Trigonometric approximations for the computation of Radar cross sections

Trigonometric approximation methods for the interpolation of the far field of a scatterer lit up by plane waves are presented. The Wacker method, commonly used to determine the far field of an antenna from spherical near field measurements, is adapted to decompose the scattered field in a finite series of vector spherical harmonics. The decomposition coefficients are used to assess the accuracy of the computed field and to efficiently store the far field profile. These coefficients are approximated by trigonometric functions up to a given order which can be estimated from the geometry of the scatterer. In this way an efficient procedure for the interpolation of monostatic and bistatic radar cross sections is obtained.