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For example, consider a radar with a beam width of one degree and an antenna that rotates once every ten seconds, or 36 degrees per second. An object will be painted by the beam for only 1/36 of a second as the one-degree beam sweeps over it. If the radar has a PRF of 500, the object will be painted with 14 pulses per scan at most.
Radar cross-section (RCS), denoted σ, also called radar signature, is a measure of how detectable an object is by radar. A larger RCS indicates that an object is more easily detected. [1] An object reflects a limited amount of radar energy back to the source. The factors that influence this include: [1] the material with which the target is made;
The radar beam has a width of about 10 degrees, and sends a pulse every 2.5 degrees of rotation, so a target will not produce a single blip, but a number of them. For targets located far from the centreline, the radar would produce 4 or 5 individual blips as the scanner rotated, causing a short arc about 10 degrees wide to show on the display.
Given an example antenna that generates a beam of 2 degrees width – fairly typical – a conical scanning radar might move the beam 1.5 degrees to one side of the centerline by offsetting the feed slightly. The resulting pattern, at any one instant in time, covers the midline of the antenna for about 0.5 degrees, and 1.5 degrees to the side.
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.
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).
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.