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Entry  Sat Sep 10 14:55:28 2011, Keiko, Update, LSC, 3f demodulation board check 
    Reply  Sat Sep 10 16:10:42 2011, Keiko, Update, LSC, 3f demodulation board check REFL33-input-filter.png
       Reply  Sat Sep 10 18:57:52 2011, Keiko, Update, LSC, 3f demodulation board check 
          Reply  Sun Sep 11 15:19:39 2011, kiwamu, Update, LSC, phase delay in RF signals 
       Reply  Sun Sep 11 22:36:32 2011, Keiko, Update, LSC, 3f demodulation board check REFL33.pngREFL165.png
          Reply  Mon Sep 12 13:24:07 2011, Keiko, Update, LSC, 3f demodulation board check 
             Reply  Mon Sep 12 16:27:01 2011, Keiko, Update, LSC, 3f demodulation board check 
                Reply  Mon Sep 12 18:40:35 2011, Keiko, Update, LSC, 3f demodulation board check 
                   Reply  Tue Sep 13 15:00:25 2011, Keiko, Update, LSC, 3f demodulation board check WF33.pdfWF165.pdf
                      Reply  Tue Sep 13 23:08:51 2011, Keiko, Update, LSC, 3f demodulation board check REFL33-modified.pngREFL165-modified.png
                         Reply  Thu Sep 15 01:06:20 2011, Keiko, Update, LSC, 3f demodulation board check 
                            Reply  Fri Sep 16 21:26:12 2011, Keiko, Update, LSC, 3f demodulation board check 
Message ID: 5385     Entry time: Sun Sep 11 22:36:32 2011     In reply to: 5378     Reply to this: 5386
Author: Keiko 
Type: Update 
Category: LSC 
Subject: 3f demodulation board check 

Filters at the RF inputs of REFL33 and REFL165 demodulation boards were measured again. The filters will be totally fine for 33MHz and 165MHz.

Last time I forgot to calibrate the cable lengths, therefore the phase delay of the measurement included the cable lengths. This time the measurements were done for REFL33 and REFL165 demod board with calibration. As the cable lengths were calibrated, the shown plots (Fig.1 and Fig.2) do not include the phase delay dues to measurement cables. Please note that the x-axis is in linear. The phase delays of both boards seems to be not too steep (it will not affect anyway, as Kiwamu pointed out in his comment on the previous post). You can see that the two filters do not filter 33MHz and 165MHz component out.

REFL33.png

Fig.1 A response of a filter which is placed just after the RF input of the demodulation board for REFL33. X-axis is shown in linear (~50MHz).

REFL165.png

Fig.2 A response of a filter which is placed just after the RF input of the demodulation board for REFL165.

 

Quote:

There is a LP filter just after the RF input of an demodulation board (its schematic can be found as D990511-00-C on DCC). I have checked if the 3f freq, 33MHz, can pass  this filter. The filter TF from the RF input to RF monitor (the filter is between the input and monitor) on REFL33 demo-board was measured as shown in Fig. 1. At 33MHz, the magnitude is still flat and OK, but the phase is quite steep. I am going to consider if it is ok for the PDH method or not.

REFL33-input-filter.png

 Fig. 1 Transfer function from the RF input to RF monitor on the REFL33 demodulation board. At 33MHz, a very steep phase is applied on the input signal.

Quote:

 To check the demodulation boards for REFL33 and REFL165, a long cable from ETMY (SUS-ETMY-SDCOIL-EXT monitor) is pulled to the rack on Y side.

(1) A filter just after the RF input and (2) transfer function from the RF input to the demodulated signal will be checked for the two 3f demod boards to confirm that they are appropriate for 33 and 165 MHz.

 

 

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