Repeating a Waveform in MATLAB

I need to create a sine wave with a certain firing angle in the positive and negative cycles (both firing angles differ), and also different clipping values in the positive and negative cycles.

I did it for one cycle basically, using the following code:

clear

clc

com0 = 'Insert the frequency of the sine waveform - ';

f = input(com0);

com1 = 'Insert the time at which the positive cycle starts - ';

t1 = input(com1);

com2 = 'Insert the time at which the negative cycle starts - ';

t2 = input(com2);

com3 = 'Insert the clipping value desired during positive cycle - ';

c1 = input(com3);

com4 = 'Insert the clipping value desired during negative cycle - ';

c2 = input(com4);

T = 1/f; %Period of the Signal

t3 = (asin(c1))/(2*pi*f);

t4 = (asin(c2))/(2*pi*f);

if t3 < T/4

tx = ((T/2)-t3):0.00001:(T/2);

x = sin(2*pi*f*tx);

end

if t3 >= T/4

tx = t3:0.00001:(T/2);

x = sin(2*pi*f*tx);

end

ty = t2:0.00001:T;

if t4 < (3*T)/4

ty = (t4+T):0.00001:T;

y = sin(2*pi*f*ty);

end

if t4 >= (3*T)/4

ty = t4:0.00001:T;

y = sin(2*pi*f*ty);

end

line(xlim(), [0,0], 'LineWidth', 1, 'Color', 'k');

hold on

plot(tx,x)

plot(ty,y)

grid

plot([t1 t1],[0 c1])

if t3 < T/4

plot([t1 ((T/2)-t3)],[c1 c1])

end

if t3 >= T/4

plot([t1 t3],[c1 c1])

end

plot([t2 t2],[0 c2])

if t4 < (3*T)/4

plot([t2 (t4+T)],[c2 c2])

end

if t4 >= (3*T)/4

plot([t2 t4],[c2 c2])

end

xlim([0 T])

hold off

How can I repeat the same waveform for at least two more periods (or cycles)?

Answer 1

[Soumya]

Hi Hasan,

To repeat the waveform that you have designed for any desired number of periods (or cycles), you will need to make a few modifications to your code:

1.Define a variable to specify the number of cycles you want to plot:

 com5 = 'Insert the number of cycles to plot - ';
 numCycles = input(com5);

2. Create a “for” loop which iterates over the number of cycles you have defined. A time shift “shift = k * T” has to be created to ensure that each cycle starts at the correct time position on the plot:

for k = 0:(numCycles - 1)  

shift = k * T;

3. Within the loop, we can shift the sine wave segments for each iteration. The “line” function draws a horizontal line from “x = shift” to “x = shift + T at y = 0”, with a specified line width and color:

line([shift shift+T], [0, 0], 'LineWidth', 1, 'Color', 'k'); 
plot(tx + shift, x, 'b')
plot(ty + shift, y, 'b')

4.The conditional statements that you used to determine the endpoints of the clipped waveform segments should also be shifted:

plot([t1 t1] + shift, [0 c1], 'r')
if t3 < T/4
    plot([t1 ((T/2)-t3)] + shift, [c1 c1], 'r')
else
    plot([t1 t3] + shift, [c1 c1], 'r')
end
plot([t2 t2] + shift, [0 c2], 'r')
if t4 < (3*T)/4
    plot([t2 (t4+T)] + shift, [c2 c2], 'r')
else
    plot([t2 t4] + shift, [c2 c2], 'r')
end

5.Set the x-axis limits to “xlim([0 numCycles*T])” to cover the entire duration of all plotted cycles.

This is the plot generated by applying the changes to the code, displaying the waveform over three periods (or cycles):

I hope this helps!