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.

This is known as Amplitude Modulation (AM). Figure 3-2. An amplitude modulated signal. The demodulation process for AM where the ... and is normally quoted in kilohertz. As an example, the signal may ...

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 ...