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MATLAB Code for Pulse Amplitude Modulation (PAM) and Demodulation

 

Pulse Amplitude Modulation (PAM) & Demodulation

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');

 

 Output

 

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Another Code for Pulse Amplitude Modulation

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');

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);

Output






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