What principle does moving radar use to measure the patrol vehicle's speed?

Moving radar utilizes the Doppler principle to measure the speed of a patrol vehicle. This principle is based on the change in frequency or wavelength of a wave in relation to an observer moving relative to the wave source. When the radar system emits a radio wave towards a moving vehicle, that wave reflects off the vehicle and returns to the radar unit. If the vehicle is moving towards the radar, the frequency of the reflected wave increases, whereas if the vehicle is moving away, the frequency decreases.

By calculating the difference in frequency between the emitted wave and the returned wave, the radar device can accurately determine the speed of the vehicle. This is a key feature of the Doppler effect, which applies not only to sound waves but also to electromagnetic waves, making it essential in speed detection technologies. Other principles mentioned do not directly relate to how radar measures speed, as they focus on different aspects like distance and timing.