Compact Dual-Broadband Dual-Polarized Shared-Aperture Horn Antenna Based on Nested Gap Waveguide Turnstile Junction OMTs

This paper presents a novel compact dual-broadband dual-polarized shared-aperture horn antenna based on gap waveguide modules, covering the entire W- and Ka-bands with a frequency ratio of 2.8:1. The antenna consists of two nested groove gap waveguide (GGW) turnstile junction orthomode transducers (OMTs) and a dual-band heterogeneous shared-aperture antenna combining a high-band dielectric rod and a low-band conical horn. Two OMTs employ a circular waveguide and a coaxial waveguide as their common ports, respectively. Both OMTs achieve simulated return loss (RL) exceeding 25 dB, insertion loss below 0.1 dB, and isolation better than 40 dB over 26.5–40 GHz (40.6%) and 75–110 GHz (37.8%). These results highlight significant advantages over previously reported band-gap OMTs. All components, except for the dielectric rod, are integrated into four layers of GW modules, resulting in an overall antenna with fewer building blocks and a low-profile design, with the nested dual-band OMTs featuring an ultra-low profile of 1.4λ0. A prototype was fabricated and tested to validate the performance of the proposed antenna. The measured results closely match the simulations, with RL exceeding 13.5/15 dB and isolation better than 40 dB within 26.5–40 GHz and 75–110 GHz, and dual-band dual-polarized gains exhibiting an approximate level of 16±3 dBi. The proposed antenna module offers advantages such as multi-broadband dual-polarized operation, low profile, and high integration. Based on the proposed architecture, the antenna operating bands can be extended to three or more full bands, with only one additional building block required for each extra band.