# Generate Square Wave

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Onur Öçalan on 16 Dec 2011
Hi everybody;
I want to create a rectangular wave with a specific function. For example,
the wavelength of the wave = 20 milliseconds
the wave width = 1.2 milliseconds
How do I do with Matlab ?
Thanks.
Onur Öçalan on 17 Dec 2011
And I cann't put this value to Nidaq 6008 digital out line ??

Paulo Silva on 16 Dec 2011
Here's my crazy way to do it, I'm assuming some values for example the sampling time. This way doesn't require any toolboxes, another way to do it easily would be to use the Control System Toolbox™ gensig function that I usually use.
l=20e-6;
w=1.2e-6;
Ts=1e-9;
t=0:Ts:l; %generate the time vector
s=0:Ts:w; %generate a piece of the wave, the one with zeros
s0=s*0;
%generate another piece of the wave, the one with ones
s1=s*0+1;
s=[s s1]; %combine them for one period of the wave
s=repmat(s,1,round(l/(2*w)+1)); %create the entire wave from that first piece
%view the wave
plot(t,s((1:size(t,2))))
ylim([-0.5 1.5])
Paulo Silva on 18 Dec 2011
l=20e-6;
w=1.2e-6;
Ts=1e-9;
t1=0:Ts:w;
t0=w+Ts:Ts:l-Ts;
s1=ones(size(t1));
s0=zeros(size(t0));
s=[s1 s0];
N=2; %How many repetitions of the wave
ss=repmat(s,1,N);
t=0:Ts:N*l-Ts;
plot(t,ss)
ylim([-0.5 1.5])

Dr. Seis on 17 Dec 2011
signal_length = 20e-6; % length of signal in seconds
wave_length = 1.2e-6; % wavelength of rectangle pulse in seconds
amplitude = 0.75; % amplitude of wave
dt = 1e-9; % time increment in seconds
time = 0:dt:signal_length; % time samples in seconds
% Define the rectangle signal timeseries
rectsignal = sign(sin(2*pi*time/wave_length)).*ones(size(time))*amplitude;
% Plot the timeseries
plot(time,rectsignal,'r-');
##### 2 CommentsShowHide 1 older comment
Onur Öçalan on 17 Dec 2011
http://imageshack.us/photo/my-images/714/20111217100355.jpg/
I want just like it...
Thanks.

Dr. Seis on 18 Dec 2011
This should work:
dt = 1e-9; % time increment (in seconds)
maxtime = 200e-6; % maximum length of signal (in seconds)
time = 0:dt:maxtime; % time samples (in seconds)
wavelength = 20e-6; % distance between beginning of each pulse
wavewidth = 1.2e-6; % width of each pulse
rectpulse = ones(1,round(wavewidth/dt)); % Define width of rectangle pulse
operator = zeros(size(time)); % Set operator to zeros
operator(mod(time,wavelength)==0) = 1; % Place 1 at each pulse location
rectsignal = conv(operator,rectpulse); % Convolve rectpulse w/ operator
rectsignal = rectsignal(1,1:length(time)); % Remove any extra traces
plot(time,rectsignal); % Plot the signal