Frequency-Multiplexed Spin-Decoupled Metasurface for Low-Profile Dual-Band Dual-Circularly Polarized Transmitarray With Independent Beams

This article presents a theoretical and experimental demonstration of a frequency-multiplexed spin-decoupled metasurface, along with its application to a dual-band dual-circularly polarized (CP) transmitarray (TA). The meta-atom consists of Ku- and K-band receiver-transmitter structures constructed of CP receiving patches and linearly polarized transmitting patches. By separately rotating the bottom and top patches, two independent phase shifts are achieved in each band. This enables decoupling and independent manipulation of the transmitted right-handed CP (RCP) and left-handed CP (LCP) waves. A low-profile shared-aperture TA with four degrees of freedom for beamforming is constructed using planar CP feeds and a single metasurface. The metasurface shows a thin thickness of $0.12 \lambda _{L}$ ( $\lambda _{L}$ is the free-space wavelength at the center frequency of the low band). The measured results indicate that the maximum overall aperture efficiencies for Ku- and K-bands are 46.2% and 26.9%, respectively. The measured joint gain variation < 3 dB and axial ratio < 3 dB relative bandwidths for RCP/LCP beams are superior to 16.4% and 9.3% for Ku- and K-bands, respectively. The proposed method offers an alternative avenue toward versatility and expansion of integrated functions, and the present TA may have a promising perspective for future space and wireless communications.