Question about adding frequency/phase offsets into code for a synchronous demodulator

Hi. I was just wondering how would I add a frequency and phase offset into my current code. I want to compare the two, but understand that I can only run one at a time as they're part of the same command.

But basically I just want to be able to first run 4 lots of frequency offsets, then run 4 lots of phase offsets from 0 to 360 to compare the results, but I'm not exactly sure how to do so. Any help would be appreciated. I have left my full code below also.

I'm wanting to run the code at a modulation depth of infinity for the synchronous demodulator using a non-coherent local oscillator in the demodulator, which has the frequency/phase offsets to change, so I'm only going to be looking at/analyzing the demodulated signal.

% Synchronous Modulator/Demodulator
% MATLAB script for Illustrative Problem 3.5.
% script for DSB-AM synchronous demodulation. The message signal
% is +1 for 0 < t < t0/3, -2 for t0/3 < t < 2t0/3, and zero otherwise.
% message is also cosine at 20Hz with Vm=1;
% a is the modulation index and can be varied
close all
clear all
clc
%%echo on
t0=.75;                                 % signal duration
ts=1/1500;                           % sampling interval
fm=50;                                 % message signal frequency
fc=4;                                    % carrier frequency
a=1;                              	    % Modulation index a = amplitude of message/ amplitude of carrier
fs=1/ts;                                % sampling frequency
t=[0:ts:t0];                            % time vector
df=0.3;                                 % desired frequency resolution
% message signal
m=[ones(1,t0/(3*ts)),-2*ones(1,t0/(3*ts)),zeros(1,t0/(3*ts)+1)];
m=cos(2*pi*fm.*t);
c=cos(2*pi*fc.*t);                      % carrier signal
u=m.*c;                                 % modulated signal
m_n=m/max(abs(m));                   	  % normalized message signal
u=(1+a*m_n).*c;                      	  % modulated signal

%received signal
y=u.*c;                                 % mixing
%Local oscillator - change the frequency and phase of c by desired values
[M,m,df1]=fftseq(m,ts,df);              % Fourier transform
M=M/fs;                                 % scaling
[U,u,df1]=fftseq(u,ts,df);              % Fourier transform
U=U/fs;                                 % scaling
[Y,y,df1]=fftseq(y,ts,df);              % Fourier transform
Y=Y/fs;                                 % scaling
f_cutoff=150;                           % cutoff freq. of the filter
n_cutoff=floor(150/df1);                % Design the filter.
f=[0:df1:df1*(length(y)-1)]-fs/2;
H=zeros(size(f));
H(1:n_cutoff)=2*ones(1,n_cutoff);
H(length(f)-n_cutoff+1:length(f))=2*ones(1,n_cutoff);
DEM=H.*Y;                   % spectrum of the filter output
dem=real(ifft(DEM))*fs;             % filter output
% the effect of mixing.
figure(1);
subplot(3,1,1)
plot(m(1:length(t)))
title('Waveform of the Message Signal')
xlabel('Time')
subplot(3,1,2)
plot(u(1:length(t)))
title('Waveform of the Modulated Signal')
xlabel('Time')
subplot(3,1,3)
plot(y(1:length(t)))
title('Waveform of the Mixer Output')
xlabel('Time')
figure(2);
subplot(3,1,1)
plot(f,fftshift(abs(M)))
title('Spectrum of the Message Signal')
xlabel('Frequency')
subplot(3,1,2)
plot(f,fftshift(abs(U)))
title('Spectrum of the Modulated Signal')
xlabel('Frequency')
subplot(3,1,3)
plot(f,fftshift(abs(Y)))
title('Spectrum of the Mixer Output')
xlabel('Frequency')
% the effect of filtering on the mixer output.
figure(3);
subplot(3,1,1)
plot(f,fftshift(abs(Y)))
title('Spectrum of the Mixer Output')
xlabel('Frequency')
subplot(3,1,2)
plot(f,fftshift(abs(H)))
title('Lowpass Filter Characteristics')
xlabel('Frequency')
subplot(3,1,3)
plot(f,fftshift(abs(DEM)))
title('Spectrum of the Demodulator output')
xlabel('Frequency')
% to compare the spectra of the message and the received signal.
figure(4);
subplot(2,1,1)
plot(f,fftshift(abs(M)))
title('Spectrum of the Message Signal')
xlabel('Frequency')
subplot(2,1,2)
plot(f,fftshift(abs(DEM)))
title('Spectrum of the Demodulator Output')
xlabel('Frequency')
% the message and the demodulator output signals.
figure(5);
pfo = comm.PhaseFrequencyOffset('PhaseOffset',270);
subplot(2,1,1)
plot(t,m(1:length(t)))
title('The Message Signal')
xlabel('Time')
subplot(2,1,2)
plot(t,dem(1:length(t)))
title('The Demodulator Output')
xlabel('Time')

[Meck]

For some reason the post got editted so ill say this as a answer reply to my post.

This post can be ignored as I didnt notice the phase/freq offset added into the demodulated graph. With it present all I need to do is change the name to frequency or phase along with the value to run and ill be set.

[Craig EDWARDS]

Hi meck, I’m having trouble with the same issue. How did you solve this?