Abstract :
Many detectors of the instantaneous frequency, f1, of an FM signal exist. All of these systems (slope detector, limiter-discriminator, phase-locked loop, etc.) either process the signal after all amplitude variation has been removed or ignore any variations in amplitude. In addition, most detectors have no selectivity due to baseband signal processing. The only detector that provides some selectivity through signal processing at baseband is the phase-locked loop, PLL. However, the amount of selectivity obtainable is severely limited by stability criteria of the feedback loop.
