Radar is a system that uses radio waves to determine and map the location, direction, and/or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations and terrain. A transmitter emits radio waves, which are reflected by the target and detected by a receiver, typically in the same location as the transmitter. Although the radio signal returned is usually very weak, radio signals can easily be amplified, so radar can detect objects at ranges where other emissions, such as sound or visible light , would be too weak to detect. Radar is used in many contexts, including meteorological detection of precipitation air traffic control, police detection of speeding traffic , and by the military.
'P' for 'previous', applied retrospectively to early radar systems
VHF
50-330 MHz
0.9-6 m
Very long range, ground penetrating; 'very high frequency'
UHF
300-1000 MHz
0.3-1 m
Very long range (e.g.ballistic missile early warning), ground penetrating, foliage penetrating; 'ultra high frequency'
L
1-2 GHz
15-30 cm
Long range air traffic control and surveillance ; 'L' for 'long'
S
2-4 GHz
7.5-15 cm
Terminal air traffic control, long range weather, marine radar; 'S' for 'short'
C
4-8 GHz
3.75-7.5 cm
Satellite transponders; a compromise (hence 'C') between X and S bands; weather
X
8-12 GHz
2.5-3.75 cm
Missile guidance,marine radar, weather, medium-resolution mapping and ground surveillance; in the USA the narrow range 10.525 GHz ±25 MHz is used for airport radar. Named X band because the frequency was a secret during WW2.
Ku
12-18 GHz
1.67-2.5 cm
High-resolution mapping, satellite altimetry; frequency just under K band (hence 'u')
K
18-27 GHz
1.11-1.67 cm
From German kurz, meaning 'short'; limited use due to absorption by water vapour, so Ku and Ka were used instead for surveillance. K-band is used for detecting clouds by meteorologists, and by police for detecting speeding motorists. K-band radar guns operate at 24.150 ± 0.100 GHz.
Ka
27-40 GHz
0.75-1.11 cm
Mapping, short range, airport surveillance; frequency just above K band (hence 'a') Photo radar, used to trigger cameras which take pictures of license plates of cars running red lights, operates at 34.300 ± 0.100 GHz.
mm
40-300 GHz
7.5 mm - 1 mm
Millimetre band , subdivided as below. The letter designators appear to be random, and the frequency ranges dependent on waveguide size. Multiple letters are assigned to these bands by different groups. These are from Baytron, a now defunct company that made test equipment.
Q
40-60 GHz
7.5 mm - 5 mm
Used for Military communication.
V
50-75 GHz
6.0 - 4 mm
Very strongly absorbed by the atmosphere.
E
60-90 GHz
6.0 - 3.33 mm
W
75-110 GHz
2.7 - 4.0 mm
Used as a visual sensor for experimental autonomous vehicles, high-resolution meteorological observation, and imaging.
