A MISL Crossover-Based Dual-Polarized Filtering Antenna for Millimeter-Wave Applications

Abstract

This letter presents a multifunctional filtering crossover antenna based on the metal integrated suspended line (MISL) technology for millimeter-wave base-station applications. Different from conventional filtering antennas employing separate filtering, feeding, and decoupling structures, the proposed filtering crossover functions as a multifunctional electromagnetic component that simultaneously realizes signal routing, filtering, dual-polarized excitation, and intrinsic port isolation. A quantitative modal-overlap evaluation framework is further introduced to and verify the orthogonality of the degenerate TM$_{110}$ modes. A third-order prototype operating at 29.35 GHz is designed, fabricated, and measured. The measured results show an average gain of 6.76 dBi, a radiation efficiency of 93%, an out-of-band suppression exceeding 20 dB, and a port isolation better than 18 dB. Owing to the all-metal MISL implementation, the proposed antenna also features a compact low-profile structure, making it attractive for millimeter-wave dual-polarized front-end applications.