generate a sine wave that ends at 0

Hello everyone,

As the title says, i'm trying to generate a sine wave that ends at 0. I have this problem when i try to generate a signal with a frquency higher than 1, the signal does not stop at 0.

I use the following code for the sine wave:-

%---------------------

Fs=5000;

f=159.2;

t1=1;

t = 0 : 1/Fs : t1-1/Fs;

A=0.1;

sine=A*sin(2*pi*f*t);

%---------------------

is there any way to make the signal stops at 0? even if that means that the signal moves past the 5000 points.

Regards

Ali

[Steven Lord]

One suggestion: the sinpi function may be of interest to you.

[Sam Chak]

Wow, I don't know the existence of this function (Introduced in R2018b).

https://www.mathworks.com/help/matlab/ref/double.sinpi.html

Thank you @Steven Lord.

Answer 1

[Sam Chak]

Hi @Ali Albaidhani

Are you trying to make the Sine wave to hit 0 at the end of the simulation?

f = 159.2;      % frequency
Fs = 35*f;
desired_Tend = 1;
n = round(f*desired_Tend);
T = 1/f;        % period
t = 0:1/Fs:n*T;
A = 0.1;        % amplitude
x = A*sin(2*pi*f*t);

plot(t, x, 'linewidth', 1.5)
axis([0.99 1 min(x) max(x)])
grid on
xlabel('t')
ylabel('x(t)')
title('Sine Wave')

x(length(t))

[Ali Albaidhani]

Yes, but it also has to start from 0. This is important because i want to be able to repeat the signal.

Also, how did you calculate the new value for Fs to make it reach 0?

[Sam Chak]

Hi @Ali Albaidhani

Fs has to be a multiple of the frequency, f. Similarly, for the sine wave to reach zero at every period , then the end time of the simulation must be a multiple of the period . The closest integer of n before reaching 1 second is . I have edited the Answer.

The plot actually starts from . But the final display was zoomed in and boxed in the axis() command.

Simple, you just have to disable the line by inserting the percent symbol '%' as shown below:

% axis([0.99 1 min(x) max(x)])

[Image Analyst]

What starting and ending t value do you want? When you say "ends at 0" it's not clear whether you're talking about t or y. You might want to use linspace().

[Ali Albaidhani]

I'm talking about y. i don't like using linespace tbh, i find it a lil bit confusing.

[Ali Albaidhani]

thank you sam for your answer.

I just have a problem with n.

How do i calculate it and what if i want a signal that is longer than 1 sec?

[Sam Chak]

Hi @Ali Albaidhani

I have edited the script in the Answer. This allows you to compute the nearest integer.

desired_Tend = 2;
n = round(f*desired_Tend);  % calculate the nearest integer