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Entry  Fri Nov 1 17:54:47 2019, anchal, DailyProgress, FSS, FSS Diagnostics - RFPD RF Ouput under inspection NFSS_RFPD_Output_Oscilloscope.pdfSFSS_RFPD_Output_Oscilloscope.pdfNFSS_RFPD_RF_OUT_COUPLED.pdfSFSS_RFPD_RF_OUT_COUPLED.pdf
    Reply  Tue Nov 5 18:37:59 2019, anchal, DailyProgress, FSS, FSS Diagnostics - TTFSS Testpoint Spectrum Data FSS_TP_Spectrum.pdf
       Reply  Sat Nov 9 19:28:36 2019, anchal, DailyProgress, FSS, FSS Diagnostics - Loop nonlinearity Test NFSS_NonLinearity_Test.pngSFSS_NonLinearity_Test.pngsignal-attachment-2019-11-09-195635.jpeg
          Reply  Mon Nov 11 20:42:49 2019, anchal, DailyProgress, FSS, FSS Diagnostics - Two Tone Test NFSS_RFPD_SN009_TF_11-11-2019_183131.pdfSFSS_RFPD_SN010_TF_11-11-2019_203310.pdfFSStwoToneTest.pdf
             Reply  Tue Nov 12 18:36:59 2019, anchal, DailyProgress, FSS, FSS Diagnostics - Two Tone Third Order Intermodulation Test FSStwoToneThirdOrderIM.pdf
                Reply  Thu Nov 14 12:19:32 2019, rana, DailyProgress, FSS, FSS Diagnostics - Two Tone Third Order Intermodulation Test 
                   Reply  Tue Nov 19 18:51:02 2019, anchal, DailyProgress, FSS, FSS Diagnostics - Second-order Distortion Calculation FSSDistortionCalc.pdfFSSDistortion.zip
                      Reply  Mon Dec 9 19:54:44 2019, anchal, DailyProgress, FSS, FSS Diagnostics - How much distortion affects the functioning of PDH? 
       Reply  Wed Nov 27 13:59:24 2019, anchal, DailyProgress, FSS, FSS Diagnostics - TTFSS TP1 TimeSeries NFSS_TP1_Oscilloscope.pdf
          Reply  Wed Nov 27 15:17:51 2019, anchal, DailyProgress, FSS, FSS Diagnostics - Quick HF OLTF of NFSS NFSS_OLTF_HF.pdf
             Reply  Wed Nov 27 16:31:20 2019, rana, DailyProgress, FSS, FSS Diagnostics - Quick HF OLTF of NFSS 
                Reply  Wed Dec 4 18:11:09 2019, anchal, DailyProgress, FSS, Free running laser frequency noise spectrum PMCErrorSignals.pdf
                   Reply  Thu Dec 5 18:25:11 2019, rana, DailyProgress, FSS, Free running laser frequency noise spectrum 
                   Reply  Tue Dec 17 18:29:58 2019, anchal, DailyProgress, FSS, Need for ISS? 
                      Reply  Wed Dec 18 18:40:32 2019, anchal, DailyProgress, FSS, Maybe the NPRO Laser isn't bad after all NorthLaserRINAnalysis.pdf
                         Reply  Wed Dec 18 22:03:17 2019, rana, DailyProgress, FSS, Maybe the NPRO Laser isn't bad after all 
                            Reply  Fri Dec 20 15:00:30 2019, anchal, DailyProgress, FSS, PZT, EOM to RIN TF Measurement NorthLaserPZTEOMtoRINTF.pdf
                               Reply  Fri Dec 20 18:08:44 2019, anchal, DailyProgress, FSS, PZT, EOM to RIN TF Measurement Through FSS NorthLaserPZTEOMtoRINTFThruFSS.pdf
                                  Reply  Tue Jan 7 17:59:20 2020, anchal, DailyProgress, FSS, NPMC TF NPMC_TF.pdf
       Reply  Thu Dec 12 19:15:55 2019, anchal, DailyProgress, FSS, FSS Diagnostics - Beatnote Spectrum wrt Laser Power and Modulation Index BeatnoteSpectrumwrtPowerandModindex.pdf
       Reply  Tue Dec 17 16:55:07 2019, anchal, DailyProgress, FSS, FSS Diagnostics - TTFSS North U7 Boost Stage Input-Output TimeSeries NFSS_UT_TS_Analysis.pdf
    Reply  Tue Nov 12 11:39:48 2019, anchal, DailyProgress, FSS, FSS Diagnostics - RFPD RF Ouput under inspection 
    Reply  Fri Dec 13 16:24:02 2019, anchal, DailyProgress, FSS, FSS Diagnostics - RFPD Circuit Latest Available Photos SN009.jpgSN010.jpgSN009.jpgSN010.jpg
    Reply  Fri Dec 13 17:44:05 2019, anchal, DailyProgress, FSS, FSS Diagnostics - RFPD RF Coupled Output Offset 
       Reply  Mon Jan 13 19:04:38 2020, anchal, DailyProgress, FSS, FSS Diagnostics - SN009 (North RFPD) Notch Improvement Attempt SN009.jpgSN009_D980454-00-C.pdfSN009_Notch_Improvement_Attempt.pdf
          Reply  Tue Jan 14 18:19:33 2020, anchal, DailyProgress, FSS, FSS Diagnostics - SN009 (North RFPD) Notch Improved! SN009.jpgSN009_D980454-00-C.pdfSN009_Notch_Improvement_Attempt.pdf
             Reply  Thu Jan 16 11:17:15 2020, anchal, DailyProgress, FSS, FSS Diagnostics - SN010 (South RFPD) Notch Improvement Attempt SN010.jpgSN010_D980454-00-C.pdfSN010_Notch_Improvement_Attempt.pdf
                Reply  Thu Jan 16 20:18:44 2020, anchal, DailyProgress, FSS, FSS Diagnostics - SN010 (South RFPD) Notch Improved SN010.jpgSN010_D980454-00-C.pdfSN010_Notch_Improved.pdf
                   Reply  Mon Jan 27 18:29:19 2020, anchal, DailyProgress, FSS, FSS Diagnostics - RFPD RF Out Spectrum FSS_RFPD_RFOut_Spectrum.pdf
Message ID: 2479     Entry time: Tue Nov 12 18:36:59 2019     In reply to: 2477     Reply to this: 2480
Author: anchal 
Type: DailyProgress 
Category: FSS 
Subject: FSS Diagnostics - Two Tone Third Order Intermodulation Test 

In line with industrial practices, I did two tone third order intermodulation test today on the FSS RFPDs. This test was inspired by procedure described in this technical note by MiniCircuits and this paper at IEEE.

Method

  • Similar to previous measurement, two RF tones are generated using Moku.
  • However, now, they are separated by an audio frequency, 10 kHz in our case. This is marked as DF in the plots.
  • These tones are centered around the resonant frequency of the RFPD marked as CF in the plots.
  • The two signals are combined together through ZFSC-2-1W+.pdf, but this time all ports of the combiner have an attenuator on it.
  • 3 dB attenuators at the input port and 6 dB at the output port. This was mentione din MiniCircuits as a step to improve impedance matching near the combiner.
  • Ideally, two low pass filters also should be put at the input port, but I couldn't find any with high enough cut-off frequency.
  • The combined source signal was getting attenuated by 8.75 dB. So I just drove the input signals higher by this amount.
  • The Source signal is fed to the Test IN of the RFPD and RF out is read through AG4395A.
  • The power in each harmonic is calculated from the spectrum and plotted together against source power.
  • Since all RF signals are the near-resonant peak of the photodiode, there would be little to no difference in TF seen by them.

Inference:

  • I think because of the 100 kOhm resistor at the Test In port of RFPDs makes the source signal too feeble.
  • I'm just measuring instrument noise upto source power of -10 dB. I can't go above 0 dB in current setup atleast.
  • At 0 dB source power, which is equivalent to 3 uApk photocurrent from the photodiode, the third-order harmonics are 60 dB lower.
  • One way of reporting this is, Spurious Free Dynamic Range (SFDR) at 36(37) MHz is 60 dBc at 0 dBm source power of SN009 (SN010).
  • Another way this figure is reported in industry is by extrapolating at which point the third-order harmonic power becomes the same as fundamental.
  • But I do not have enough distortion showing data points to extrapolate to calculate the intercept.
  • Last plot is when I connected the cables together which go to DUT. We see SFDR of 60 dBc here itself.
  • The last two data points are when input range of AG4395A are very high and hence has increased noise floor.
  • So probably in my measurements also, I'm just seeing distortion due to measurement apparatus itself.
  • But this at least sets an upper bound of distortion to SFDR of 60 dBc at the resonant frequencies (within the errors that I, a graduate student, can make).

Datasheet for MAX4107

  • The datasheeet says that between 30-40 MHz, the SFDR is approximately 50 dBc (this is actually lower than what we measured).
  • Also, the third-order intercept is mentioned at 15 dBm source power.

Data

Attachment 1: FSStwoToneThirdOrderIM.pdf  25 kB  | Hide | Hide all
FSStwoToneThirdOrderIM.pdf FSStwoToneThirdOrderIM.pdf FSStwoToneThirdOrderIM.pdf
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