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Dwell time (T D) in surveillance radar is the time that an antenna beam spends on a target. [1] The dwell time of a 2D–search radar depends predominantly on the antenna's horizontal beam width θ AZ, and; the turn speed n of the antenna (in rotations per minute or rpm, i.e. 360 degrees in 60 seconds = multiplied by a factor of 6).
With this calculation, the horizon for a radar at a 1-mile (1.6 km) altitude is 89-mile (143 km). The radar horizon with an antenna height of 75 feet (23 m) over the ocean is 10-mile (16 km). However, since the pressure and water vapor content of the atmosphere varies with height, the path used by the radar beam is refracted by the change in ...
Five definitions of the beam width are in common use: D4σ, 10/90 or 20/80 knife-edge, 1/e 2, FWHM, and D86. The beam width can be measured in units of length at a particular plane perpendicular to the beam axis, but it can also refer to the angular width, which is the angle subtended by the beam at the source.
The resolution of any radar depends on the width of the beam and the range to the target. For example; a radar with 1 degree beam width and a target at 120 km (75 mi) range will show the target as 2 km (1.2 mi) wide. To produce a 1-degree beam at the most common frequencies, an antenna 1.5 kilometres (0.93 miles) wide is required.
Radar engineering is the design of technical aspects pertaining to the components of a radar and their ability to detect the return energy from moving scatterers — determining an object's position or obstruction in the environment.
The radar mile is the time it takes for a radar pulse to travel one nautical mile, reflect off a target, and return to the radar antenna. Since a nautical mile is defined as 1,852 m, then dividing this distance by the speed of light (299,792,458 m/s), and then multiplying the result by 2 yields a result of 12.36 μs in duration.
The antenna panels used with phased array radar may be designed with an overlap that fills in any gap above a fully operational radar. Fan beam antenna pattern. The radiation pattern of a rotating truncated parabolic antenna for radar fixed pedestal has a fan shaped beam with a vertical gap in coverage. Objects located directly above the radar ...
A fire-control radar (FCR) is a radar that is designed specifically to provide information (mainly target azimuth, elevation, range and range rate) to a fire-control system in order to direct weapons such that they hit a target. They are sometimes known as narrow beam radars, [1] targeting radars, tracking radars, or in the UK, gun-laying radars.