Effect of Loading on the RCS of Coplanar Antenna Structures

This paper explores the effect of load terminations on the scattering from antenna structures with sizable metallic surfaces. The concept of antenna scattering decomposition into structural and reradiated scattered fields is used to ascertain the behavior of the radar cross section (RCS) of a metallic coplanar antenna structure with variable loadings. Then, a general analytical load condition that minimizes the bistastic radar cross section of the coplanar antenna structure is derived. The derived formula is used to obtain the regions of feasible passive loads for zero/minimum backscattering for the ultra-wide band (UWB) coplanar antenna. The backscattering minimization levels of this antenna is examined to validate the analytical formula. The results demonstrate the validity of the procedure with almost zero backscattering for the antenna with evident RCS reduction factors. Comparisons between the minimum RCS antenna with antennas of different loadings and with equivalent area metallic plates are presented.