Sampling theorem question

Discussion in 'Homework Help' started by Lbyan, May 7, 2007.

  1. Lbyan

    Thread Starter New Member

    May 7, 2007
    hello every body.

    i am not sure if this is the right place or not to post my question, cuz it is not really circuit related. anw here is the question

    Consider the continuous-time signal
    x(t)=15 −8⋅cos(30000πt +π / 2)− 4⋅sin(50000πt −π / 4)

    If the signal x(t) is passed through a lowpass filter that removes all frequency
    components above 20kHz,

    (ii) Write the expression for the discrete-time signal if the signal is sampled at
    fs = 40kHz. [10%]

    (iii) Calculate the frequency f, 0 < f < 0.5 fs , of the sinusoid that yields samples
    identical to those obtained by the sampling rate of 40kHz. Comment on the
    result. [15%]

    for the first part i guess all wat i have to do is multiply the signal with the impulse function at time delays equal to n*1/fs. Am i on the right track????

    for the ssecond part. I couldn't even understand wat is it asking for????