Arduino, ModulesHB100 Microwave Doppler Radar Wireless Motion Sensor Module
HB100 Miniature Microwave Motion Sensor is an X-Band Bi-Static Doppler transceiver module. It has a built-in Dielectric Resonator Oscillator (DRO) and a pair of Microstrip patch antenna array,making it ideal for usage in motion detection equipment.
This module is ideal for alarms, motion detectors, lighting control, vehicle speed measurement, and automatic doors.
Doppler Principle
Doppler theory based on time. when radio waves encounter an object in the moving process will be reflected when the waves. the frequency of the reflected wave will hit the object with the movement to change state. If the radio waves encounter an object position is fixed. then the reflected wave frequency and transmitting frequency waves should be equal. If the object moves toward the launch. then the reflected waves will be compressed. that will increase the frequency of the reflected wave; otherwise, the reflected waves frequency decreases.