Hi Song,
As per my understanding, you want to specify the phase frequency of the target in the fresp function.
In MATLAB, you can specify the desired phase-frequency characteristics of the target response using the ‘fresp’ argument in “cfirpm” function. The ‘fresp’ argument can be a vector or a function handle. To specify the phase-frequency characteristics using the ‘fresp’ function we need to define a function that computes the desired phase at each frequency point.
In the below code, I have used quadratic phase function f^2 as an example. We can choose any phase function. Now, “cfirmp” function will design a filter that approximately matches the desired complex frequency response at the frequency of f.
Here is the sample code for reference:
n = 64; % Filter order
f = linspace(0, 1, 1000); % Frequency vector (0 to 1)
% Define the desired phase function
phase_function = @(f) 2*pi*f.^2; % Example: Quadratic phase
% Compute the desired complex frequency response using the phase function
desired_response = exp(1j*phase_function(f));
% Design the filter using cfirpm
b = cfirpm(n, f, desired_response);
disp(b);
For further reference, please check out the links to learn more about cfirpm function.
I hope this resolves the issue you were facing.
