40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  PSL  Not logged in ELOG logo
Entry  Mon Jun 11 15:03:15 2018, anchal, DailyProgress, ISS, Loop Gain Transfer Function analysis on LTspice ISSLoopGainAnalysis.pdfISSLoopGainTFwithAOMDCG1.11.pdf
    Reply  Wed Jun 13 18:04:32 2018, anchal, DailyProgress, ISS, Loop Gain Transfer Function analysis on LTspice ISSMeasuredTF06-13-2018.pdfISSLTSpiceTF.pdf
Message ID: 2201     Entry time: Mon Jun 11 15:03:15 2018     Reply to this: 2202
Author: anchal 
Type: DailyProgress 
Category: ISS 
Subject: Loop Gain Transfer Function analysis on LTspice 

With the circuit of Johannes, I ran LT spice analysis with modeling cavity pole and AOM delay to get an estimate of how the loop gain would look like. Attached is a plot of the transfer function of loop gain and the circuit schematic used. Here I used this post of Johannes on elog to use DC Gain of AOM as 1.11 dB. But in case, this changes, I have a running code which will output the new unit gain frequencies and phase margins. I'll implement this into a board soon and move forward by optimizing the choice of elements with help from LISO.
I'm seeking input on anything which makes the frequency curve as shown here less than satisfactory.

Attachment 1: ISSLoopGainAnalysis.pdf  101 kB  Uploaded Mon Jun 11 16:09:50 2018  | Hide | Hide all
ISSLoopGainAnalysis.pdf
Attachment 2: ISSLoopGainTFwithAOMDCG1.11.pdf  24 kB  Uploaded Mon Jun 11 16:10:05 2018  | Hide | Hide all
ISSLoopGainTFwithAOMDCG1.11.pdf
ELOG V3.1.3-