1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Digital FIR Filter Design

  1. Jun 2, 2009 #1
    I have a question which is to design a filter of the form:

    y(n) = a(0)x(n) + a(1)x(n-1) + a(2)x(n-2) to remove a narrowband disturbance with frequency f0 = 70Hz.
    The sampling frequency, fs is 280Hz.

    I've made an attempt at answering it, but don't think my result is correct:

    w0 = (2*pi)* (f0/fs) = pi/2

    I then calculate the zeros of the filter from the definition of w

    z1 = exp(i*(pi/2))[
    z2 = exp(-i*(pi/z))
    where i = sqrt(-1)

    The transfer function of the filter is therefore;

    Z2H(z) = (z - exp(i*(pi/2))[ )(z - exp(-i*(pi/z)) )

    When expanded and simplified this gives

    H(z) = z2 + 1, so the filter function

    y(n) = x(n) + x(n - 2),
    giving
    a(0) = 1
    a(1) = 0
    a(2) = 1

    Which I'm pretty sure is wrong. Can anyone tell me where I have gone wrong?
     
  2. jcsd
  3. Dec 22, 2009 #2
    You did wrong while expanding and simplifying
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook