Wide-Angle Surface Wave Reduction Based on Spatial Kramers–Kronig Media

Electromagnetic (EM) surface waves are typically undesired due to their adverse effects, such as inducing interferences or leakages in EM compatibility and causing backward radiations in patch antennas. Thus, it is imperative to develop an efficient method to suppress these undesired surface waves. Here, we propose a wide-angle surface wave absorber based on spatial Kramers–Kronig (KK) media. The specific spatial permittivity profile ensures that surface waves impinging on the interface are nearly fully absorbed within a wide incident angle range. To demonstrate this concept, we design a thin spatial KK medium absorber comprised of gradient mesoscopic structures, which is integrated into a circularly polarized patch antenna. This integration results in a reduced-surface-wave (RSW) circularly polarized antenna, exhibiting a significantly improved front-to-back ratio (FBR) (by suppressing forward surface waves) and 3-dB axial ratio (AR) beamwidth (by suppressing reflected backward surface waves). Experimental measurements of the fabricated prototype align with simulated results. Our approach is robust and scalable to higher frequencies, offering a simple and nondestructive method in EM compatibility to eliminate surface-wave-induced mutual coupling between multiple devices without compromising their inherent performances.