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MATLAB - frequency modulation, need some help

  1. Aug 3, 2009 #1
    Ok I am trying to solve this problem, I will lay it out, then say what I've done so far, and I would appreciate if someone could help me figure out where I am going wrong. I am very new to MATLAB (using it for the first time) so I've only got the basics down so far.


    Message signal
    m(t) = t for 0<=t<1
    = -t+2 for 1 <= t < 2
    = 0 otherwise

    frequency modulates the carrier c(t)=cos(2*pi*fc*t), when fc=1000Hz. The frequency-deviation constant is kf=25.

    1.) Plot the message signal and its integral on two separate graphs.

    my code:

    2) Plot the FM signal
    http://img31.imageshack.us/img31/7428/equation.jpg [Broken]

    my code (which gives a funky picture leading me to believe that my integral code is wrong)

    3) Use MATLAB's Fourier-Transform routine to compute and plot the spectra of m(t) and u(t) on separate graphs.

    Unsure what to do for these

    4) Determine the modulation index, the bandwidth, and the range of the instantaneous frequency of u(t)

    not sure about these, suggestions?
    Last edited by a moderator: May 4, 2017
  2. jcsd
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