MATLAB Code for ASK, FSK, and PSK

MATLAB Code for Amplitude Shift Keying (ASK)

% The code is written by SalimWireless.Com 
% Clear previous data and plots
clc; 
clear all; 
close all;

% Parameters
Tb = 1;             % Bit duration
fc = 10;            % Carrier frequency
N = 10;             % Number of bits

% Generate carrier signal
t = 0:Tb/100:1;
carrier_signal = sqrt(2/Tb) * sin(2*pi*fc*t);

% Generate message signal
rng(10);            % Set random seed for reproducibility
binary_data = rand(1, N);  % Generate random binary data
t_start = 0; t_end = Tb;

for i = 1:N 
    t = [t_start:0.01:t_end]; 
    
    % Generate message signal
    if binary_data(i) > 0.5 
        binary_data(i) = 1; 
        message_signal = ones(1, length(t)); 
    else 
        binary_data(i) = 0; 
        message_signal = zeros(1, length(t)); 
    end 
    
    % Store message signal
    message(i,:) = message_signal; 
    
    % Modulate message with carrier
    ask_signal(i,:) = carrier_signal .* message_signal; 
    
    % Update time intervals
    t_start = t_start + (Tb + 0.01); 
    t_end = t_end + (Tb + 0.01); 
    
    % Plot message and ASK signal
    subplot(5,1,2); 
    axis([0 N -2 2]);
    plot(t, message(i,:), 'r'); 
    title('Message Signal');
    xlabel('t --->');
    ylabel('m(t)');
    hold on; 
    
    subplot(5,1,4);
    plot(t, ask_signal(i,:));
    title('ASK Signal');
    xlabel('t --->');
    ylabel('s(t)');
    hold on; 
    
    % Plot carrier signal
    subplot(5,1,3);
    plot(t, carrier_signal);
    title('Carrier Signal');
    xlabel('t --->');
    ylabel('c(t)');
    hold on; 
end

hold off;

% Plot binary data bits
subplot(5,1,1);
stem(binary_data);
title('Binary Data Bits');
xlabel('n --->');
ylabel('b(n)');
grid on;

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% ASK Demodulation %%%%%%%%%%%%%%%%%%
t_start = 0; t_end = Tb;
for i = 1:N 
    t = [t_start:Tb/100:t_end]; 
    
    % Correlator
    correlation = sum(carrier_signal .* ask_signal(i,:)); 
    
    % Decision device
    if correlation > 0 
        demodulated_data(i) = 1; 
    else 
        demodulated_data(i) = 0; 
    end 
    
    % Update time intervals
    t_start = t_start + (Tb + 0.01); 
    t_end = t_end + (Tb + 0.01); 
end

% Plot demodulated binary data bits 
figure;
subplot(5,1,5);
stem(demodulated_data);
title('ASK Demodulated Signal');
xlabel('n --->');
ylabel('b(n)');
grid on;

Output

Fig 1: MATLAB Code for ASK Modulation and Demodulation

MATLAB Code for Frequency Shift Keying (FSK) and Demodulation

% The code is written by SalimWireless.Com 
% Clear the workspace, command window, and close all figures
clc; clear; close all;

% Parameters
Fs = 1000;          % Sampling frequency
fc1 = 1;            % Carrier frequency for bit 0
fc2 = 10;           % Carrier frequency for bit 1
Tb = 2;             % Duration of each bit in seconds
num_bits = 10;      % Number of bits

% Generate random bits
bits = randi([0, 1], 1, num_bits);

% FSK modulation
t = 0:1/Fs:Tb-1/Fs; % Time vector for one bit
modulated_signal = []; % Empty array for modulated signal

% Modulating each bit
for bit = bits
    if bit == 0
        modulated_signal = [modulated_signal sin(2*pi*fc1*t)]; % Modulate with carrier frequency fc1 for bit 0
    else
        modulated_signal = [modulated_signal sin(2*pi*fc2*t)]; % Modulate with carrier frequency fc2 for bit 1
    end
end

% Plot original signal
figure;
stem(bits, 'filled', 'LineStyle', 'none', 'Marker', 'o', 'Color', 'b', 'DisplayName', 'Original Bits');
hold on;
stem(bits, 'filled', 'LineStyle', 'none', 'Marker', 'x', 'Color', 'r', 'DisplayName', 'Demodulated Bits');
title('Original Information Bits');
xlabel('Bit Index');
ylabel('Bit Value');
legend;

% Plot modulated signal
figure;
plot(modulated_signal);
title('FSK Modulated Signal');
xlabel('Time');
ylabel('Amplitude');

% FSK demodulation
demodulated_signal = []; % Empty array for demodulated signal

% Demodulating each bit
for i = 1:length(modulated_signal)/length(t)
    segment = modulated_signal((i-1)*length(t)+1:i*length(t)); % Extract one bit duration segment
    % Compute correlation with carriers
    cor1 = abs(sum(segment.*sin(2*pi*fc1*t)));
    cor2 = abs(sum(segment.*sin(2*pi*fc2*t)));
    % Compare correlations to determine demodulated bit
    if cor1 > cor2
        demodulated_signal = [demodulated_signal 0];
    else
        demodulated_signal = [demodulated_signal 1];
    end
end

% Plot original and demodulated signals
figure;
stem(bits, 'filled', 'LineStyle', 'none', 'Marker', 'o', 'Color', 'b', 'DisplayName', 'Original Bits');
hold on;
stem(demodulated_signal, 'filled', 'LineStyle', 'none', 'Marker', 'x', 'Color', 'r', 'DisplayName', 'Demodulated Bits');
title('Original vs. Demodulated Bits');
xlabel('Bit Index');
ylabel('Bit Value');
legend;

Output

Fig 2: FSK Modulation and Demodulation

MATLAB Code for Phase Shift Keying (PSK)

Output

Fig 3: Phase Shift Keying (PSK)