frodonet
Posts:
5
From:
malaysia
Registered:
10/24/10


Re: [Matlab Question] Converting H(s) to H(z) using derivative approximation?
Posted:
Oct 24, 2010 3:11 PM


Hi Nasser,
thanks for your help.
Sorry i didn't post my workings before. Here is what i actually did in my matlab.
1) I found out the sroots by using the roots(p) command.
2) then i use the relationship for derivate approximation where z^1 = 1  sT.
3) So from s roots, i get the z roots and then i contruct the polynomial from zroots using the poly(A) command.
4) Then from the polynomial coefficients, i just use freqz to plot the magnitude vs freq response.
Not sure it's 100% right, but when i plot it the shape is correct which is a low pass filter but the magnitude might be a little off.
After seeing your solution, i need to give it a try.
But do you know that the relationship between s and z is as such :
z^1 = 1  sT
So when you have such relationship, does your method still holds?

