What method do radar systems use to distinguish between moving and stationary objects?

Radar systems utilize the Doppler effect to differentiate between moving and stationary objects. When a radar signal is transmitted and reflects off an object, the frequency of the returned signal may change if the object is in motion relative to the radar system. This change in frequency is known as the Doppler shift.

For stationary objects, there is no relative motion between the radar and the object, so the frequency of the returned signal remains constant. In contrast, moving objects will cause a shift in frequency; if the object is moving towards the radar, the frequency will increase, and if it is moving away, the frequency will decrease. By analyzing these frequency changes, the radar system can effectively identify and distinguish moving objects from stationary ones.

This method is crucial because it allows for precise tracking and monitoring of objects, enhancing the radar's functionality in various applications such as traffic enforcement, aviation, and maritime navigation. Other methods mentioned, such as analyzing time delays or using visual identification systems, do not specifically address the mechanism for distinguishing between stationary and moving objects as accurately as evaluating Doppler shifts does.