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MATLAB Code for Pulse Amplitude Modulation (PAM) and Demodulation


 

Pulse Amplitude Modulation (PAM) & Demodulation of an Analog Message Signal

MATLAB Script

clc;

clear all;

close all;

fm= 10; % frequency of the message signal

fc= 100; % frequency of the carrier signal

fs=1000*fm; % (=100KHz) sampling frequency (where 1000 is the upsampling factor)

t=0:1/fs:1; % sampling rate of (1/fs = 100 kHz)

m=1*cos(2*pi*fm*t); % Message signal with period 2*pi*fm (sinusoidal wave signal)

c=0.5*square(2*pi*fc*t)+0.5; % square wave with period 2*pi*fc

s=m.*c; % modulated signal (multiplication of element by element)

subplot(4,1,1);

plot(t,m);

title('Message signal');

xlabel ('Time');

ylabel('Amplitude');

subplot(4,1,2);

plot(t,c);

title('Carrier signal');

xlabel('Time');

ylabel('Amplitude');

subplot(4,1,3);

plot(t,s);

title('Modulated signal');

xlabel('Time');

ylabel('Amplitude');

%demdulated

d=s.*c; % At receiver, received signal is multiplied by carrier signal

filter=fir1(200,fm/fs,'low'); % low-pass FIR filter which order is 200

% here fm is the cut-off frequency and the fs is the sampling frequency

original_t_signal=conv(filter,d); % convolution of demodulated signal with filter %coefficient

t1=0:1/(length(original_t_signal)-1):1;

subplot(4,1,4);

plot(t1,original_t_signal);

title('demodulated signal');

xlabel('time');

ylabel('amplitude');

web('https://www.salimwireless.com/search?q=pulse%20amplitude%20modulation', '-browser');

 Output

 

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Another Code for Pulse Amplitude Modulation and Demodulation of an Analog Message Signal 

MATLAB Script

 clc;
clear;
close all;

% Parameters
messageFrequency = 2;   % Message frequency in Hz
carrierFrequency = 20;  % Carrier frequency in Hz
samplingFrequency = 1000; % Sampling frequency in Hz
duration = 1;           % Signal duration in seconds
A = 1;                  % Amplitude of the signals

% Time vector
t = 0:1/samplingFrequency:duration;

% Message signal (sinusoidal)
messageSignal = A * sin(2 * pi * messageFrequency * t);

% Carrier signal (square wave)
carrierSignal = A * square(2 * pi * carrierFrequency * t);

% PAM signal
pamSignal = messageSignal .* (carrierSignal > 0);

% Plotting
figure;
subplot(3,1,1);
plot(t, messageSignal);
title('Message Signal');
xlabel('Time (s)');
ylabel('Amplitude');

subplot(3,1,2);
plot(t, carrierSignal);
title('Carrier Signal');
xlabel('Time (s)');
ylabel('Amplitude');

subplot(3,1,3);
plot(t, pamSignal);
title('PAM Signal');
xlabel('Time (s)');
ylabel('Amplitude');
web('https://www.salimwireless.com/search?q=pulse%20amplitude%20modulation', '-browser');

Copy the Code from here

 

Pulse Amplitude Modulation (PAM) & Demodulation for Digital Data

% The code is written by SalimWireless.Com
clc;
clear;
close all;


% PAM Modulation and Demodulation Example


% Parameters
M = 8; % PAM order (8-PAM)
numSymbols = 100; % Number of symbols to transmit
Fs = 1000; % Sampling frequency
T = 1; % Symbol duration


% Generate random data
data = randi([0 M-1], 1, numSymbols); % Random data symbols


% PAM Modulation
% Map the data symbols to PAM levels
pamLevels = linspace(-M + 1, M - 1, M); % PAM levels
modulatedSignal = pamLevels(data + 1); % Map data to PAM levels


% Create a time vector
t = 0:1/Fs:T*numSymbols-1/Fs;


% Upsample and create PAM signal
upsampledSignal = zeros(1, length(t));
for i = 1:numSymbols
upsampledSignal((i-1)*Fs+1:i*Fs) = modulatedSignal(i);
end


% Add some noise
snr = 20; % Signal-to-noise ratio
noisySignal = awgn(upsampledSignal, snr, 'measured');


% PAM Demodulation
% Sample the noisy signal at symbol rate
receivedSymbols = noisySignal(1:Fs:end);


% Map received symbols to nearest PAM level
demodulatedData = zeros(1, numSymbols);
for i = 1:numSymbols
[~, demodulatedData(i)] = min(abs(receivedSymbols(i) - pamLevels));
end


% Plotting
figure;
subplot(4,1,1);
stem(data);
title('Original Data');
xlabel('Time (s)');
ylabel('Amplitude');


subplot(4,1,2);
plot(t, upsampledSignal);
title('Transmitted PAM Signal');
xlabel('Time (s)');
ylabel('Amplitude');


subplot(4,1,3);
plot(t, noisySignal);
title('Received Noisy PAM Signal');
xlabel('Time (s)');
ylabel('Amplitude');


subplot(4,1,4);
stem(demodulatedData);
title('Demodulated Data');
xlabel('Symbol Index');
ylabel('PAM Level');
grid on;


% Display results
disp('Original Data:');
disp(data);
disp('Demodulated Data:');
disp(demodulatedData);
web('https://www.salimwireless.com/search?q=pulse%20amplitude%20modulation', '-browser');

Output






Copy the MATLAB Code from here



Simulation Results for comparison of PAM, PWM, PPM, DM, and PCM

 
 
 
 

 
  
 

 
 
 
 
 

 
 
 

Explore Signal Processing Simulations

Further Reading

  1. Pulse Amplitude Modulation and Demodulation theory
  2. Is PAM a Digital Modulation Technique ?
  3. Pulse Width Modulation (PWM) and Demodulation
  4. Pulse Position Modulation (PPM) and Demodulation
  5. Delta Modulation and demodulation
  6. Pulse Code Modulation (PCM)
  7. Quantization Signal to Noise Ration (Q-SNR)
  8. MATLAB Code for Pulse Width Modulation and Demodulation
  9. MATLAB Code for Pulse Position Modulation (PPM) and Demodulation
  10. MATLAB Code for Pulse Code Modulation (PCM) and demodulation

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