Conceptually the circuit there is simple, consisting of the ultrasonic receiver, followed by a transistor amplifier for the modulated wave, then a diode for demodulation, another transistor ...

At the most basic level, AM radio works by generating a carrier wave with an oscillator, and then modulating the amplitude ... built a basic circuit around a TA7642 AM amplifier/demodulator ...

In this section, focusing on the specific example of two-level amplitude-modulated data, we explain this machine-learning approach to demodulation and discuss its data-retrieval accuracy.