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Tue May 26 02:15:36 2020, gautam, Update, LSC, Lock acquisition portal entry
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Tue May 26 02:31:00 2020, gautam, Update, LSC, Lock acquisition sequence
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Wed May 27 20:14:51 2020, Koji, Update, LSC, Lock acquisition sequence
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Tue May 26 02:37:19 2020, gautam, Update, LSC, DARM loop measurement and fitting 
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Tue May 26 03:01:35 2020, gautam, Update, LSC, CARM loop
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Wed Jun 3 01:46:14 2020, gautam, Update, LSC, CARM loop    
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Tue May 26 03:06:59 2020, gautam, Update, LSC, PRFPMI sensing matrix 
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Tue May 26 03:26:58 2020, gautam, Update, LSC, Preliminary noise budget
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Tue May 26 14:32:44 2020, gautam, Update, LSC, Arm transmission RIN
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Wed May 27 19:36:33 2020, Koji, Update, LSC, Arm transmission RIN
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Thu May 28 18:36:45 2020, gautam, Update, LSC, Arm transmission RIN  
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Fri May 29 00:34:57 2020, rana, Update, LSC, Arm transmission RIN
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Wed Jun 3 02:14:32 2020, gautam, Update, ASC, PRC ASC improves arm transmission RIN    
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Fri Jun 19 16:30:09 2020, gautam, Update, ASC, Some thoughts about ASC 
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Tue Jul 7 14:06:10 2020, gautam, Update, ASC, Some more thoughts about ASC
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Tue May 26 16:00:06 2020, gautam, Update, LSC, Power buildup diagnostics 
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Wed May 27 17:41:57 2020, Koji, Update, LSC, Power buildup diagnostics
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Wed Jun 3 02:08:00 2020, gautam, Update, LSC, Power buildup diagnostics 
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Wed Jun 3 01:34:53 2020, gautam, Update, LSC, Lock acquisition update portal
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Wed Jun 3 03:29:26 2020, Koji, Update, LSC, Lock acquisition update portal
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Wed Jun 3 11:40:56 2020, gautam, Update, LSC, Lock acquisition update portal
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Wed Jun 3 18:49:47 2020, gautam, Update, LSC, PRG and CARM signal sign   
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Message ID: 15351
Entry time: Tue May 26 03:01:35 2020
In reply to: 15348
Reply to this: 15366
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Author: |
gautam |
Type: |
Update |
Category: |
LSC |
Subject: |
CARM loop |
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Summary:
I am able to realize ~8 kHz UGF with ~60 degrees of phase margin on the CARM loop OLTF (combination of analog and digital signal paths).
Details:
- Attachment #1 shows the measured OLTF.
- The measurement is made by using the "EXC A" bank on the CM board, with an SR785. With this technique, the measurement will be poor where the loop gain is high, as the excitation will be squished. Nevertheless, we can estimate the behavior in those regimes by using a model, and fitting it to the regions where the measurement is valid (in this case, above ~1 kHz).
- This measurement was made with IN1 Gain = +4 dB, AO gain = 0 dB, and IMC IN2 gain = 0 dB.
- The regular boost has been enabled, but no super-boosts yet, mainly because I think they consume too much phase close to the UGF.
- The modeling/fitting of this, including a more thorough characterization of the crossover, will follow...
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