I need to plot a phase response using freqz function. Can you please help with it.

system was given h[n]

I obtained the frequency response and the phase below. when i plotted it did not look right.

Can please help me to plot it using the freqz command.

angle(H(e^jw)= tan ^-1(sin(w)-2*sin(w)+4*sin(3*w)-4*sin(5*w)+3sin(6*w)-2*sin(7*w)+sin(8*w))/(1-2*cos(w)+3*cos(2*w)-4*cos(3*w)+4*cos(5*w)-3*cos(6*w)+2*cos(7*w)-8*cos(8*w)

Answer 1

[Geetla Sindhu]

Hello Gerald,

I understand that you are trying to plot the phase of the frequency response of the system using “freqz” command.

You can try the following workaround to solve the issue:

• If the system transfer function is given in the form of

Use

     [H,w] = freqz(B,A,n,fs)

where, B = [b(1) b(2) … b(M)]

A = [a(1) a(2) … a(N)]

fs = Sampling rate

Please refer to Frequency response of digital filter - MATLAB freqz(mathworks.com) for further information regarding "freqz" command.

• In order to get the phase response of the system in degrees, use

     plot(w,angle(H)*360/(2*pi))

You can also refer to the example below for reference:

• Phase-plot when using freqz - MATLAB Answers - MATLAB Central (mathworks.com)

Thank you.