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Homework Help: Signal Analysis

  1. Aug 17, 2012 #1
    1. The problem statement, all variables and given/known data
    Hi ,
    The problem is how to analysis this signal in terms of time segments to understnd the characteristics/pattern of this signal
    146493896.png

    2. Relevant equations

    There is no relevant equtions

    3. The attempt at a solution

    I have tried to use :
    RMS
    Wavlet
    FFT
    But which one of them can give us a better understing of the system,

    Thanks,
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Aug 17, 2012 #2

    lewando

    User Avatar
    Homework Helper
    Gold Member

    Your problem statement is fairly unconstrained so--

    For frequency analysis, consider making a spectrogram, a 3 dimensional graph (frequency vs amplitude vs time).

    For amplitude analysis, experiment with various moving average (RMS) plots.
     
  4. Aug 17, 2012 #3

    gneill

    User Avatar

    Staff: Mentor

    Presumably you have a data set that corresponds to the graph, and not just the graph alone? You might want to investigate the use of the Lomb-Scargle Periodogram method to tease out the underlying frequency components of the signal.
     
  5. Aug 18, 2012 #4
    Thanks for the response,


    Well, I have applied frequency domain


    Matlab code:

    m=fft(x)
    n=length(x)
    power=abs(m(1:floor(n/2))).^2
    nyquist=1/2
    freq=((1:n/2)/(n/2)*nyquist)*5000
    figure
    plot(freq,power)
    xlabel('Frequency (Hz)')
    ylabel('Power')
    title('Power Spectrum of Signal')
    grid on
    977009973.png

    amp=abs(m(1:floor(n/2)))
    figure
    plot(freq,amp)
    xlabel('Frequency (Hz)')
    ylabel('Amplitude')
    title('Amplitude Spectrum of Signal')
    grid on
    975500764.png




    But I am not quite sure which one of them is best/correct,any suggestion,
    Thanks
     
  6. Aug 18, 2012 #5

    lewando

    User Avatar
    Homework Helper
    Gold Member

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