What type of radar does a Radio Altimeter use?

A Radio Altimeter utilizes continuous wave radar technology to measure the altitude of an aircraft above the terrain directly below it. This method operates by emitting a constant frequency signal and analyzing the phase difference between the transmitted and received signals, allowing for precise real-time altitude readings. Continuous wave radar is particularly effective for short-range measurements, making it ideal for the low altitudes an aircraft operates at during approach and landing phases.

Pulsed radar, while used in various applications, typically sends out pulses of energy and waits for the echo, which is not the method employed by a radio altimeter. Doppler radar is used primarily for measuring the velocity of targets, which is not the primary function of a radio altimeter. Laser radar, or LIDAR, uses laser beams for distance measurement but is not applicable in the context of radio altimeters, which rely on radio frequency signals. Therefore, the continuous wave radar is the correct type associated with radio altimeters, given its capability for accurate and instantaneous altitude determination.