Radars

Radar, short for radio detection and ranging, is a system that uses radio waves to locate and characterize objects. It transmits short pulses of radio energy and listens for echoes. By measuring the time delay between transmission and reception, radar determines range; the direction of the antenna provides azimuth and sometimes elevation. Doppler shifts in the returned signal reveal radial velocity. Scanning the antenna allows mapping of areas and tracking of multiple targets.

A typical radar comprises a transmitter, antenna, receiver, a duplexer to separate transmit and receive paths, and a signal processor that extracts range, angle, velocity, and sometimes height. Modern radars often use solid-state transmitters and phased-array or other electronically steered antennas, enabling rapid electronic beam scanning without moving parts.

Radars are deployed in many domains. Weather radar detects precipitation and its motion, providing estimates of rainfall rates and storm dynamics. Air traffic control radars monitor aircraft positions and speeds for coordination and safety, sometimes using secondary surveillance radars that read transponder signals. Marine radars aid navigation and collision avoidance. Military radars provide surveillance, target identification, and fire control, with specialized forms such as airborne, ground-based, and shipborne systems. Specialized techniques include synthetic aperture radar for high-resolution imaging and ground-penetrating radar for subsurface detection.

History notes that rudimentary radar emerged in the early 20th century, with significant development in the 1930s and 1940s driving modern systems. Today, radar remains essential across civilian safety, meteorology, aviation, and defense. Limitations include dependence on object reflectivity, atmospheric conditions, ground clutter, and resolution constraints set by wavelength and antenna size.