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Entry  Wed Jul 16 22:17:40 2014, Akhil, Summary, Electronics, Bode Plots and complete Characterization of Frequency Counter Phase_Data.zipBode100MHz.png
    Reply  Wed Jul 16 23:02:16 2014, Koji, Summary, Electronics, Bode Plots and complete Characterization of Frequency Counter 
       Reply  Fri Jul 18 19:32:50 2014, Akhil, Summary, Electronics, Filters used inside the Frequency Counter TheoreticalGainPlot.pngTFexpected.png
          Reply  Mon Jul 21 12:16:27 2014, Akhil, Summary, Electronics, Filters used inside the Frequency Counter FC_TF_Characterization.png
Message ID: 10222     Entry time: Wed Jul 16 22:17:40 2014     Reply to this: 10223
Author: Akhil 
Type: Summary 
Category: Electronics 
Subject: Bode Plots and complete Characterization of Frequency Counter 

Goal:

To estimate the transfer function and the noise in the FC that is a part of the FOL-PID loop.

Measurements Taken:

The setup used for the measurements is described in my previous elogs.

The input modulation signal and the FC output were recorded simultaneously for a certain period of time and the phase and gain are estimated from the data.

Analysis(Data and code attached):

The recordings must contain equal number of data points(around 6000 data points in my measurements) for analysis.

The steps I followed to generate these plots are:

  • Took the FFT of both FC out data(from FC) and Modulation input(from SRS via ADC).
  • Estimated the phase angles at the particular modulation frequencies from the FFT data(in Matlab using  angle(x) for phase at the frequency f(x);x: is the frequency bin)
  • Then for the phase of the system at a particular modulation frequency, 

                              Phase(system) =Phase(FC Signal) - Phase(Input Signal)

  • Plotted the acquired phase vs the modulation frequency on a Semi-log graph.

Results:

From the plots its can be inferred that :the delay of the FC is almost 0 until the modulation of 0.1 Hz. Then there are phase shifts of  +/- 180 degrees showing that the system has multiple poles and zeroes(will be estimated after I have phase plots at few more carrier frequencies).

To Do Next

Phase plots for varying carrier frequencies and different sampling times.

Installation of FC inside the 40m.

Attachment 1: Phase_Data.zip  1.202 MB
Attachment 2: Bode100MHz.png  16 kB  Uploaded Thu Jul 17 00:36:22 2014  | Hide | Hide all
Bode100MHz.png
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