Matlab DSP Difference equation and invert Biquad?

Discussion in 'Homework Help' started by Andyfreqz, Dec 19, 2010.

  1. Andyfreqz

    Thread Starter New Member

    Dec 19, 2010
    Hi, i have done an awfull lot of my assignment but am stuck on a few things, i have to randomly choose to poles and zeros on a zplane of a biquad iir filter. I was just wondering how the difference equation should be calculated manually? I have used [b,a] = zp2tf (z,p,1); to calculate the a and b coefficients for the difference equation and used freqz to plot the frequency response, i was just wondering how one would do this manually?

    Also the only other bit i am stuck on is how to invert the BiQuad? Do i just use the same m file and add inverted zeros and poles to it?

    Any help is appreciated thanks! If any more information is needed i can provide that also!
  2. guitarguy12387

    Active Member

    Apr 10, 2008
    Typically you do pole/zero design in the frequency domain. So you'd choose your poles and zeros and derive your transfer function from those locations. Then take the inverse z transform to find the difference equation.

    Is that what you are asking?

    I am not familiar with this. What do you mean 'invert' the biquad? What purpose would this serve?
  3. shteii01

    AAC Fanatic!

    Feb 19, 2010
    Here is example from my DSP class.