BODE100 Quickstart for Spectrum Analysis
Contents
1. back to an optimized diagram OUTPUT a Config with OUTPUT internally connected to CH b Resulting result_vector Fig 2 1 Gain Phase measurement result vector Amplitude exp j Phase Look on which side of the output resistor the reference channel CH is internally connected to OUTPUT This delivers correct results for V CH2 V CHI with a 50Q load impedance connected to OUTPUT As illustrated in the figure below We will now figure out what happens when the 50Q load impedance is removed as shown in the bottom figure below Use the and fooler buttons to start and stop the following measurements A BNC 50Q termination resistor is used as external load to OUTPUT Which amplification do you measure in the OUTPUT CH1 CH Gain Phase mode dB and factor O OdB Factor 1 Remove the 50 resistor and measure again as shown in the figure below Which amplification do you measure for this short circuit dB and factor OUTPUT CH1 CH2 Q 6dB Factor 2 It is seen that the measurement delivers wrong results when the load impedance at OUTPUT is not exactly 50Q There are two ways to get accurate results Using CH7 and calibration M Schubert BODE100 Quickstart for Spectrum Analyis Regensburg Univ of Appl Sciences 2 2 Using Reference CH1 for Accurate Measurements Contiguration Recea B aridooadih 1 kHz DUT delay nOD a 4 Fy gc im i pense LE 5 DE rm Right click in the diagram to op2. HOCHSCHULE REGENSBURG UNIVERSITY OF APPLIED SCIENCES BODE100 Quickstart for Spectrum Analysis Prof Dr Martin J W Schubert Electronics Laboratory Regensburg University of Applied Sciences Regensburg M Schubert BODE100 Quickstart for Spectrum Analyis Regensburg Univ of Appl Sciences Abstract A short introduction is given how to measure a Bode diagram using the Bodel00 Vector Network Analyzer 1 2 and the respective software the Bode 100 analyzer Suite 3 Working through this is a precondition for several practical courses of the laboratory System Concepts PSK 1 Introduction This document 1s available at the author s homepage 4 for different laboratories using the Bode 100 vector network analyzer Opposite to simulation we do not have things like 1deal sources or probes in the real world The test instrumentation is circuitry too The most important and complex test instrument in this lab is the Bode 100 vector network analyzer Documentation can be obtained from the Omicron Lab homepage 1 2 submenu Manual pdf files User Manual and Manual Extension Unwrapped Phase 2 2 Getting Started with the Bode 100 Network Analyzer Fig 2 Bode 100 front view Q OF ate nm T o Bode 100 a OMICRON o a OUTPUT CH 1INPUT CH 2 INPUT Switch on the power supply for both Bode 100 and the connected computer and start the Bode Analyzer Suite software While starting it will perform an initial cali
3. bration The software has recognized the hardware when in the lower right corner of the window the serial number of the Bode 100 hardware appears on green background 2 1 Gain Phase Mode With Default Calibration Click the toolbar button Pil to switch to the Gain Phase mode Alternatively you can select Measurement Gain Phase from the Bode Analyzer Suite s menu bar Settings can be saved using File Save As For more details on this mode can see chapter 3 of the User Manual The Bode 100 delivers a sinusoidal voltage signal at OUTPUT measures the voltages at inputs CH1 CH2 and delivers the voltage ratio V CH2 V CHI as result vector Amplitude exp Phase Consider Fig 2 1 a This 1s the default configuration To liberate the user from an external connection between OUTPUT and CHI this connection is made internally However this internal connection is intended for 50 0 measurement engineering assuming a 50 load impedance connected from OUTPUT to ground M Schubert BODE100 Quickstart for Spectrum Analyis Regensburg Univ of Appl Sciences Configuration im ri on 4 ri in 4 i U a E i hi S maom Hant A T om DUI delay ES prune lotos ex Tua Axes Wescure ment 4 J ei My cates alar J U5 m OM a m Right click in the diagram to open the e di Ix shortcut menu Use the shortcut menu e to optimize the diagram select the grid and zoom in the diagram After having zoomed in click Optimize to get
4. en the shortcut menu Use the shortcut menu to optimize the diagram select the grid and zoom in the diagram After having zoomed in click Optimize to get back to an optimized diagram LU TPUT a Config with OUTPUT not internally connected to CH b Vector V CH2 V CH1 Fig 2 2 Gain Phase measurement Vector V CH2 V CHI Amplitude exp j Phase Images taken from Bode 100 User Manual 2 Click the Device Configuration toolbar button or select Configuration Device Configuration from the Bode Analyzer Suite s menu bar or to get into the configuration menu Click on the switch circled red in Fig 2 2 to get the illustrated setting of the switch The connection between OUTPUT and reference input CH has now to be made externally Note to which side of the output resistor the reference channel CH is connected now The measurement will always be correct independently of the load resistor Use the setup of Fig 2 2 with a source frequency 1K Hz to try the two situations below Which amplification do you measure for this short circuit dB and factor OUTPUT CH1 CH2 OdB Factor 1 Which amplification do you measure now dB and factor CH1 CH2 OdB Factor 1 This kind of measurement is always correct but a more uncomfortable due to the required additional cable connected to the reference channel CH1 M Schubert BODE100 Quickstart for Spectrum Analyis Regensburg Univ of Appl Sciences 2 3 User Calibration f
5. est measurements with large bandwidth before doing final accurate measurement with low bandwidth Sweep settings Set frequency sweep See Figure 5 2 Sweep settings on page 44 Cursor settings Set cursors and view measurement results See Figure 5 3 Cursor settings on page 44 Trace settings Define measurement format and display options see Figure 5 4 Trace settings on page 45 OMIKRON Lab Bode Anabyzer Sulte p ISI Ie Fla Mesma jon guruins Calibration Tooke Hag id d mole it a Ras dA User Celi son on Er oie Calibration Freguericy Tis 1 47 20 18 200 MHz v5 Lucr d 11 241855 MHz Trace TATI com MEMINI hes namo Can Stai Frequency 35350 MHz Shop Frecguenp 11 457 MHz E Dios Cerke Freauencg 18 TOO MHz Firmal Spar 1 SUE MH pode mns Humbe af Pans d En Canfgur sion Hess gerer Lem Digis C Aferualr CHI 20 8 B p s ZU L Foraj Magid a ln Ameraser CH2 Ae T r rmm 24 TAB amp I r 44 f ferara fended kHz T1 i Ymn 41 65 Laden Momo Hdestuimenent Figlererice Fiecetance bz Wa WE Ws Wea TR biagi Reala ction Diagram setup See Figure 5 5 Diagram setup on page 46 Export traces data Expor traces as CSV file See 32 Exporing Measurement Data on page 99 Note Only window areas specific for the Frequency Sweep mode are explained For window areas common to other measurement modes see Figure 3 1 Gain Phase mode
6. et a measured result very similar to the measurement in Fig 3 1 b Bode 100 o 9 OUTPUT CH1 CH2 Fig 3 2 a Setup b Uncalibrated measurement Perform a User Calibration with the setup of Fig 3 2 After this Er calibration the setup 3 2 delivers a 2i Odb 0 measurement With this calibration we measure the setup of Fig 3 l a again and get the result shown in Fig 3 3 0000008 09 0m 9 9m m ow Fig 3 3 Measured result for the OpAmp circuit after calibration M Schubert BODE100 Quickstart for Spectrum Analyis Regensburg Univ of Appl Sciences 4 References 1 Available http www omicron lab com 2 Bode 100 User Manual available http www omicron lab com manuals pdf html 3 Bode 100 Network Analyzer Suite available http www omicron lab com downloads html 4 Homepage of M Schubert Regensburg University of Applied Sciences Available http homepages fh regensburg de scm39115 Offered Education Courses and Labs Common Stuff
7. nd CH2 contain a 24 bit AX ADC delivering fs 5 50 Ksps Kilo samples per second Experts only The Main clock rate is fsin 12 8 MHz Consequently the oversampling rate is OSR f i f 47256 To take advantage of the ADC s 24 bit 1 resolution input amplitudes must be adjusted as large as possible blue curve in the figure on the right hand side but not overloaded red curve Overloaded amplitudes introduce large errors by clipping while too small amplitudes loose accuracy by not using the most significant bits of the ADC black curve To optimize the measure ment the user can adjust the sources OUTPUT ampli tude using Level and the attenuation switches for the inputs CH and CH2 The attenuators affect the measured accuracy but not its displayed amplitude For this lab Externally connect OUTPUT an CHI Prefer a source frequency of 1KHz and a receiver bandwidth of 100Hz Source 1 Source Frequency Configuration Attenuator CH2 Receiver Bandwidth Set the output source generator frequency 12 000 MHz set the output source 0 00 dBm generator level Select the channel 1 20 dB input attenuation Select the channel 2 20 dB input attenuation Select the receiver 1 kHz F bandwidth Hint A higher receiver bandwidth allows faster measurements a lower receiver On the bottom right side of bandwidth increases the measurement accuracy the measuremen
8. or Accurate Measurements Without CH1 User Calibration UT LII IR CS OUTPUT CH1 CH2 o O Q Gan Phase Replace DUT bp thin cable dtanaaid precs Start fo parom Lababan BS dwanred EET ES EIE TANAME ETE BE Ok Cancel Help Fig 2 3 Setup for User Calibration with default configuration Figs b c taken from 2 Return to the default configuration shown in Fig 2 1 and connect OUPUT with CH2 as illustrated above Set the source frequency in the Gain Phase menu to 1000 Hz We should now measure 6dB amplification again Select Calibration User Calibration from the Bode Analyzer Suite s menu bar to get into the calibration menu Then select Throu Start Close the Calibration menu with OK and measure again What amplification do you measure for this short circuit now Change the source frequency supplied to OUTPUT from 1000 Hz to 1001 Hz Look at the measurement and look at the calibration menu Is the last calibration still valid No measured result jumps from 0 to 84dB Calibration of the Bode 100 performs a measurement which will be the OdB 0 reference for subsequent measurements New settings require new calibration When several setup changes are required it is easiest to connect OUTPUT and CHI externally and use the default calibration M Schubert BODE100 Quickstart for Spectrum Analyis Regensburg Univ of Appl Sciences 2 4 Optimizing the Measurement Both CH1 a
9. t window next to the Bode 100 s serial number there are amplitude Overload indicators for the channel 1 and channel 2 inputs If you see a red bar increase indicators Their green bar the attenuation of the respective channel or reduce the source level to prevent the overload should be as long as possible but it should not become red indicating ADC overload Figures taken from 2 EEXUED serial number of the Bode 100 Lowering the receiver s bandwidth improves the results on the cost of longer measurement times which can be estimated to be larger than or equal 1 bandwidth M Schubert BODE100 Quickstart for Spectrum Analyis Regensburg Univ of Appl Sciences 2 5 Frequency Sweep Mode Click toolbar button XS to switch to the Frequency Sweep mode Alternatively you can select Measurement Frequency Sweep from the Bode Analyzer Suite s menu bar The frequency sweep mode is documented in chapter 5 of the User Manual A frequency sweep is an assembly of several gain phase measurements The result can be presented as Bode plot as shown on the right hand side Anything we said about configuration and calibra tion for the gain phase mode holds true for the frequency sweep mode also Source level and receiver attenuations have to be set such that the maximum amplitude is just below overload Observe the input channel overload indicators on the lower right hand side of the window carefully Perform t
10. window on page 17 and Figure 4 1 Impedance Reflection mode window on page 33 Figure taken from 2 Check configuration Setup according to Fig 2 2 external connection OUTPUT CHI Select the following Sweep Mode settings Savable using File Save As Start Frequency 100 Hz Stop Frequency 1 MHz Sweep Mode Log Number of Points 201 Receiver Bandwidth 100 Hz Optimize OUTPUT Level and Attenuators E g OUTPUT Level OdB Attenuator CH1 and CH2 20dB Shorten OUTPUT with CH1 and CH2 You should measure OdB over all frequencies Buttons gt Pls and lare available to start a continuously repeated sweep a single sweep and to stop the measurement respectively Measure the short circuit of the cable Get OdB M Schubert BODE100 Quickstart for Spectrum Analyis Regensburg Univ of Appl Sciences 3 Calibration Removing Coupling Capacitor Effects This sub chapter illustrates how calibration can remove side effects from measuring the device under test DUT We configure Bode 100 as illustrated in Fig 2 2 with CHI as external reference and connect it to OUTPUT For a frequency sweep from 1Hz 1KHz of the OpAmp circuit shown in Fig 3 1 a we expect a line very close to OdB but we get the measurement illustrated in Fig 3 1 b TR1 dD E Bode 100 c OUTPUT CH1 CH2 Fig 3 1 a Setup b Uncalibrated measurement To fix the problem we measure the circuit illustrated in Fig 3 2 a and g
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