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  Fri Oct 4 13:41:44 2019, anchal, Notes, FSS, FSS Plant Model FSS_Plant_Zero_Sim.pdfPlantModel.pdfPlantModel.zip
    Reply  Fri Oct 4 14:56:42 2019, Ian MacMillan, Notes, FSS, FSS Plant Model PlantModelCircuit.pdf
       Reply  Tue Oct 8 10:41:43 2019, anchal, Notes, FSS, FSS Plant Model 
          Reply  Mon Oct 14 12:54:41 2019, anchal, Notes, FSS, FSS Plant Model v2 FSS_Plant_Zero_Sim.pdfPlantModelv2.pdfPlantModelv2.zip
             Reply  Tue Oct 22 13:07:45 2019, Ian MacMillan, Notes, FSS, FSS Plant Model v2 PlantDig.pdfEOM_Transfer_Function.pdfPZT_Transfer_Function.pdf
                Reply  Thu Oct 24 11:42:06 2019, Ian MacMillan, Notes, FSS, FSS Plant Model v2 
                   Reply  Tue Dec 3 17:27:54 2019, Ian MacMillan, Notes, FSS, FSS Plant Model v2 IMG_8065.jpegIMG_8069.jpeg
                      Reply  Mon Dec 9 18:08:13 2019, Ian MacMillan, Notes, FSS, FSS Plant Model v2 OutputGraphsTransferFunction.pdf_Circuit_Design_V1.zip
                         Reply  Tue Dec 10 11:57:58 2019, Ian MacMillan, Notes, FSS, FSS Plant Model v2 IMG_8124.jpeg
                            Reply  Thu Dec 12 11:54:11 2019, Ian MacMillan, Notes, FSS, FSS Plant Model v2 PZT_LowFq_V1.pdfPZT_HighFq_V1.pdfEOM_LowFq_V1.pdfEOM_HighFq_V1.pdf
                               Reply  Thu Dec 12 19:05:33 2019, rana, Notes, FSS, FSS Plant Model v2 
                                  Reply  Mon Dec 16 09:43:56 2019, Ian MacMillan, Notes, FSS, FSS Plant Model v2 PZT_TF.pdfEOM_TF.pdfNon-Moku_Data_PlantCir_V1.zip
                                     Reply  Tue Jan 14 13:30:39 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 EOM_TF_V1.pdfPZT_TF_V1.pdfPlant_CIR_TF.zip
                                        Reply  Tue Jan 14 13:32:16 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 FSSPlantModelV2SCH.pdfFSSPlantModelV2.pdfPlant_Circuit_Board_Eagle.zip
                                           Reply  Tue Jan 28 13:27:25 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 LIGO-D2000020-v1.pdfBOARD_LIGO-D2000020-v1.pdfEagle_LIGO-D2000020-v1.zip
                                              Reply  Mon Feb 10 12:46:17 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 
                                              Reply  Fri Feb 14 16:46:47 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 TFAG4395A_14-02-2020_155048.pdfTFAG4395A_14-02-2020_165608.pdf
                                                 Reply  Tue Feb 18 15:42:46 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 PZT_TF_V1.pdfEOM_TF_V1.pdfTransfer_Functions_FSS.zip
                                                    Reply  Tue Mar 3 17:13:04 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 image.pngPLT_Spectrum.pdf20200303_IanSimPlant.zipPLT_Spectrum.pdfPLT_TF.pdf
                                                       Reply  Wed Mar 11 15:40:50 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 TFSR785_06-03-2020_135844_PZT.pdfTF_V1.zip
                                                          Reply  Thu Mar 12 16:21:49 2020, Ian MacMillan, Notes, FSS, FSS Plant Model v2 TFSR785_10-03-2020_175129.pdfTFSR785_10-03-2020_175129.txt
                                                          Reply  Thu Mar 12 17:18:51 2020, rana, Notes, FSS, FSS Plant Model v2 
Message ID: 2485     Entry time: Tue Dec 3 17:27:54 2019     In reply to: 2465     Reply to this: 2489
Author: Ian MacMillan 
Type: Notes 
Category: FSS 
Subject: FSS Plant Model v2 

The new circuit design has been built and is shown below. I tested the transfer functions and the PZT path looks good by eye but the EOM path looks like there is a solder point that is bad. I will show the graphs when I have them done.

 

Quote:

With discussions with Anchal and some reading

It seems impossible to create a casual circuit with a zero phase shift. (See this for more) 

If we have a circuit with an impulse response h(t) and transfer function H(f)=F[h(t)] where H(-f)=H*(f). For the filter to cause no phase shift then ∠H(f)=0 for a complex exponential input for all f. It is also impossible to have a constant phase shift unless that phase shift is zero.

Therefore "filter does not change the phase at all, then H(f) is a real-valued function, and because of the conjugacy constraint, it is also an even function of f. But then its Fourier transform h(t) is an even function of time, and thus the filter cannot be causal (except in trivial cases): if its impulse response is nonzero for any particular t>0, then it is also nonzero for −t (where −t<0)" 

Because this can't be done casually, it should be done using a Field Programmable Gate Array. Unfortunately, I don't think we have access to one. I am reading up on the Moku FIR Filter builder to find out if we can program it to do what we want.

Quote:

I have designed a passive circuit that seems to match the ideal transfer functions in shape. Scaling should just be a game of playing with the values of the resistors and capacitors. The phase still seems to be an issue. There is an unwanted phase shift from 0 -> -90.

The next step is trying to finalize the values for the resistors and caps. Possibly model in zero if I have time. Then build and test. Also fix the phase.

Quote:

I have updated the plant model to contain the cavity pole also. Cavity pole is a pair of positive and negative real poles, so it is hard (or maybe impossible) to imitate it exactly with an electronic circuit. Or maybe, my analysis is wrong.

Nevertheless, I have for now made this circuit which has a second-order pole, so it correctly matches the magnitude of the model transfer function up to 1 MHz for both PZT and EOM paths. Note that the elliptical filter is not included in this as we can connect the circuit to Test port 1 which injects just before the filter in LIGO-D0901894. Also, for the gains in EOM path, I had to add some factors to make it the same as the model transfer function. All components are calculated for E12 series resistors and capacitors.

Attached is a pdf of the notebook which contains all the mathematics in latex and a zip file with all files to recreate and further work on this. Ian can use these as support to learn zero further.

 

 

 

Attachment 1: IMG_8065.jpeg  3.837 MB  | Hide | Hide all
IMG_8065.jpeg
Attachment 2: IMG_8069.jpeg  1.430 MB  | Hide | Hide all
IMG_8069.jpeg
ELOG V3.1.3-