conv function to compute h[n]

Discussion in 'Programmer's Corner' started by angelita, Nov 30, 2010.

  1. angelita

    Thread Starter Member

    May 29, 2009
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    using conv function
    find : h[n] for the following

    y[n+2]-4y[n+1]+4y[n]=2x[n+2]-2x[n+1]
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
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    You first. ;)
     
  3. angelita

    Thread Starter Member

    May 29, 2009
    25
    0
    i asked for help bcoz i have no idea how to solve it
     
  4. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    Oh, Im sorry, I didn't see where you asked for help.

    It looked like you just told us to solve it.

    Is this a homework problem?

    What do you know so far about it?
     
  5. angelita

    Thread Starter Member

    May 29, 2009
    25
    0
    i used the conv function with values of h and x to find the convolution

    but i dont know how to de the reverse
     
  6. steveb

    Senior Member

    Jul 3, 2008
    2,433
    469
    Have you learned about z-transforms yet? This problem is straightforward in the frequency domain. If you have been taught z-transforms, we can guide you through the process which begins by taking the z-transform of your difference equation and then solving for H(z)=Y(z)/X(z). Then you take the inverse z-transform (using partial fraction expansion and a transform table) to work back to the impulse response funtion h[n].

    It's a little trickier to work it out in the discrete time domain because the system is unstable and the impulse response continues to increase to infinity. Hence, you need to work out a recursion equation to get a closed form. This can also be done, but I only recommend this approach if you haven't been taught z-transforms yet.
     
    Last edited: Nov 30, 2010
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