Written by Yuta

Now that the mystery of the PD signal chain and the BS actuation efficiency for Michelson are solved (see alog #10213 and #10127), I corrected what we've found missing/wrong in the noise budget (NB) model.

[Motivation]
We wanted to check the validity of the NB model.


[What are missing/wrong?]
Things that were missing/wrong in the NB model "DRMI_Live.slx" copied from LLO was;

• The calibration for the suspension model was wrong
• Analog/Digital AI filters are not implemented
• Whitening gain values for PDs were missing (e.g. H1:LSC-REFLAIR_A_RF45_WHITEN_GAIN)
• Gains in the PD filter banks were missing (e.g. H1:LSC-REFLAIR_A_RF45_I_GAIN)
• Analog/Digital AA filters were wrong
• Choice of AIR and in-vac PDs were missing
• Optickle gives demodulated signal with the demod gain of 0.5. So, the factor of 2 was missing.
• The PD cable loss was not considered (I'm not sure how to treat with this kind of things in the Full IFO NB model)

[What files do I use?]
The NB model and functions for our Michelson lives in /ligo/svncommon/NbSVN/aligonoisebudget/trunk/MICH/H1. They are based on LLO DRMI NB model but corrected the things mentioned above.
The essential files are

run_NB.m: main script
make_MICH.m: function called from run_NB.m
./Params/paramNbH1MICHtest.m: parameter file
MICH_Live.slx: simulink model

They use the following Optickle files which live in /ligo/svncommon/IscCVS/iscmodeling/LentickleAligo/PRMI/ParamFiles for optical simulation.

optL1DRM.m: constructs Optickle model
probesH1DRM_00.m: puts probes for the Optickle model
paramH1MICH.m: parameter file


[Result]
Attached plot shows the comparison of the OLTF of the MICH loop from the measurement (see alog #10127) and from the NB model. They agree within ~20%. This error mainly comes from the power measurement error.

Note that the Matlab function "linmod" doesn't work correctly when the Optickle block is put in the NB simulink model. Do something like;

[systm,flexTfs] = linFlexTf('MICH_Live');
systm = prescale(systm,{freq(1) freq(end)});
systm = linFlexTfFold(systm,flexTfs);

to plot transfer functions (Thanks to Chris Wipf!).