TABLES OF RADAR CROSS §ECTI0N5 OF HEMISPHERES ON PERFECTLY CONDUCTING GROUND PLANES

摘要

it is proposed that a hemisphere be used as the standard target when radar cross section measurements must be made of a target on or near a ground plane. These tables enable the radar cross section of any hemisphere whose radius is in the range 0.1 to 10.0 wavelengths to be determined for angles of observation up to 30 from the horizontal. Asymptotic expressions are presented for hemispheres outside the size range of the tables. A sphere is commonly used as the standard target in the calibration of radar cross section measurements because its backscatter cross section is invariant with aspect angle and is readily calculable to any desired order of accuracy. If however, the target undergoing measurement is located on or near a ground plane, complications arise if a sphere is to be used as the standard target because of the additional ray paths introduced between the radar and the sphere by reflections from the ground plane, and because the sphere can couple to itself, thus modifying its scattering characteristics, by other reflections from the ground plane. In general therefore the radar cross section of a sphere above a ground plane is not readily predictable, and will be strongly dependent upon the height of the sphere above the ground plane and the aspect angle. Thus the generally desirable properties of the sphere in isolation are no longer evident.