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Homework Help: Time Domain Functions to Frequency Domain

  1. Nov 23, 2008 #1
    How do you convert functions from the time domain, to the frequency domain
    For example: cos(250t + 30degrees) is what in the frequency domain?
    Are there some general steps I can follow to do this?
     
  2. jcsd
  3. Nov 23, 2008 #2
    Your going to need your laplace transformations table.
    Basically you can split 250t do that part which would work out to:

    for the 250 part its entry #2 in the table

    F(S) = (250/s ^2) + L(30 deg)


    The L above stands for laplace transform i still left that part in the time domain. I would convert 30 deg. to radians which is a constant and then use that number over s. That is entry number 1 in the table.
     
  4. Nov 23, 2008 #3

    Redbelly98

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    The technique for doing that is the Fourier Transform. Try a google search on that, as well as "Fourier Series". These might be in your course textbook also.
     
  5. Nov 23, 2008 #4

    Redbelly98

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    I think Laplace transforms may be overkill hill. The OP is just looking for the frequency-domain representation, i.e. the frequency spectrum.
     
  6. Nov 23, 2008 #5
    Your correct, no argue from here, im a 3rd year Electrical engineering student new to this site and intend on staying around. :) Great palce, and sorry to go off topic.
     
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