Ultra-Wideband Low-RCS Circularly-Polarized Metasurface-Based Array Antenna Using Tightly-Coupled Anisotropic Element

A novel broadband circular-polarized array antenna with ultra-wideband low radar cross section (RCS) is proposed. The array is made up of 2 × 2 identically circular-polarized sub-arrays in a chessboard configuration. Furthermore, each sub-array consists of 2 × 2 tightly coupled metasurfacebased elements with linear polarization. For radiation, each element is excited and fed with 90° phase shift between adjacent ones to perform broadband circular-polarized operation. For scattering, destructive phase difference is created in an ultra-wide band for orthogonally polarized incidence due to the anisotropic structure. Thus, a considerable ultra-wideband RCS reduction involving in-band and out-of-band is achieved based on energy cancellation. By this means, broadband circular-polarized radiation and ultra-wideband low RCS performance can be achieved in a synthesized design process. The prototype is fabricated and measured. A good agreement between measured and simulated results verifies the validity of our design method.