Why does this model not produce a frequency spectrum of the time based pulse signal ?

Having great difficulty using the spectrum analyzer.

Have looked at all of the online help but still cannot master it.

It seems to be asking for a sampling time to be setup ? Which I would expect and understand, but there doesn't appear to be anywhere to do this on the configuration menus for the analyzer.

Answer 1

[Star Strider]

I don’t have the DSP System Toolbox, so I can’t experiment with the Spectrum Analyzer. However, in the documentation under Spectrum Settings is:

• Sample rate (Hz) — The sample rate, in hertz, of the input signals.
• Note: The Spectrum Analyzer block always sets this parameter to Inherited. The sample rate is always the same as the input signal, and cannot be modified directly.

Answer 2

[Derek Eccles]

Thank you Star Strider for taking the time to answer my question.

When I try to run the simulation the reply I get is something along the lines that either the input signal is either continuous or an infinite sample time has been set ?

Does this mean that in order for the spectrum analyser to process a continous analog signal that the user must find a way to sample the continuous analog signal at a suitable sampling rate and then present the samples to the spectrum anayser for analysis ?

If this is in fact the case it appears to be very strange as the spectrum analyser will produce repeated spectra of the original continuous analog signal at the sampling frequency which is of course not the spectrum of the continuous analog signal ?

I have a home user license so MATLAB will not provide any technical support or backup.

If anyone could recommend a good book ?

Thanks, Derek

[Star Strider]

Unfortunately, I don’t have it to experiment with.

From my experience, you will have to sample your analog signal somehow in order for any discrete signal processing functions to work with it. I would concentrate on doing that first, since according to the documentation, functions that you use to process the signal inherit the sampling rate from the signal.

Meanwhile, hope that someone with experience with the DSP Toolbox sees this and provides a definitive solution. (I added a tag and product association, so maybe that will help.)

[Derek Eccles]

Thanks again Star Strider for your input.

I just find it hard to believe the spectrum analyser cannot deal with continuous analog signals. If someone would clarify this point and perhaps recommend a good book I would be most grateful.