A question about the freqz function

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Robert
Robert 2011-5-29
Hi,
My name is Robert and I´m having a minor problem with the freqz function in MATLAB. I´m using it to get the frequency response from a filter in the following way:
H=freqz(zeros,poles,frequency vector,sampling frequency)
however, when I plot the phase in the following way:
plot(180/pi*angle(H))
I don´t get the same phase characteristics as i get if i just write
freqz(zeros,poles,512,sampling frequency)
how do I get the same phase characteristics?
Thanks in advance Sincerely Robert
  2 个评论
Walter Roberson
Walter Roberson 2011-5-29
I am not familiar with that function, but I wonder if perhaps you should unwrap() the angle(H) ?
Robert
Robert 2011-5-30
That solved the problem:)
If I write:
plot(180/pi*unwrap(angle(H)))
The characteristics is as it should be.
Thank you so much!

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回答（1 个）

Paulo Silva
Paulo Silva 2011-5-29
Try this way:
[h,w]=freqz(zeros,poles,frequency vector,sampling frequency)
plot(frequency vector,w)

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