Code for PWM (Pulse Width Modulation) generation in MATLAB

PWM (Pulse Width Modulation) can be easily generated in MATLAB using simple MATLAB functions. We have already discussed about PWM generator circuit using 741 Op-amp in previous posts. In PWM, width of the pulses are varied according to the amplitude of AF message signal. PWM is basically an analog pulse modulation technique. It does modulation of the duty cycle of the pulse.
In addition to its use in communication systems, PWM is also used in voltage regulators such as Switched Mode Power Supplies (SMPS) to control the power delivered to the load. PWM can be generated using a comparator to which the modulating signal and a reference ramp (sawtooth) waveform are fed.

The code for PWM simulation in MATLAB is shown below. The use of particular line of MATLAB code is also given as comments (%Comment field). The given MATLAB program accepts two input frequencies from the user.

PWM MATLAB Codes

clc;

clear all;

close all;

F2=input('Message frequency=');

F1=input('Carrier Sawtooth frequency=');

A=5;

t=0:0.001:1;

c=A.*sawtooth(2*pi*F1*t);%Carrier sawtooth

subplot(3,1,1);

plot(t,c);

xlabel('time');

ylabel('Amplitude');

title('Carrier sawtooth wave');

grid on;

m=0.75*A.*sin(2*pi*F2*t);%Message amplitude must be less than Sawtooth

subplot(3,1,2);

plot(t,m);

xlabel('Time');

ylabel('Amplitude');

title('Message Signal');

grid on;

n=length(c);%Length of carrier sawtooth is stored to 'n'

for i=1:n%Comparing Message and Sawtooth amplitudes

if (m(i)>=c(i))

    pwm(i)=1;

else

    pwm(i)=0;

end

end

subplot(3,1,3);

plot(t,pwm);

xlabel('Time');

ylabel('Amplitude');

title('plot of PWM');

axis([0 1 0 2]);%X-Axis varies from 0 to 1 & Y-Axis from 0 to 2

grid on;

Generated PWM Signal

Inputs and Observation: 
 Message frequency=1
Carrier Saw tooth frequency=10

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