In my university lectures I have generated an FM signal (for instance with carrier frequency of 2GHz, frequency deviation equal to 100kHz, and modulating frequency equal to 100kHz.)
In order to perform the demodulation, my teacher has followed these steps:
- Choosing a high resolution bandwidth in order to incorporate all the side bands inside one single peak (obviously it is not good if we want to analyze the spectrum properties.)
- Choosing as center frequency a point in the transition between the peak and the "null" part of the spectrum.
- Switching to time domain and visualizing the modulating signal.
I have some questions about step 1 and 2:
- about 1: Why do we have to choose a so large RBW (for instance 3MHz?)
- about 2: Why do we have to choose a point of demodulation which is not the peak of the spectrum?
My professor has said that choosing the peak frequency will lead to a demodulated signal with 0 voltage dynamic. Why?