Dynamic Signal Acquisition

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How do you analyze a carrier frequency.

I usign the "Formula Waveform.vi" shipped with Labview 6i. The formula is a*cos(2*3.14*30000*t)*cos(2*3.14*1000*t). It basically ends up being a 30 khz waveform in a 1 khz envelope. When I use the Power Spectum.vi I only "see" the 30 Khz waveform. How can I view the 1 KHz envelope.
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The spectrum of an amplitude modulated signal as you describe will be made of two peaks located at frequencies :
(carrier freq + message freq) and (carrier freq - message freq)
So, we should observe a peak at 29 kHz and a peak at 31 kHz when using the formula and values you mention.(Pls see attached VI)
If you are using a sine wave signal as a modulating signal, you may try to use the "Extract single tone.vi" in order to get the frequency of this signal - That's what is described in the attached VI.
You also need to make sure you are using appropriate sampling frequencies (>60kS/s) in order to respect the Nyquist criterion.
I hope this will help.
Gerald
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