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Entry  Wed Nov 23 17:48:16 2016, rana, koji, Update, IOO, How bad is the McWFS? 
    Reply  Sat Nov 26 19:16:28 2016, Koji, Update, IOO, IMC WFS Demod board measurement & analysis WFS_demod_response.pdfWFS_demod_noise.pdfWFS_demod_noise_plan.pdfScreen_shot_2011-07-01_at_11.13.01_AM.png
       Reply  Tue Nov 29 17:45:06 2016, Koji, Update, IOO, IMC WFS Demod board measurement & analysis demod.pdfWFS_demod_response.pdfWFS_demod_noise.pdf
          Reply  Tue Nov 29 18:35:32 2016, rana, Update, IOO, IMC WFS Demod board measurement & analysis 
             Reply  Fri Dec 2 18:02:37 2016, Koji, Update, IOO, IMC WFS Demod board measurement & analysis WFS_demod_noise_orig.pdfWFS_demod_noise_mod.pdf
                Reply  Sat Dec 3 13:27:35 2016, Koji, Update, IOO, IMC WFS Demod board measurement & analysis WFS_demod_noise.pdfdemod.pdf
                   Reply  Tue Dec 6 13:37:02 2016, Koji, Update, IOO, IMC WFS Demod board measurement & analysis demod.pdfWFS_error_noise.pdf
                      Reply  Tue Dec 6 16:47:40 2016, Koji, Update, IOO, IMC WFS whitening filter investigation D990196-C.pdf
                         Reply  Tue Dec 6 17:54:08 2016, Koji, Update, IOO, IMC WFS whitening filter investigation 34.png
                            Reply  Tue Dec 6 22:41:49 2016, Koji, Update, IOO, IMC WFS whitening filter investigation 
                               Reply  Tue Dec 13 17:26:42 2016, Koji, Update, IOO, IMC WFS whitening filter investigation 
                                  Reply  Thu Dec 15 03:46:19 2016, rana, Update, IOO, IMC WFS whitening filter investigation 
Message ID: 12670     Entry time: Tue Dec 6 17:54:08 2016     In reply to: 12669     Reply to this: 12671
Author: Koji 
Type: Update 
Category: IOO 
Subject: IMC WFS whitening filter investigation 

The input resistor 909Ohm of AD602 was shorted. I've confirmed that the gain (= attenuation by voltage division) was increased by a factor of 10.
This modification was done for WFS2-I1 and WFS2-Q1. Also the thick film resistors for the WFS2-I1 channel was all replaced with thin film resistors.

Attachment 1 shows the comparison of the noise levels. The curves were all calibrated referred to the response of the original whitening filter configuration.
(i.e. measurement done after the gain change was compensated by the factor of 10.)

Now the AF chain is not limited by the noise in the whitening filter board. (Brown)
In fact, this noise level was completely identical between I1 and Q1. Therefore, I don't think we need this resistor replacement for the whitening filter board.

We can observe the improvement of the overall noise level below 10Hz. (Comparison between green and red/blue)
As the signal level goes up, the noise above 100Hz was also improved.

Now we need to take care of the n x 0.7Hz feature which is in the demod board...
 

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