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Entry  Mon Mar 27 20:41:21 2017, rana, gautam, Update, PSL, PMC DAQ assay for feed-forward integration TEK00000.PNG20170327_194931.jpg20170327_204554.jpg
    Reply  Wed Mar 29 11:41:19 2017, gautam, Update, PSL, PMC DAQ assay for feed-forward integration C1ALS_PSLnamespace.pngPMCcheckout.pdfD980352-A-40m_151119.pdf
       Reply  Thu Mar 30 00:16:09 2017, gautam, Update, PSL, PSL NPRO PZT calibration 
          Reply  Mon Apr 3 17:25:13 2017, gautam, Update, PSL, PSL NPRO PZT calibration PDHerr.pdfNPROcalib.pdf
             Reply  Tue Apr 4 17:27:58 2017, rana, Update, PSL, PSL NPRO PZT calibration 
       Reply  Thu Mar 30 18:11:01 2017, rana, Update, PSL, PMC DAQ assay for feed-forward integration 
          Reply  Mon Apr 3 23:07:09 2017, gautam, Update, PSL, PMC DAQ assay for feed-forward integration 
             Reply  Tue Apr 11 00:38:37 2017, gautam, Update, PSL, PMC demod moved off servo board PMC_Ctrl_spec.pdf
                Reply  Wed Apr 12 00:36:53 2017, gautam, Update, PSL, PMC demod moved off servo board PMC_digitalSpec.pdfPMC_DAQ_spectra.pdf
                   Reply  Tue Apr 18 01:01:03 2017, gautam, Update, PSL, PMC OLTF measured, DAQ channels calibrated PMCspectra_calibrated.pdfPMC_MEDMs.png
                      Reply  Tue Apr 18 16:10:00 2017, gautam, Update, PSL, PMC OLTF measured, DAQ channels calibrated PMC_OLTF_170418.pdf
                         Reply  Tue Apr 18 23:37:15 2017, rana, Update, PSL, PMC OLTF measured, DAQ channels calibrated 
                         Reply  Wed Apr 19 15:13:30 2017, gautam, Update, PSL, PMC/MCL multicoherence PMC_MCL_multicoherence.pdf
Message ID: 12939     Entry time: Tue Apr 11 00:38:37 2017     In reply to: 12926     Reply to this: 12940
Author: gautam 
Type: Update 
Category: PSL 
Subject: PMC demod moved off servo board 

As discussed at the Wednesday meeting last week, I tried moving the demodulation of the PMC error signal off the PMC servo board, by using some minicircuits components. This is just a quick summary elog, more details to follow tomorrow.

  • I used the Mini Circuits ZAD-6+. This is a level 7 mixer, and the LO board puts out ~16dBm, so I replaced the existing 3dB attenuator between the LO board and the input to the PMC servo board with a 9dB attenuator.
  • On the RF side, I retained the 35.5 MHz bandpass filter on the PD input.
  • On the IF output, I used an in-line 50ohm terminator in series with a minicircuits BLP1.9+ low pass filter
  • The mixer output was routed to the FP1 test input of the servo board
  • After some twiddling with the demod phase MEDM screen, I was able to lock the PMC. I've not done a thorough characterization of the loop with the current configuration, this will be done tomorrow. But the PMC and IMC have been stably locked for the last couple of hours...

During the course of this work, I noticed that there was a 35.5MHz line (at ~-55dBm) in the 4-pin LEMO DAQ outputs even when all other inputs to the servo board were terminated. So it seems like this pickup is not coming from the RFPD or demod path. The LO board has a shield enclosure similar to what we have on the LSC demod boards, but perhaps this shield does not enclose the full RF path, and there is some residual pickup between the two cards in close proximity in the Eurocrate?

On the bright side, with this demod setup, the higher harmonic peaks seem to be significantly suppressed.

In particular, the 3x35.5 MHz peak which was very prominent when I looked at these spectra with the nominal demod setup, seems to be much suppressed. 

I'm leaving the PMC servo in this configuration (off servo board demodulation using minicircuits parts) overnight.

Attachment 1: PMC_Ctrl_spec.pdf  27 kB  | Show | Show all
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