Plotting a square pulse periodic function

Hi,

could you please help me with the issue

I wrote a code to generate a periodic square pulse function. I am getting different output if i change the limits, which looks quite weird to me

here is my code and the output

the pulses start missing if i change the limits

clc

clear all

close all

syms t;

T=5;

x =@(t)piecewise((t-T*round(t/T))<-0.5,0,(t-T*round(t/T))>0.5,0,-0.5<=(t-T*round(t/T))<=0.5,1);

figure()

subplot(2,1,1)

fplot(t,x(t),[-21 21]);title('input signal x(t)');xlabel('time in s -->');ylabel('value');

subplot(2,1,2)

%Here I am just changing the limits of the x axis but getting different plot

fplot(t,x(t),[-25 25]);title('input signal x(t)');xlabel('time in s -->');ylabel('value');

Answer 1

[Star Strider]

I am not certain what you are doing, or what you want.

There are several ways to create square wave pulse trains. Probably the easiest is:

sqrwav = @(t,TL,f) sign(sin(2*pi*t*f)-TL);              % Create Square Wave, Threshold = TL, Frequency = f

t = linspace(0, 25, 500);
freq = 0.5;
ThrshLim = 0.9;

figure
plot(t, sqrwav(t,ThrshLim,freq))
grid
ylim(ylim*1.1)

freq = 0.25;
ThrshLim = -0.5;

figure
plot(t, sqrwav(t,ThrshLim,freq))
grid
ylim(ylim*1.1)

If you want regular repeating pulses with at 50% duty cycle, use TL=0.

Experiment to get the result you want.

[Saurabh Kumar]

My main doubt is, look at the difference between subplot(2,1,1) and subplot(2,1,2). I have just changed the limits on the X-axis but i am getting a different plot.In subplot(2,1,2), Concentrate on x=-10,-15,10,15, the pulses are missing from there when compared to the other figure. Why is it happening, i am just plotting x(t) in both cases, the ony difference is change in limits, why is it generating different plots.