Low RCS, Broadband Polarization Conversion Metasurface Antenna Based on Reactance Loading

A reactance-loaded polarization conversion metasurface (PCMS) is presented and exploited to realize a metasurface antenna (MTA) with both low radar cross section (RCS) and broadband radiation. Distinct from the conventional low-RCS PCMS, a metallic surface with etched open and closed slits is integrated into a PCMS consisting of double L-shaped particle pairs. Due to the edge capacitance induced by open slits and the surface inductance imposed by closed slits, the PCMS is endowed with reactance features that act as a perturbation to modulate the near-field interactions, thereby expanding the polarization conversion bandwidth. Besides, the reactance-loaded metallic surface, which has the same period as L-shaped particle pairs, combined with the grounded substrate, constitutes a broadband metasurface radiator. With the help of characteristic mode analysis, a linearly polarized aperture-coupled PCMS antenna is proposed, which effectively stimulates two resonant modes with broadside radiation to help bring about a broad operating bandwidth of 45.52%. Subsequently, the checkerboard-layout PCMS array is coupled to a sequentially feeding network through apertures on the ground plane, implementing a circularly polarized MTA with a broad 3 dB axial ratio bandwidth of 20.11%. Relying on phase cancellation and outstanding polarization conversion behaviors, an ultrawideband RCS reduction bandwidth of 7–39 GHz (139.13%) is also available.