Radar cross section reduction using electromagnetic band-gap checkerboard surfaces

Electromagnetic band-gap (EBG) structures have noteworthy electromagnetic characteristics that include their phase variations with frequency. When combining perfect electric conductor (PEC) and EBG structures on the same ground plane, the scattering fields of the ground plane are altered because of the scattering properties of EBG structures. The scattering fields are cancelled along the principal planes because PEC and EBG structures are anti-phase at the resonant frequency. To make the scattered fields symmetrical under plane wave incidence, a square checkerboard surface is designed to form constructive and destructive interference scattering patterns to reduce the intensity of the scattered fields toward the observer; thus reducing the radar cross section (RCS). To increase the 10-dB RCS reduction (compared to a PEC surface) bandwidth, checkerboard surfaces of two different EBG structures on the same ground plane are designed. Thus, significant RCS reduction over a wider frequency bandwidth of about 63% is achieved.

Another design is a hexagonal checkerboard surface that achieves the same RCS reduction bandwidth because it combines the same EBG designs. The hexagonal checkerboard design further reduce the RCS than square checkerboard designs because the reflected energy is re-directed toward six directions and a null remains in the normal direction.

A dual frequency band checkerboard surface with 10-dB RCS reduction bandwidths of 61% and 24% is realized by utilizing two dual-band EBG structures, while the surfaces maintain scattering in four quadrants. The first RCS reduction bandwidth of the dual band is basically the same as in the square checkerboard design; however, the present surface exhibits a second frequency band of 10-dB RCS reduction.

Finally, cylindrically curved checkerboard surfaces are designed and examined for three different radii of curvature. Both narrow and wide band curved checkerboard surfaces are evaluated under normal incidence for both horizontal and vertical polarizations. Simulated bistatic RCS patterns of the cylindrical checkerboard surfaces are presented.

For all designs, bistatic and monostatic RCS of each checkerboard surface design are compared to that of the corresponding PEC surface. The monostatic simulations are also compared with measurements as a function of frequency and polarization. A very good agreement has been attained throughout.