He’s broken down the modulation and demodulation circuits into their basic op-amp stages with examples of what the signal should look like on a scope after each stage. That’s the beauty here.

Demodulation of frequency modulation (FM) signals can be done in many ways. There are FM discriminators, ratio detectors, quadrature detectors, phase lock loop designs, and even methods of getting ...

The modulation-domain view allows us ... parameters to provide frequency or phase demodulation, respectively. In this example, it shows that the frequency of the demodulated pulse train is hopping ...