Low-Profile K/Ka-Band Shared-Aperture Phased Array With High Isolation for LEO Satellite Communication

This communication presents a low-profile dual-circularly-polarized shared-aperture phased array with high isolation for K/Ka-band LEO satellite communication. To mitigate mutual coupling between shared-aperture antennas while preventing efficiency degradation, a distributed decoupling method is proposed, where frequency-selective filtering components are introduced into the antenna radiators, coupling structures, and feeding networks. These components are jointly designed to achieve high cross-band isolation with low in-band insertion loss. For K-band decoupling, the high-band (HB) antenna is loaded with shielding vias that form a back cavity and HB filtering stubs to generate two decoupling nulls. For Ka-band decoupling, the low-band (LB) antenna is loaded with T-shaped branches, a ring resonator, and LB filtering stubs at different layers to introduce three decoupling nulls. High cross-band isolation is realized through the superposition of these decoupling nulls in the K and Ka bands. The proposed shared-aperture antenna achieves cross-band isolation exceeding 38 dB over 19.6–21.2 GHz and 29.4–31 GHz, with an element profile of 1.9 mm, and the phased array supports wide-angle beam scanning up to $\boldsymbol {\pm 60^{\circ } }$ in both bands.