When driving on highways, we see the sign "Speed monitored by Radar". Based on radio wave progopation research by various scientists as early as 1890s, the Radar device was invented at the US Naval research laboratory in 1940s, to detect aircrafts, ships, distance between objects and velocity at which the objects travel. The term radar was designated by U.S. Navy Lieutenant Commander Samuel M. Tucker and F. R. Furth.

Radar has been used in other applications such as weather forecasting (Doppler Radar), missile systems, autonomous vehiles and object detection (blind spot monitoring in vehicles), to name a few.

Radar Technology

The Radar devices operate in radio wave range, with wavelength varying from 1 cm to 104 km. The velocity, wavelength and frequency are related by

c = f x λ

c is velocity of light = 3 x 108 m/s

f - frequency

λ - wavelength (m)

Radar devices operating at wavelength of 10 cm or 0.1 m will be operating at frequency of

f = c / λ = 3 x 108/0.1 = 3 x 109 = 3 GHz

The police radar guns operate in one of the bands X, Ku, K or Ka frequencies [3]. The radar devices send a series of radio waves (electromagnetic pulses) at a certain frequency (f). These waves intercept a moving target, which reflects back the radio waves, commonly known as the echo. The difference between transmitted frequency and echo frequency is Δf. The radar devices operate using the doppler effect.

The velocity (v) is computed using the equation shown below.

v = (Δf / f) x c/2

Reference

[1] Radar Techonology

[2] Frequency and Electromagnetic Spectrum

[3] Microwave and Radar Frequencies

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