Highly Selective Dual-Polarized Filtering Antenna Based on Inline Coupling Topology

A dual-polarized filtering antenna possessing high-frequency selectivity is proposed. It consists of five rectangular air-filled cavities stacked on top of each other and two stripline feed structures. The adjacent cavities are coupled through slots, except for the second and third cavities from the bottom, which are excited by the probes extended from the Y-shaped stripline. The cavity at the top radiates through two pairs of parallel slots, implementing an inline coupling topology. Unlike traditional inline coupling topology, two radiation nulls are generated by placing the source node between the resonant nodes. The skirt selectivity of the filtering antenna is improved without utilizing cross-coupling. Dual-polarization is achieved by benefiting from the modal orthogonality of the TE101 and TE011 modes in a single cavity, and two truncated cones are introduced to improve the interport isolation. For proof-of-concept demonstration purposes, a dual-polarized fifth-order filtering antenna is fabricated and measured. The measured reflection coefficient is greater than 10 dB in the range of 9.913-10.087 GHz, and a measured peak gain of 8.7 dBi is obtained. Two radiation nulls occur at 9.91 and 10.098 GHz.