Multiplying sine wave with step function

Hi again!

I'm trying to produce a sampled data vector of a sine wave with the following parameters:

• Amplitude 0.187
• Signal Freq. 187Hz
• Sampling rate 1600s^-1

I am running into an error and cannot figure out what the issue is with element wise multiplication of the step function and the sine wave. Code is as follows:

nn = -3:14; % index vector
uu = double(nn >= 0);% unit step
Ts = 1.6e-3;% sample time
Fs = 1600; % sample rate
t = linspace(-3, 14, Fs); % time
w = 2*pi*187; % omega
xx = 0.187*sin(w*t);% x(t) = 0.187sin(w*t)
xxuu = xx .* uu; % multiplying step function with sine wave
stem(t, xxuu)% stem plot

I am not entirely sure if this is the best way to go about this problem either. My code includes some hints I got from this site.

Answer 1

[Ameer Hamza]

I am not sure how you defined 'uu' vector. But the following code works fine

Ts = 1.6e-3;% sample time
Fs = 1600; % sample rate
t = linspace(-3, 14, Fs); % time
uu = 1*(t>=0);
w = 2*pi*187; % omega
xx = 0.187*sin(w*t);% x(t) = 0.187sin(w*t)
xxuu = xx .* uu; % multiplying step function with sine wave
stem(t, xxuu)% stem plot

[xRah]

I tried to generate a unit step function with 1 sample time advance using the index-vector nn, which is how the 'uu' came about.

[xRah]

oh and the index vector is supposed to be -3:14

[xRah]

i seem to have forgotten it -.-

Answer 2

[madhan ravi]

 uu = @(nn) +(nn >= 0);
 xxuu = xx .* uu(t)

Answer 3

[Paul]

Change one line to:

xxuu = xx .* (t >= tstep);  % set tstep as the time when the unit step is applied

Answer 4

[xRah]

Thank you all for your input and help :)