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Entry  Mon Sep 20 15:42:44 2021, Ian MacMillan, Summary, Computers, Quantization Code Summary 472px-Typical_State_Space_model.svg.pngBiquad_filter_DF-IIx.svg.pngSS-IIR-TF.pdf
    Reply  Wed Sep 22 14:22:35 2021, Ian MacMillan, Summary, Computers, Quantization Noise Calculation Summary IIR64-bitnoisespectrum.pdf
       Reply  Mon Sep 27 12:12:15 2021, Ian MacMillan, Summary, Computers, Quantization Noise Calculation Summary 
          Reply  Mon Sep 27 16:03:15 2021, Ian MacMillan, Summary, Computers, Quantization Noise Calculation Summary DeltaNoiseSpectrum.pdf
             Reply  Mon Sep 27 17:04:43 2021, rana, Summary, Computers, Quantization Noise Calculation Summary 
                Reply  Thu Sep 30 11:46:33 2021, Ian MacMillan, Summary, Computers, Quantization Noise Calculation Summary SS-IIR-Bode.pdfPSD_32bit.pdfPSD_64bit.pdf
                   Reply  Wed Nov 24 11:02:23 2021, Ian MacMillan, Summary, Computers, Quantization Noise Calculation Summary PSD_IIR_all.pdf
                      Reply  Wed Nov 24 13:44:19 2021, rana, Summary, Computers, Quantization Noise Calculation Summary 
                         Reply  Tue Dec 7 10:55:25 2021, Ian MacMillan, Summary, Computers, Quantization Noise Calculation Summary DF2_TS.pdfBIQ_TS.pdfScreen_Shot_2021-12-07_at_11.47.57_AM.pngPSD_COMP_BIQ_DF2.pdfPSD_COMP_SS_DF2.pdf
                            Reply  Fri Dec 10 13:02:47 2021, Ian MacMillan, Summary, Computers, Quantization Noise Calculation Summary G0900928-v1_(dragged).pdfPSD_COMP_BIQ_DF2.pdfInput_PSD.pdfInput_Filter.pdfQuantizationN.zip
                               Reply  Mon May 9 15:32:14 2022, Ian MacMillan, Summary, Computers, Quantization Noise Calculation Summary SUS-ETMX_SUSYAW3_0.0.pdfLowNoiseBiquad2.pdfquant_noise_floor.pdf
Message ID: 16492     Entry time: Tue Dec 7 10:55:25 2021     In reply to: 16482     Reply to this: 16498
Author: Ian MacMillan 
Type: Summary 
Category: Computers 
Subject: Quantization Noise Calculation Summary 

[Ian, Tega]

Tega and I have gone through the IIR Filter code and optimized it to make sure there aren't any areas that force high precision to be down-converted to low precision.

For the new biquad filter we have run into the issue where the gain of the filter is much higher than it should be. Looking at attachments 1 and 2, which are time series comparisons of the inputs and outputs from the different filters, we see that the scale for the output of the Direct form II filter shown in attachment 1 on the right is on the order of 10^-5 where the magnitude of the response of the biquad filter is on the order of 10^2. other than this gain the responses look to be the same. 

I am not entirely sure how this gain came into the system because we copied the c code that actually runs on the CDS system into python. There is a gain that affects the input of the biquad filter as shown on this slide of Matt Evans Slides. This gain, shown below as g, could decrease the input signal and thus fix the gain. However, I have not found any way to calculate this g.

 

 

With this gain problem we are left with the quantization noise shown in Attachment 4.

State Space:

I have controlled the state space filter to act with a given precision level. However, my code is not optimized. It works by putting the input state through the first state-space equation then integrating the result, which finally gets fed through the second state-space equation. 

This is not optimized and gives us the resulting quantization noise shown in attachment 5.

However, the state-space filter also has a gain problem where it is about 85 times the amplitude of the DF2 filter. Also since the state space is not operating in the most efficient way possible I decided to port the code chris made to run the state-space model to python. This code has a problem where it seems to be unstable. I will see if I can fix it

 

 

Attachment 1: DF2_TS.pdf  12 kB  | Hide | Hide all
DF2_TS.pdf
Attachment 2: BIQ_TS.pdf  11 kB  | Hide | Hide all
BIQ_TS.pdf
Attachment 4: PSD_COMP_BIQ_DF2.pdf  234 kB  | Hide | Hide all
PSD_COMP_BIQ_DF2.pdf
Attachment 5: PSD_COMP_SS_DF2.pdf  217 kB  Uploaded Tue Dec 7 15:16:00 2021  | Hide | Hide all
PSD_COMP_SS_DF2.pdf
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