How is the scan of a search radar performed?
============ There are several possible scan techniques for search radars. The “classical” old fashioned search radars use a “fan beam” antenna, i.e. narrow on the azimuth plane and tall in the elevation plane, to avoid the need to scan in elevation, rotating over 360°. The limitation of this system is that it does not provide information about target elevation, and the target data are limited to azimuth and range (so called bidimensional, or 2-D radar). The elevation information, when needed, is achieved by external means: commercial aircraft, for instance, transmit the flight level info via their secondary-radar transponder; in air-defence systems, dedicated “higth-finder” radars, with a so called nodding beam (a fan beam rotated by 90°) scanning in elevation only, where used, in association with the main radars, to detect the flight level of the objects to be intercepted. To extract the tridimentional information without rely on external means, capability of scanning the antenna bea
