Comparing spectra of periodic signals

Discussion in 'Homework Help' started by hshahid, Oct 29, 2012.

  1. hshahid

    Thread Starter New Member

    Oct 29, 2012
    Hi. I have a question for my homework that I'm having trouble with. If someone could point me in the right direction, I'd be very grateful! Here is the problem statement:

    x(n) is a periodic sequence with period N. We use it to make two finite sequences of length 2N:

    x1(n) = 'x(n) for 0 <= n < N' and '0 for N <= n < 2N'
    and x2(n) = 'x(n) for 0 <= n < 2N'

    Explain whether and how their spectra X(k), X1(k) and X2(k) are different?

    From what i can think of (and admittedly I'm not good at this) both x1 and x2 will have the same spectrum as x. x1 is x with zeros padded for another N samples and x2 is a double period of x. I'm way off the mark here, aren't I?