MATLAB Code for ASK, FSK, and PSK (with Online Simulator)

MATLAB Code for ASK, FSK, and PSK

Comprehensive implementation of digital modulation and demodulation techniques with simulation results.

📘 Theory 📡 ASK Code 📶 FSK Code 🎚️ PSK Code 🕹️ Simulator 📚 Further Reading

Amplitude Shift Frequency Shift Phase Shift Live Simulator

• ASK, FSK & PSK HomePage
• MATLAB Code

MATLAB Code for ASK Modulation and Demodulation

% The code is written by SalimWireless.Com clc; clear all; close all; % Parameters Tb = 1; fc = 10; N_bits = 10; Fs = 100 * fc; Ts = 1/Fs; samples_per_bit = Fs * Tb; rng(10); binary_data = randi([0, 1], 1, N_bits); t_overall = 0:Ts:(N_bits * Tb) - Ts; message_signal_overall = zeros(1, length(t_overall)); ask_signal_overall = zeros(1, length(t_overall)); carrier_template = sqrt(2/Tb) * sin(2*pi*fc*(0:Ts:Tb-Ts)); for i = 1:N_bits current_bit = binary_data(i); t_segment_indices = ((i-1)*samples_per_bit + 1) : (i*samples_per_bit); if current_bit == 1 message_segment = ones(1, samples_per_bit); else message_segment = zeros(1, samples_per_bit); end ask_segment = carrier_template .* message_segment; message_signal_overall(t_segment_indices) = message_segment; ask_signal_overall(t_segment_indices) = ask_segment; end

Fig 1: ASK Modulation and Demodulation

MATLAB Code for FSK Modulation and Demodulation

% The code is written by SalimWireless.Com clc; clear; close all; % Parameters Fs = 1000; fc1 = 20; fc2 = 50; Tb = 1; num_bits = 10; Ts = 1/Fs; samples_per_bit = Fs * Tb; rng(20); bits = randi([0, 1], 1, num_bits); t_bit = 0:Ts:Tb-Ts; modulated_signal = []; for bit = bits if bit == 0 modulated_signal = [modulated_signal sin(2*pi*fc1*t_bit)]; else modulated_signal = [modulated_signal sin(2*pi*fc2*t_bit)]; end end

Fig 2: FSK Modulation and Demodulation

MATLAB Code for PSK Modulation and Demodulation

% The code is written by SalimWireless.Com clc; clear all; close all; carrier_frequency = 10; bit_duration = 1; sampling_frequency = 1000; Ts = 1/sampling_frequency; samples_per_bit = sampling_frequency * bit_duration; rng(30); bit_stream = randi([0, 1], 1, 8); t_bit = 0:Ts:bit_duration-Ts; psk_signal = []; for bit = bit_stream if bit == 0 psk_signal = [psk_signal sin(2*pi*carrier_frequency*t_bit + 0)]; else psk_signal = [psk_signal sin(2*pi*carrier_frequency*t_bit + pi)]; end end

Fig 3: PSK Modulation and Demodulation

Understanding the MATLAB Implementation

Key Variables

• Fs: Sampling frequency (must be > 2x carrier frequency).
• Tb: Bit duration (defines how long each symbol lasts).
• rng(10): Ensures your random bit generation is reproducible.

The Logic

The code uses a for loop to iterate through the bitstream. Depending on the bit value (0 or 1), it selects the appropriate carrier frequency or phase, effectively performing Hard-Decision Mapping.

Common MATLAB Errors & Fixes

1. "Undefined function or variable": Ensure you are running the script in the same folder where your variables are saved. Use clc; clear all; at the top.

2. Aliasing in Plots: If your waveforms look "jagged," increase the Fs (Sampling Frequency) to at least 10 times the carrier frequency.

3. Toolboxes: These codes run on base MATLAB, but for advanced BER analysis, you may need the Communication Toolbox.

Interactive Modulation Simulator

Launch the web-based tool to simulate digital modulation techniques.

Launch Simulator →

Modulation	Parameter Changed	Noise Immunity	Complexity
ASK	Amplitude	Low (Highly susceptible)	Simplest
FSK	Frequency	High (Robust)	Moderate
PSK	Phase	Very High	Highest (Requires Coherent Detection)

From Simulation to Hardware

While these MATLAB scripts simulate digital modulation in a vacuum, real-world deployment requires considering AWGN (Additive White Gaussian Noise). If you are moving to hardware like USRP (Universal Software Radio Peripheral) or RTL-SDR, you must implement Pulse Shaping (like Root-Raised Cosine) to limit bandwidth occupancy. Want to read more about raised cosine filter? Click here.

Frequently Asked Questions

Which is better: ASK, FSK, or PSK?

PSK is generally superior for high-speed data because it is the most bandwidth-efficient and noise-resistant, though it requires more complex receiver hardware.

How do I calculate BER in MATLAB?

You can use the biterr function in MATLAB to compare the transmitted bitstream with the demodulated bitstream to calculate the Bit Error Rate.

📚 Further Reading

• 🔗 Simulation of ASK, FSK, and PSK using MATLAB Simulink
• 🔗 MATLAB Code for Constellation Diagrams
• 🔗 BER vs. SNR for ASK, FSK, and PSK

BER vs SNR Main Page > Modulation Techniques Main Page >
DSP Simulations Main Page >