service Measurement Estimated Noise Margin Range DMA120 64QAM 1 to 12 dB 256QAM 2 to 7 dB DMA121 64QAM 1 to 10 dB 256QAM 3 to 5 cB Accuracy 1 5 dB at 65 dBuV 5 dBmV Symbol Rate Range DMA120 5 057 to 5 360 Msymb s DMA121 5 000 to 6 956 Msymb s page 5 Temperature Operating 5 to 40 C Altitude Operating Up to 4 600 m 15 000 ft Non operating Up to 15 000 m 50 000 ft Qualified
9. DMA120 DMA121 Digital Modulation Tektronix Analyzers Affordable portable ready for cable system technicians digital channel 64 and 256QAM transmission performance verification measurements The DMA 120 Series Digital Modulation Analyzers pro vide answers to nagging ques tions about how to test and verify performance of your digital plant Quantification of digital transmission perfor mance at any pointin your system will greatly enhance technical management and decision making The DMA120 provides analysis of ITU T 83 Annex B 64 and 256QAM and the DMA121 verifies 64 and 256QAM for matted per DVB C Copyright 1999 Tektronix Inc All rights reserved The DMA120 Series provides the intelligence cable TV technicians need to effi ciently install and maintain HFC distribution plant using 64 or 256QAM transmission Measurement results provide a clear picture of system per formance minimizing the need to re visit an installa tion site or make additional service calls The DMA 120 Series field tools are housed in arugged weather resistant package and are powered by an easy to change NiMh bat tery Standard accessories include a protective soft case mains power supply and user s manual 64 and 256QAM Analysis In service Digital Channel Performance Verification Measurements at an Affordable Price Measurements Compliant with DVB ETSI Standard ETR290 Troubleshooting Aided by
10. Per The Following Standards U S A FCC CFR 47 Part 15 Subpart B Class A Australian EMC Framework AS NZS 2064 1 2 EU EMC Directive 89 336EEC EN 55011 Class A IEC 1000 4 2 ESD immunity IEC 801 3 RF field immunity IEC 1000 4 4 EFT burst immunity DMA 120 ENVIRONMENTAL Series Characteristics Continued EMC COMPLIANCE POWER page 6 DC Input Range 12 V 2 A Battery Run Time gt 2 5 hours typical Battery Charge Time instrument off 4 hours typical PHYSICAL CHARACTERISTICS Dimensions cm in Height 32 12 5 Width 17 6 75 Depth 6 2 25 Weight kg lb Net 2 1 4 6 WARRANTY One year parts and labor OTHER Communication Interface RS 232 speed 9600 to 115 200 baud Channel Tables User defined tables in standard memory Additional stored in PC Card PCMCIA memory cards DMA 120 Ordering Information DM A120 Digital Modulation Analyzer for ITU T J83 Annex B 64QAM DMA121 Digital Modulation Analyzer for DVB C 64QAM Both Include User s Manual Reference Card Padded Carrying Case 120 VAC North American Power Pack with DMA120 220 VAC Euro Universal Power Pack with DMA121 Preci sion Female Female Type F Adapter Vehicle Power Adapter Channel Table Loader Soft ware with Manual RJ45 to 9 pin Adapter RJ45 Cable DM A120 Series Options Option C3 Three years calibration services Option C5 Five years calibration services O
11. al Channel Average Power RF signal level mea surement is made by integrat ingall the channel power through a channel bandwidth IF filter A user settabl e offset is available to accommodate probe loss The Signal Level measurement screen plots signal levels vs time provid ing a convenient display from which to make gain or attenu ation adjustments or judge other variables that can impact signal level Adjacent Channel Levels Potential interference to adjacent channels can be verified using this measure ment The Adjacent Channel Levels display compares the test channel average power to the average power in each of the two higher and two lower adjacent channels The mea surement results screen includes a bar graph compar ing the test channel and adja cent channels power This measurement may be used to check flatness across five channels or verify spectral purity of aQAM modulator Spectrum Display Mode The channel or system spectrum can be viewed in this mode channel symmetry and flat ness and relative signal lev els can be visually confirmed see Figure 3 Constellation Display Mode Digital modulation quality can be visually esti mated by viewing the con stellation of the transmitted signal See Figure 4 Distri bution impairments can be identified including noise and coherent interferers or modulator impairments such as I Q imbalance or quadra ture error The DMA120 Series also includes two
12. ean 52 5 666 6333 The Netherlands 31 23 56 95555 Norway 47 22 07 07 00 People s Republic of China 86 10 6235 1230 Republic of Korea 82 2 528 5299 South Africa 27 11 651 5222 Spain amp Portugal 34 91 372 6000 Sweden 46 8 477 65 00 Switzerland 41 41 729 36 40 Taiwan 886 2 2722 9622 United Kingdom amp Eire 44 0 1628 403300 USA 1 800 426 2200 From other areas contact Tektronix Inc Export Sales P O Box 500 M S 50 255 Beaverton Oregon 97077 0001 USA 1 503 627 6877 gg SO 9001 amp C Copyright 1999 Tektronix Inc All rights reserved Tektronix products are covered by U S and foreign patents issued and pending Information in this publication supersedes that in all previously published material Specification and price change privileges reserved TEKTRONIX and TEK are registered trademarks of Tektronix Inc All other trade names referenced are the service marks trademarks or registered trademarks of their respective companies Tektronix 5 99 HB XBS 21W 12235 2
13. fter R S decoding represents the ser vice level that the cable sys tem is providing to the sub scriber s TV receiver or com puter The R S decoder is typically able to correct errors up to an input BER of approximately 10 4 Beyond this value uncorrected errors pass through the decoder this is the value reported by Estimated BER see Figure 2 System availability statistics are also reported by the DMA 120 Series including e Errored seconds number of seconds that include an errored block fe pe ete ale eh Re ee e Severely errored seconds one second periods with greater than specified num ber of errored blocks e Severely disturbed periods duration of sync loss e System unavailability time time period containing at least 10 consecutive severely errored seconds System availability statistics are very useful for tracking intermittent impairments that may not be observable based on MER or average BER mea surements Maintain and Troubleshoot Your Digital Video Plant When performance quality measurements indicate trans mission problems the DMA 120 Series can provide assistance to find out what s wrong Additional measure ments and display modes that can help the technician include e Channel Average Power Signal Level e Adjacent Channel Levels e Spectrum Display Mode e Constellation Display Mode with zoom capability e Adaptive Equalizer Display Mode Digit
14. ption R3 Three years post warranty repair protection Option R5 Five years post warranty repair protection AC Adapter Options Option A0 North American 115 V 60 Hz standard with DMA120 Option A1 Euro Universal 220 V 50 Hz standard with DMA121 Option A2 U K 240 VAC 50 Hz Option A3 Australian 240 V 50 Hz DM A120 Series Recommended Accessories Type F to BNC Input Adapter 103 0310 00 Additional Battery DMABAT External Battery Charger for DMABAT DMACHG specify power cord Option A2 or A3 as applicable Thermal Printer DMAPRN Includes Five Rolls Paper Battery AC Adapter Select one of following AC Adapter options Option AO North American 115 V 60 Hz Option A1 Euro Universal 220 V 50 Hz page 7 For further information contact Tektronix Worldwide Web for the most up to date product information visit our web site at www tektronix com ASEAN Countries 65 356 3900 Australia amp New Zealand 61 2 9888 0100 Austria Central Eastern Europe Greece Turkey Malta amp Cyprus 43 2236 8092 0 Belgium 32 2 715 89 70 Brazil and South America 55 11 3741 8360 Canada 1 800 661 5625 Denmark 45 44 850 700 Finland 358 9 4783 400 France amp North Africa 33 1 69 86 81 81 Germany 49 221 94 77 400 Hong Kong 852 2585 6688 India 91 80 2275577 Italy 39 2 25086 501 Japan Sony Tektronix Corporation 81 3 3448 3111 Mexico Central America amp Caribb
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