A question about the freqz function

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

[Walter Roberson]

I am not familiar with that function, but I wonder if perhaps you should unwrap() the angle(H) ?

[Robert]

That solved the problem:)

If I write:

plot(180/pi*unwrap(angle(H)))

The characteristics is as it should be.

Thank you so much!

Answer 1

[Paulo Silva]

Try this way:

[h,w]=freqz(zeros,poles,frequency vector,sampling frequency)
plot(frequency vector,w)