Editorial Feature

What is a Radar Gun?

A radar gun is a device for measuring the speed of moving objects. Invented by Bryce K. Brown in 1954, the radar gun is often used in law-enforcement purposes to calculate the speed of moving vehicles.

The radar gun is a Doppler radar unit that can be static, vehicle-mounted or hand-held. It measures the speed of vehicles by detecting the change in the frequency of reflected radar signal produced by Doppler effect. However, vehicle separation is necessary for proper operation of radar gun while monitoring the speed of the vehicle.

Design of Radar Gun

Radar guns have been used since many years, and the recent ones were found to have improved safety and performance when compared to the early units. Most of the early radar gun units consist of LED displays and transistors, and the displays were driven directly. Some of the radar guns were wired remote-controlled units provided with an auxiliary display interfaced via a black box.

However, the current remote units have become more sophisticated with microprocessors and serial control, which in turn resulted in the development of advanced radar units with RS-232 direct outputs.

Working Principle

The radar gun includes a radio wave transmitter integrated with a radio wave receiver. The gun emits radio waves at a particular frequency so that the radio waves travel via the air and bounce off the moving vehicles. Some of these reflected waves will return back to the radar gun, and the waves that are reflected from the vehicles undergo a Doppler Shift.

This Doppler shift in turn causes a change in the frequency of the radio waves. The radar gun makes use of this frequency change to measure the speed of the vehicle.


Radar guns are primarily used in law enforcement to sense the moving vehicle speed and record traffic violations. With the introduction of video recording systems, the validation of revealed traffic violation has been significantly improved.


Although radar guns have many different uses, it is mostly used as a tool for police men to measure vehicle speed. Following World War II, the radar guns were first introduced by law enforcement department as a speed measurement tool. The radar gun is not only used to monitor the vehicle speed, but also to catch speeders and alert drivers traveling at unsafe speeds on the highways.

Radar guns are also being used for the measurement of sports performance. One product on the market includes the Pocket RadarTM:

Sources and Further Reading

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