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In those situations, it is useful to use a related quantity called the normalized radar cross-section (NRCS), also known as differential scattering coefficient or radar backscatter coefficient, denoted σ 0 or σ 0 ("sigma nought"), which is the average radar cross-section of a set of objects per unit area:
Radar echoes, showing a representation of the carrier. Pulse width also determines the radar's dead zone at close ranges. While the radar transmitter is active, the receiver input is blanked to avoid the amplifiers being swamped (saturated) or, (more likely), damaged.
The radar measures the distance to the reflector by measuring the time of the round trip from emission of a pulse to reception, dividing this by two, and then multiplying by the speed of light. To be accepted, the received pulse has to lie within a period of time called the range gate .
The radar frequency is also chosen in order to optimize the radar cross-section (RCS) of the envisioned target, which is frequency-dependent. Examples of propagation windows are the 3 GHz (S), 10 GHz (X), 24 GHz (K), 35 GHz (Ka), 77 GHz (W), 94 GHz (W) propagation windows.
Optical cross section (OCS) is a value which describes the maximum amount of optical flux reflected back to the source. [1] The standard unit of measurement is m 2 /sr. OCS is dependent on the geometry and the reflectivity at a particular wavelength of an object. Optical cross section is useful in fields such as LIDAR.
When it is exactly zero the radar is a monostatic radar, when it is close to zero the radar is pseudo-monostatic, and when it is close to 180 degrees the radar is a forward scatter radar. Elsewhere, the radar is simply described as a bistatic radar. The bistatic angle is an important factor in determining the radar cross section of the target.
The S-300PMU could engage targets with a radar cross section of at least 0.2 square metres (2.2 sq ft) and a maximum velocity of 1,300 metres per second (4,300 ft/s) at altitudes between 25 metres (82 ft) and 27,000 metres (89,000 ft). [21] It could also engage surface targets at ranges up to 30 kilometres (19 mi). [21] [clarification needed]
It is a horizontal cross-section through radar data. This way, one can compare precipitation on an equal footing at difference distance from the radar and avoid ground echoes. Although data are taken at a certain height above ground, a relation can be inferred between ground stations' reports and the radar data.