Low-RCS Broadband Miniaturized Polarization Conversion Metasurface Array Antenna Based on Capacitive Loading Technology

This paper introduces a capacitive loading method used to design a polarization conversion metasurface(PCMS) array antenna. This method addresses the compatibility challenges of traditional low-RCS antennas concerning broadband circular polarization radiation, broadband scattering suppression, and aperture miniaturization. The core of the capacitive loading technique is the double-layer patch structure of the PCMS. First, the patches are designed with corner-cutting, which simultaneously excites two orthogonally polarized degenerate modes. This improves the circular polarization purity of the array elements and broadens the axial ratio bandwidth of the array antenna. Additionally, the patches feature cross-shaped slots, and the double-layer patches are interconnected by vertical metal pillars. This configuration increases grid capacitance and introduces parallel capacitance, which lowers the resonant frequency of the metasurface (MTS) radiator, thereby achieving miniaturization. It is noteworthy that this method has minimal impact on the reflection characteristics of the PCMS. Consequently, the radiator of the PCMS array antenna adopts a chessboard layout. The 180° phase difference between the PCMS and the grounded substrate is utilized for phase cancellation, resulting in broadband RCS reduction. The array size of the PCMS array antenna using the capacitive loading method is 3×3. The simulated and measured results are consistent, indicating that the antenna aperture size is only 1.33λ ₀  × 1.33λ ₀  × 0.0984λ ₀ , with a working bandwidth of 40.91%. Furthermore, the RCS reduction bandwidth spans the C, X, and Ku bands.