What is Radar?
Radar is an incredibly powerful tool for performing object detection and location for a variety of applications. Radar, which is an acronym for radio detection and ranging, uses electromagnetic waves (EW) within the radio frequency (RF) spectrum to detect, locate, track, and identify objects of interest on the ground or in the air over long ranges. At the most basic level, the EW signal is transmitted into the environment and the radar “listens” for a return signal, or echo. A return signal is generated when an object is in the path of the original signal, causing a reflected signal that bounces back to the receiver. It is often assumed that the object commonly referred to as a target, must be metal to reflect a radar signal, but it can be constructed of almost any type of material sufficiently different than the air that the radio wave is propagating through (plastic, rubber, glass, metal, wood, etc.). The time between the transmission of the original signal and reception of the return signal, which is known as time of flight, provides a significant amount of information about the detected object, including its location, distance, velocity, and characteristically unique features of motion which can be used to classify a target.
Since radar uses EWs that are pulsed and received rather than light waves or imaging technology, radar systems can accurately detect objects even under adverse weather and lighting conditions. Other common object detection and location technologies such as optical, infrared, and LiDAR-based sensing devices are significantly degraded. And even though radar is commonly confused with RF detection sensors because both devices detect EW signals, the way these two devices operate is quite different. Instead of sending out its own RF signals, RF sensors actively “listen” for RF signals emitted from other devices. Therefore, if an object is not emitting an RF signal, an RF sensor cannot detect that object (more on this in Chapter 3).