A Flexible Low Profile and RCS Broadband Dual Circularly Polarized Metasurface Antenna

This paper presents a low-profile broadband dual circularly polarized antenna with flexible configuration of peripheral metasurface to implement diversified functions, for example, reduction of radar cross section (RCS). The core metasurface antenna based on the theory of characteristic mode consists of $3\times 3$ modified subwavelength square metal patches as well as an inductive microstrip side feed structure with an overall low profile of 0.06 $\lambda_{0}$ at 9.6 GHz and the peripheral metasurface is a topologically optimized random array of I-shaped unit cells. Simulation results show that the bandwidth of 28.9%, the normal circular polarization axial ratio bandwidth of 19.5%, and the normal gain greater than 7.84 dBi. Meanwhile, more than 9.2 dB RCS reduction is achieved with a slightly negative influence on radiation characteristics at 8.45 GHz.