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Entry  Fri Jul 18 17:10:57 2014, Nichin, Summary, Electronics, Characterization of demodulator boards. Demodulators_TF.pdf
    Reply  Tue Jul 22 15:50:35 2014, Nichin, Summary, Electronics, Characterization of demodulator boards. Demodulators_TF.pdf
       Reply  Wed Jul 23 11:54:27 2014, Nichin, Update, Electronics, Characterization of demodulator boards. 1.pdf2.pdf
Message ID: 10252     Entry time: Tue Jul 22 15:50:35 2014     In reply to: 10238     Reply to this: 10263
Author: Nichin 
Type: Summary 
Category: Electronics 
Subject: Characterization of demodulator boards. 

Quote:

Rack 1Y2, I took transfer function measurements for each of the following demodulator boards: REFL11, REFL33, REFL55, REFL165, AS55, POP22, POX11 and POY11.

What I did:

1) Removed the wire at PD Input to demodulator board.

2) Put the MOD output from network analyzer into PD input of board.

3) Ran a sweep from 100kHz to 100MHz.

4) Measured the transfer function between PD RF MON and PD Input. (The PD RF MON signal came out of the RF multiplexer, so the mux is included as well )

5) Put the original wire back at PD Input.

Results:

The plots clearly show an attenuation of 20dB (factor of 10) for all the demodulator boards. This explains why my transimpedance measurements are off by 10 times.

Note: for REFL 165, there was an extra 100MHz high pass filter installed at PD Input. I did not remove this and made my measurements along with this.

To Do:

a) Modify the PDFR system to calibrate out this attenuation.

b) Measure the transfer function between the input and output of RF mux, so that we can have just the transfer function between PD input an PD RF MON (for documentation's sake)

 

I repeated the exact steps above and made sure everything was back where it should be after I was done.

Reason I had to retake the measurements:

My script for acquiring data from the AG4395A network analyzer was such that it first acquired the magnitude data from channel 1 and then recorded phase data from channel 2 without holding its trace. Hence the phase and magnitude data were not exactly in sync with each other. So, when I tried to fit the data to a model using vector fitting, I ended up with very bad results.

I have now changed every single script relating to the network analyzer to just get the real and imaginary data in one go and then calculate the phase using this data.

The fitting process is now in progress and results will be up shortly.

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