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Entry  Fri Apr 15 12:17:39 2011, kiwamu, Update, LSC, 11MHz demod board : funny I-Q phase relativephase.png
    Reply  Fri Apr 15 15:15:08 2011, kiwamu, Update, LSC, 11MHz demod board : 90 degree splitter 
       Reply  Sat Apr 16 02:00:14 2011, rana, Update, LSC, 11MHz demod board : 90 degree splitter 
          Reply  Mon Apr 18 13:05:57 2011, kiwamu, Summary, LSC, demod board modification demod_board.png
             Reply  Mon Apr 18 14:11:44 2011, kiwamu, Update, LSC, RF status RF_Work_Status.png
             Reply  Thu Apr 21 21:24:41 2011, kiwamu, Update, LSC, demod board : new 90 deg splitter DSC_2949_ss.jpgDSC_2951.JPGDSC_2952_ss.jpg
                Reply  Thu Apr 21 21:46:22 2011, kiwamu, Update, LSC, demod board : new 90 deg splitter relativephase.png
                   Reply  Fri Apr 22 11:08:50 2011, kiwamu, Update, LSC, demod board AS11 : amplitude imbalance IQamplitude.png
Message ID: 4538     Entry time: Mon Apr 18 13:05:57 2011     In reply to: 4537     Reply to this: 4539   4554
Author: kiwamu 
Type: Summary 
Category: LSC 
Subject: demod board modification 

Here is the idea how we upgrade the demodulation boards.

Basically we go ahead with two steps as depicted in the cartoon diagram below.

Once we finish the first step of upgrade, the board will be ready to install although the circuit won't be awesome in terms of noise performance.

 

demod_board.png

 

* * * (details) * * *

 First of all we will replace the home-made 90 degree splitter (see this entry) by a commercial splitter, PSCQ-2-51-W+ from Mini circuit. This is the step 1 basically.

At this point the boards will be ready to use in principle. I asked Steve to get three 90 degree splitters so that we can have at least three demodulators for the dual-recycled Michelson locking.

If they work very fine we will buy some more 90 degree splitters for full locking.

While we try to lock the dual-recycled Michelson once we will get a Cougar amplifier, remove all ERA-5s and install it such that we don't have to gain up and down in the circuit. This is the last step.

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