Need to make a square pulse w/o a special function

3 次查看（过去 30 天）
Saurabh Sakpal
Saurabh Sakpal 2015-8-3
评论： Star Strider 2015-8-4
hi everyone,
really stuck here, need to make a periodic square (step pulse) that turns on to a certain value at a time, and turns off again. I need to make a code for it as i cant use a prebuilt function like square etc. Preferably use for loops and if statements etc.
can someone help me

请先登录，再回答此问题。

采纳的回答

Star Strider
Star Strider 2015-8-3
No loops needed. Just use the repmat funciton.
See if this does what you want:
LP = 10; % Pulse Length
IP = 10; % Inter-Pulse Interval
NC = 3; % Number Of Cycles
PT = repmat([ones(1,LP) zeros(1,IP)], 1, NC); % Complete Pulse Train
TV = 0:length(PT)-1; % Time Vector
figure(1)
plot(TV, PT, 'LineWidth',1.5)
hold on
plot(xlim, [0 0], '-k')
hold off
axis([0 length(TV) -1.25 1.25])
set(gca, 'YTick', [-1 0 1], 'YTickLabel',{'-a', '', 'a'})
ylabel('Volts')
Experiment to get the result you need. The ‘PT’ assignment is the actual pulse train. You can use it in any subsequent code, such as fft or others. I plotted it here because that seems to be what you want.
  2 个评论
Image Analyst
Image Analyst 2015-8-3
repmat() might be banned by the instructor also.
http://www.mathworks.com/matlabcentral/answers/38787-what-can-be-programmed-without-any-built-in-functions
And a "for" loop is so trivial that I don't even think we need to give an example for a for loop. Same for "if" statements. If he can't even do a for loop or if block, then this link might be helpful: http://www.mathworks.com/matlabcentral/answers/8026-best-way-s-to-master-matlab
Star Strider
Star Strider 2015-8-3
Possibly. We may not know everything we need to about this problem.
If repmat is not allowed, the repmat call could easily be replaced by a single for loop with a serial horizontal concatenation at every iteration.

请先登录，再进行评论。

更多回答（3 个）

Geoff Hayes
Geoff Hayes 2015-8-3
Saurabh - why not use the sine and sign functions to do this? You could try something like
% create an array of 10000 elements linearly spaced from 0 to 10
% (can consider this a time vector of then seconds)
t = linspace(0,10,10000);
% set the amplitude
a = 2.0;
% create the square pulse
y = (a/2)*sign(sin(2*pi*t)) + (a/2);
plot(t,y);
As the result of
sign(sin(2*pi*t))
is an array of values between -1 and +1, then in order to get the range as shown in your figure (which is the interval [0 a]) we just multiply the result by a/2 and then add a/2. Try the above and see what happens!
  1 个评论
Saurabh Sakpal
Saurabh Sakpal 2015-8-4
I want it to be "Aperiodic" and unsymettrical as well. Like o for 20 seconds, off for 80 seconds.
Is there any function that does this?

请先登录，再进行评论。

Saurabh Sakpal
Saurabh Sakpal 2015-8-4
Sorry i want to apologise, i AM allowed to use function. I just wanted to avoid them as it is easier to modify parts of the code rather than a pre built fucntion. But feel free to use functions.
Saurabh Sakpal
Saurabh Sakpal 2015-8-4
Hey guys its not working, as i the repmat function doesnt go as a function of time. I need to pass the pulse as a function of time. Still Stuck.
  1 个评论
Star Strider
Star Strider 2015-8-4
What does ‘its not working’ mean? We cannot guess what you want. You must tell us as specifically as you can.
My repmat code produces a single string of 1s and 0s of whatever length and ratio you want for as many periods as you want. You can specify them individually.
To define it as a function of time, define a time vector for it. The linspace function is perfect for this.

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Matrix Indexing 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by