Multimode Metasurface Inspired Integrated Low RCS Circularly Polarized Transmitarray Antenna

In this letter, an integrated low radar cross section (RCS) circularly polarized transmitarray antenna based on a multimode metasurface is proposed, featuring control of both radiation and scattering properties. To mitigate the inherent coupling between multiple resonant modes, structural anisotropy is introduced along both the x- and y-axes as well as the u- and v-axes. The proposed element comprises three layers: the top layer is a diagonally placed centrally slotted strip with modified diagonal corners to introduce anisotropy along the uv- and xy-directions. The middle layer is a perforated ground plane, and the bottom layer is a centrally slotted strip aligned with the x-axis. The top and bottom strips are connected by a vertical metal post. This compact and integrated element design enables efficient out-of-band reflective cross-polarization conversion and in-band linear-to-circular polarization conversion, with independent phase control. To verify the design, two 16 × 16 prototypes are fabricated and measured, demonstrating a 1 bit coding configuration that enables independent manipulation of radiation and scattering, as well as a 2-bit coding configuration for radiation modulation, together with low-RCS performance.