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Entry  Sat Feb 20 16:20:33 2021, gautam, Update, General, Housekeeping + PRMI char IPPOSdeat.pdfTTdrift.pdfPOXnPOY.pdfPRMI.pdf
    Reply  Sun Feb 21 20:51:21 2021, rana, Update, General, Housekeeping + PRMI char 
       Reply  Tue Feb 23 00:10:05 2021, gautam, Update, General, Demod char part 1 noPreamp.pdfwithPreamp.pdf
          Reply  Wed Feb 24 11:53:24 2021, gautam, Update, General, Demod char part 2 noises_noPreamp.pdfnoises_withPreamp.pdf
             Reply  Wed Feb 24 12:11:08 2021, gautam, Update, General, Demod char part 3 noPreamp.pdfwithPreamp.pdfnoPreamp_whitened.pdfwithPreamp_whitened.pdf
                Reply  Thu Feb 25 16:50:53 2021, gautam, Update, General, PRMI sensing matrix PRMI1f_noArmssensMat.pdf
                   Reply  Thu Feb 25 20:37:49 2021, gautam, Update, General, Setting modulation frequency and checking IMC offset modFreq.pdfIMC_offset.pdf
Message ID: 15840     Entry time: Wed Feb 24 12:11:08 2021     In reply to: 15839     Reply to this: 15844
Author: gautam 
Type: Update 
Category: General 
Subject: Demod char part 3 

I did the characterization discussed at the meeting today.

  1. RF signal at 100 Hz offset from the LO frequency was injected into the PD input on the demod boards.
  2. The digitized CDS channels were monitored. I chose to look at the C1:LSC-{PD}_I_OUT and C1:LSC-{PD}_Q_OUT channels. This undoes the effect of the analog whitening, but is before the digital phase rotation.
  3. Attachments #1 and Attachments #2 are for the case where the analog whitening is not engaged, white Attachments #3 and Attachments #4 are for when the whitening is engaged, and they look the same (as they should), which rules out any crazy mismatch between the analog filter and the digital dewhitening filter.
  4. I have absorbed the flat whitening gain applied to the various PDs in the cts/V calibration indicated on these plots. So the size of the ellipse is proportional to the conversion gain.

I think this test doesn't suggest anything funky in the analog demod/whitening/AA/digitization chain. We can repeat this process after the demod boards are repaired and use the angle of rotation of the ellipse to set the "D" parameter in the CDS phase rotator part, I didn't do it today.

Attachment 1: noPreamp.pdf  235 kB  Uploaded Wed Feb 24 18:13:28 2021  | Hide | Hide all | Show all
noPreamp.pdf
Attachment 2: withPreamp.pdf  224 kB  Uploaded Wed Feb 24 18:13:36 2021  | Hide | Hide all | Show all
withPreamp.pdf
Attachment 3: noPreamp_whitened.pdf  234 kB  Uploaded Wed Feb 24 18:19:35 2021  | Show | Hide all | Show all
Attachment 4: withPreamp_whitened.pdf  219 kB  Uploaded Wed Feb 24 18:19:56 2021  | Hide | Hide all | Show all
withPreamp_whitened.pdf
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