SSB signal modulation and demodulation based on MATLAB (with source code)

For detailed principles, please refer to the course design report ： be based on matlab Of SSB signal modulation 、 transmission 、 Simulation of demodulation - Industry report document resources -CSDN download

The modulation adopts filtering method and phase shift method .
There are comments in the code , No subfunction , It can run directly .
The compressed package contains a specific lesson design report , There is a detailed description of the principle , Run a screenshot 、 Result analysis, etc .

matlab The code and running results are as follows ：

% Signal parameter setting
% Set the baseband signal to 100Hz, The carrier signal is 1kHz
fm=100;fc=10^3;    % signal frequency fm, Carrier frequency fc
Fs=10^4;     % sampling frequency Fs
wc=2*pi*fc;
wm=2*pi*fm;
T = 1/Fs; % Sampling interval
L=2*10^4; % Signal length
t = (0:L-1)*T ; 
f = Fs*(0:(L/2))/L;

% Baseband signal time domain
sm=cos(wm*t);
figure('Name',' baseband signal ');
subplot(211);
plot(t,sm);
title(' Baseband signal time domain ');
xlabel('t');
axis([0 1 -2 2]);
grid on

% Baseband signal frequency domain
S1=fft(sm);
P1b=abs(S1/L);
% Get unilateral
P1a = P1b(1:L/2+1);
P1a(2:end-1) = 2*P1a(2:end-1);
subplot(212);
plot(f,P1a);      %SSB Signal frequency domain waveform
xlabel('Frequency(HZ)');
title(' Baseband signal frequency domain waveform ');
axis([0 150 0 1])
grid on;

% carrier signal
sc=cos(wc*t);
figure('Name',' carrier signal ');
subplot(211);
plot(t,sc);
title(' Carrier signal time domain ');
xlabel('t');
axis([0 1 -2 2]);
grid on
% frequency domain
Sc=fft(sc);
Pcb=abs(Sc/L);
% Get unilateral
Pca = Pcb(1:L/2+1);
Pca(2:end-1) = 2*Pca(2:end-1);
subplot(212);
plot(f,Pca);      % Frequency domain waveform
xlabel('Frequency(HZ)');
title(' Frequency domain waveform of carrier signal ');
axis([500 1500 0 1])
grid on;

% modulation
% Filtering
% Get one first DSB The signal , That is, the modulated signal is multiplied by the carrier signal
s2 = cos(wc*t).*sm;
% Frequency domain diagram
S2=fft(s2);
P2b=abs(S2/L);
% Get unilateral
P2a = P2b(1:L/2+1);
P2a(2:end-1) = 2*P2a(2:end-1);
figure('name',' Filtering '); 
subplot(211);
plot(f,P2a);      % The frequency domain waveform of the signal is modulated by filtering
title(' Generated DSB The signal ');
axis([850 1200 0 1])

% Low pass filtering
fp1=[800 1000];fs1=[700 1100];
Fs2=Fs/2;
Wp=fp1/Fs2; Ws=fs1/Fs2;
Rp=1; Rs=30;
[n,Wn]=cheb2ord(Wp,Ws,Rp,Rs);
[b1,a1]=cheby2(n,Rs,Wn);
s3=filter(b1,a1,s2);% after filter The data obtained after filtering y It is the signal data after band-pass filtering
% Frequency domain diagram
S3=fft(s3);
P3b=abs(S3/L);
% Get unilateral  
P3a = P3b(1:L/2+1);
P3a(2:end-1) = 2*P3a(2:end-1);
subplot(212);
plot(f,P3a);      % The frequency domain waveform of the signal is modulated by filtering
axis([850 1200 0 1])
title(' Low pass filtering becomes SSB The signal ') ;
grid on ;

% Phase shift method
%SSB Modulated signal frequency domain
figure('name',' Phase shift method ');
% Use
s4=modulate(sm,fc,Fs,'amssb')/2;       % Modulate the modulated signal
S4 = fft(s4);
P4b = abs(S4/L);
% Get unilateral  
P4a = P4b(1:L/2+1);
P4a(2:end-1) = 2*P4a(2:end-1);
plot(f,P4a);      % Frequency domain waveform of modulated signal by phase shift
axis([850 1200 0 1])
title(' Phase shift method generates SSB The signal ') ;
grid on;

% Analog transmission , Add noise to the signal , Embed the modulated signal with a variance of 0.1 In white Gaussian noise .
% Add noise to the signal
cur = size(s4); 
s5 = s4 + 0.5*randn(size(t));
S5=fft(s5);
P5b = abs(S5/L); 
P5a = P5b(1:L/2+1);
P5a(2:end-1) = 2*P5a(2:end-1);
figure('name',' transmission - Add noise ');
plot(f,P5a);     % Frequency domain waveform after noise
axis([500 1000 0 1])
xlabel('Frequency(HZ)');
title(' Noisy frequency domain waveform ');
grid on;

% Band pass filtering
% Bandpass range ：890~910Hz
fp1=[899,901];fs1=[890 905];
Fs2=Fs/2;
Wp=fp1/Fs2; Ws=fs1/Fs2;
Rp=1.1; Rs=10;
[n,Wn]=cheb2ord(Wp,Ws,Rp,Rs);
[b1,a1]=cheby2(n,Rs,Wn);
s6=filter(b1,a1,s5); % after filter The data obtained after filtering y It is the signal data after band-pass filtering
S6=fft(s6);
P6b = abs(S6/L); 
P6a = P6b(1:L/2+1);
P6a(2:end-1) = 2*P6a(2:end-1);
figure('name',' receive - Band pass filtering ')
plot(f,P6a);     % Frequency domain waveform after noise
axis([500 1000 0 1])
xlabel('Frequency(HZ)');
title(' Bandpass frequency domain waveform ');
grid on;

% demodulation
figure('name',' demodulation ');
subplot(211);
% Amplitude demodulation , Single sideband . multiply y Frequency sine curve and use ..fc Apply a fifth order Butterworth low-pass filter filtfilt
%{
x = y.*cos(2*pi*fc*t);
[b,a] = butter(5,fc*2/fs);
x = filtfilt(b,a,x);
%}
s7=demod(s6,fc,Fs,'amssb');         % Yes SSB Demodulate the signal
S7=fft(s7);
P7b = abs(S7/L); 
P7a = P7b(1:L/2+1);
P7a(2:end-1) = 2*P7a(2:end-1);
plot(f,P7a);     % Frequency domain waveform after demodulation
axis([0 110 0 1])
xlabel('Frequency(HZ)');
title(' Demodulate the frequency domain waveform ');
grid on;
subplot(212);
plot(t,s7);                              % Time domain waveform after demodulation
title(' Time domain waveform after demodulation ');
xlabel('t');
subplot(2,1,2);
axis([0 1 -2 2]);
grid on;

figure('name',' Compare modulation and demodulation ')
subplot(211) ; 
plot(t,sm);
title(' Baseband signal time domain ');
xlabel('t');
axis([0 1 -2 2]);
subplot(212);
plot(t,s7*4);                              % Time domain waveform after demodulation
title(' Time domain waveform after demodulation ');
xlabel('t');
axis([0 1 -2 2]);
grid on;

% Calculate system performance
%SSB_6(fm,sm)
disp(' Calculate system performance ')
%n0 = 5*10^-15    % Define the parameters of Gaussian white noise n0
% Calculate the system performance subfunction
syms n0
B = fm; % bandwidth
Ni = n0*B ;
No = 1/4*Ni; 
mo = 1/4*sm;
So = mean(mo.^2);
Si = 1/4*mean(sm.^2);
disp(' Input SNR ：')
ans1 = Si./Ni % Input SNR
disp(' Output signal to noise ratio :')
ans2 = So./No  % Output signal to noise ratio
disp(' Institutional gain ')
Gssb = ans2./ans1  % Institutional gain
 

Running results ：