Re: How to draw a spectrum of Pulse Amplitude Modulated signal?


<ivanatora@xxxxxxxxx> wrote in message
news:1178541359.429108.295770@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hello all!

I have a school project to do about PAM (Pulse Amplitude Modulation),
but these stuff aren't explained at all in our school class. I tried
searching google about PAM spectrum, but I almost didn't find
anything. Even in Wikipedia there was almost nothing useful about PAM.
I'm given a triangle signal with period=T,amplitude=A and a pulse
(square) carrier signal at 1MHz.
I can write this signal in a mathematical way, but I don't know how to
find its spectrum.
I have 2 things to do:
1) Write down an algoritm to calculate the spectrum of the modulated
signal.
2) Draw the spectrum of the modulated signal up to 6MHz.

If you help me with 1) I'll be able to do 2)

Thanks!


Well one way to do this is if you can write this signal in a mathematical
way you can generate samples of that signal, that you can later subject to a
frequency transform. If your interested in frequencies up to 6 MHz then
Nyquist says you need a sample rate of at least 12MHz (I personally would go
beyond just Nyquist). Then generate an array of samples with respect to
time. i.e. t=0 t=8.3E-8 t=1.66E-7 t=2.5E-7 are the first four samples at
Nyquist. Then you can do a DFT or FFT on the samples to get the spectrum.
Whatever the required frequency resolution will determine how many samples
are generated.

Thomas Magma


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