MATLAB: Simulink: Sine wave generation. Configuration problem.

Question

Hi, While using Simulink, I simply connect a 'sine wave generator' (picked from Simulink>>Sources) to the scope and set the frequency at 100*pi rad/s.

However, on running the simulation, I get a randomly increasing waveform and not a sinusoidal signal of above freq. However, if I set a frequcny such as 1 rad/s, a perfect sine wave is obtained.

I think I must choose a 'continuous' scale to run it and right now maybe a 'discrete scale' is chosen with large step size. May someone suggest a possible remedy?

Thanks.

Answer 1

By default, the Simulink solver chooses the time steps using:

dt = (t_stop-t_start)/50

With the default parameters, it gives 50 Hz, or a period of 0.02. this is why you do not see the 100rad/s sine way proprerly... Nyquist criteria and aliasing!

I made the following blog post exactly on this topic:

http://blogs.mathworks.com/seth/2009/07/14/refining-the-output-of-a-simulation/