MATLAB Code for Pulse Amplitude Modulation (PAM) and Demodulation

Pulse Amplitude Modulation (PAM) & Demodulation

• 📘 Overview & Theory of Pulse Amplitude Modulation (PAM)
• 🧮 MATLAB Code for Pulse Amplitude Modulation and Demodulation of Analog Signal and Digital Signal
• 🧮 Simulation Results for Comparison of PAM, PWM, PPM, DM, and PCM
• 📚 Further Reading

• 🧮 MATLAB Code for Pulse Amplitude Modulation and Demodulation of an Analog Signal (2)
• 🧮 MATLAB Code for Pulse Amplitude Modulation and Demodulation of Digital Data
• 🧮 Other Pulse Modulation Techniques (PWM, PPM, DM, PCM)

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; % sampling frequency (100 kHz)
t = 0:1/fs:1;
m = 1 * cos(2 * pi * fm * t);
c = 0.5 * square(2 * pi * fc * t) + 0.5;
s = m .* c;

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');

% Demodulation
d = s .* c;
filter = fir1(200,fm/fs,'low');
original_t_signal = conv(filter,d);
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

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

MATLAB Script

clc;
clear;
close all;

% Parameters
messageFrequency = 2;
carrierFrequency = 20;
samplingFrequency = 1000;
duration = 1;
A = 1;

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

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

% Carrier signal
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');
subplot(3,1,2); plot(t, carrierSignal); title('Carrier Signal');
subplot(3,1,3); plot(t, pamSignal); title('PAM Signal');

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

Pulse Amplitude Modulation (PAM) & Demodulation for Digital Data

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

% Parameters
M = 8;
numSymbols = 100;
Fs = 1000;
T = 1;

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

% PAM Modulation
pamLevels = linspace(-M + 1, M - 1, M);
modulatedSignal = pamLevels(data + 1);

% Create 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 noise
snr = 20;
noisySignal = awgn(upsampledSignal, snr, 'measured');

% PAM Demodulation
receivedSymbols = noisySignal(1:Fs:end);
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');
subplot(4,1,2); plot(t, upsampledSignal); title('Transmitted PAM Signal');
subplot(4,1,3); plot(t, noisySignal); title('Received Noisy PAM Signal');
subplot(4,1,4); stem(demodulatedData); title('Demodulated Data');
grid on;

disp('Original Data:'); disp(data);
disp('Demodulated Data:'); disp(demodulatedData);

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

Output

Parameter	PAM	PWM	PPM	DM	PCM
What is varied?	Amplitude	Width	Position	Delta (difference)	Binary code
Pulse Width	Constant	Variable	Constant	Constant	Constant
Noise Immunity	Low	Moderate	High	Moderate	High
Bandwidth	Low	Medium	High	Low	High
Complexity	Simple	Moderate	Complex	Simple	Complex
MATLAB Code	PAM Script	PWM Script	PPM Script	DM Script	PCM Script
Detailed Study	PAM	PWM	PPM	DM	PCM

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

PWM | PPM | DM | Quantization | PCM

Explore Signal Processing Simulations

Simulator Setup PAM Modulation Demodulation

Instructions for Pulse Amplitude Modulation (PAM)

• Note: Use the input fields to enter the message frequency and the square pulse carrier frequency.
• Step 1: Click the "Generate Message" button to generate the input message signal.
• Step 2: Click the "Generate Carrier" button to generate the carrier signal. Carrier must be > Message.
• Step 3: Click the "Generate PAM Signal" button to generate the Modulated signal.

Message Frequency (Hz):

Square Carrier Frequency (Hz):

Simulation Control:

PAM Modulation Control Center

Perform Pulse Amplitude Modulation by interacting with the signal generators below.

Ready for Signal Recovery?

After generating your PAM signal, proceed to the Demodulation section to recover the original message using a reconstruction filter.

Go to Demodulation

Instructions for Pulse Amplitude Demodulation

• The reconstruction filter recovers the original message from the sampled PAM signal.
• A low-pass filter (LPF) is used with a cutoff frequency at or above the message frequency.
• Click 'Demodulate' to view the recovered baseband signal.

Cut-off Frequency (Hz)

Technical Definition: PAM Signal

MATLAB Mathematical Representation Copy Snippet

% Ideal Sampling with Pulse Train t = 0:0.001:1; fm = 2; fc = 10; m_t = cos(2*pi*fm*t); c_t = square(2*pi*fc*t); s_pam = m_t .* (c_t > 0); % Low Pass Reconstruction [b,a] = butter(4, fm/(fs/2)); demod = filter(b,a, s_pam);

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