The author discusses how cheap RCWL-0516 microwave motion sensors work, revealing the technical details behind their functioning. The chip inside acts as an infrared motion sensor, picking up millivolt-level changes caused by moving objects. Surprisingly, the sensor functions as both a receiver and transmitter, depending on modifications made. It can be used in a bistatic radar setup, where another module acts as the receiver. The sensor can also be utilized as a speed sensor by analyzing the IF signal. The performance indoors is good, but outdoors it is inconsistent due to lack of static returns. Overall, the sensor’s functionality is unique and versatile.
https://10maurycy10.github.io/projects/motion_sensor_hacking/