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MATLAB Code for Constellation Diagrams of ASK, FSK, and PSK

 

MATLAB Script

% The code is developed by SalimWireless.Com

clc;

clear;

close all;


% Parameters

numSymbols = 1000; % Number of symbols to simulate

symbolIndices = randi([0 1], numSymbols, 1); % Random binary symbols (0 or 1)


% ASK Modulation (BASK)

askAmplitude = [0, 1]; % Amplitudes for binary ASK

askSymbols = askAmplitude(symbolIndices + 1); % Modulated BASK symbols


% FSK Modulation (Modified BFSK with 90-degree offset)

fs = 100; % Sampling frequency

symbolDuration = 1; % Symbol duration in seconds

t = linspace(0, symbolDuration, fs*symbolDuration);

fBase = 1; % Base frequency

frequencies = [fBase, fBase]; % Same frequency for both


% Generate FSK symbols with 90° phase offset

fskSymbols = arrayfun(@(idx) ...

    cos(2*pi*frequencies(1)*t) * (1-idx) + ...

    1j * cos(2*pi*frequencies(2)*t) * idx, ...

    symbolIndices, 'UniformOutput', false);


% Extract last points (constellation points)

fskConstellation = cellfun(@(x) x(end), fskSymbols);


% PSK Modulation (BPSK)

pskSymbols = exp(1j * pi * symbolIndices); % Binary PSK symbols in complex plane


% Plotting

figure;


% ASK Constellation Diagram

subplot(1, 3, 1);

scatter(real(askSymbols), zeros(size(askSymbols)), 'filled');

grid on;

title('Binary ASK (BASK) Constellation');

xlabel('In-phase');

ylabel('Quadrature');

axis([-1.5 1.5 -1.5 1.5]);


% FSK Constellation Diagram

subplot(1, 3, 2);

scatter(real(fskConstellation), imag(fskConstellation), 'filled');

grid on;

title('Binary FSK (BFSK) Constellation with 90° Offset');

xlabel('In-phase');

ylabel('Quadrature');

axis([-1.5 1.5 -1.5 1.5]);


% PSK Constellation Diagram

subplot(1, 3, 3);

scatter(real(pskSymbols), imag(pskSymbols), 'filled');

grid on;

title('Binary PSK (BPSK) Constellation');

xlabel('In-phase');

ylabel('Quadrature');

axis([-1.5 1.5 -1.5 1.5]);


Output






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