modified nonabsorptive chessboard configuration for radar cross section reduction

This paper presents a modified nonabsorptive radar cross-section (rcs) reducer based on previous reports. the design is a flat 4×4 chessboard, followed by two upper and lower dielectrics with the same relative permittivity and thickness. the lower dielectric is metal-backed. the incident wave to the surface of the upper dielectric penetrates through the structure. some parts of the incident wave is reflected back by the black (metal) sections of the chessboard in the middle, while the remaining parts of the wave penetrates further in the lower dielectric until it is totally reflected by the ground plane. the relative permittivity and dielectric thicknesses are computed analytically to make a 180° phase difference between the two reflected waves. this results in destructive interference and makes a null in the expected angle of reflection. the theory of operation is deduced generally for any angle of incidence as well as both principal polarizations. first, the designing procedure is done with matlab, then the practical design is simulated with ansys hfss13 and finally, it is fabricated and its monostatic rcs reduction property is measured experimentally. at least 10db rcs reduction compared to a metal plate of the same size is guaranteed from 8.5 to 17.5 ghz for normal incidence.