A Super Diffuse Broadband RCS Reduction Surface Design Based on Rotated Phase Coding Polarization Conversion Metasurfaces

A super diffuse broadband radar cross section (RCS) reduction surface design method based on rotated phase coding polarization conversion metasurfaces (PCMs) is proposed. Multiple PCMs with coding phases are employed for wideband RCS reduction, and the spatial locations of the PCMs are utilized for bistatic RCS reduction since it arouses a spatial phase. Furthermore, it is derived that the Pancharatnam–Berry (P-B) phase provides extra design freedom for bistatic RCS reduction. These three types of phases are combined for optimal wideband bistatic RCS reduction. To facilitate bistatic RCS reduction design, the variance of the scattered field (
$\bar \delta _{E}$
) is derived as an indicator for the evenness of the whole space electric field distribution, and an optimal design method is developed thereafter. For comparison, two RCS reduction surfaces, termed MS1 and MS2, respectively, composed of phase coding PCMs are designed, fabricated, and measured to demonstrate the effectiveness of the proposed method. The MS1 is designed by only using the spatial phase, and multiple coding phases, while MS2 is designed by further exploiting the P-B phase. The MS2 achieves 10-dB monostatic RCS reduction ranging from 8.8 to 25.4 GHz (97.1% relative bandwidth, which is 2.2% better than that of the MS1). More importantly, the MS2 realizes super diffuse characteristics under different incidences. It achieves 10-dB bistatic RCS reduction ranging from 9 to 25 GHz (94.2% relative bandwidth), and the maximum bistatic RCS reduction can reach up to 20 dB. The proposed broadband super diffuse RCS reduction design method is particularly desirable for both monostatic and bistatic RCS reduction of various complex coupling structures.