Design of Low-RCS Transmitarray with Integrated Radiation and Scattering Control

This paper presents a low radar cross section (RCS) circularly polarized transmitarray antenna (CPTA) based on multimode metasurface. The proposed element comprises slotted top patch layer (BitR) and bottom patch layer (BitT), separated by a perforated ground and interconnected via a vertical metallic post. By engineering the anisotropy of the BitR layer along the x y and u v axes, the element achieves in-band linear-to-circular transmission and out-of-band cross-polarized reflection. Phase manipulation is achieved by independently rotating both the BitR and BitT layers between their two discrete states. The BitR layer is adopted to simultaneously achieve quasi-2-bit in-band transmission phase compensation and out-of-band reflection gradient phase control. To validate this integrated control scheme, a 16 × 16 CPTA prototype fed by a horn antenna is designed and analyzed. Simulation results demonstrate that the transmission beam of designed CPTA can accurately steer to the preset angle of 30°, with a gain of 21 dBi and the cross-polarization level being approximately -11.8 dB. Besides, the scattering beam can be deflected to on-demand angel, alongside an out-of-band RCS reduction exceeding 6 dB.