3-D Printed Millimeter-Wave Self-Diplexing Filtering Waveguide Antenna With Orthogonal Circular Polarizations

A dual-band self-diplexing filtering waveguide antenna with orthogonal circular polarizations is proposed for millimeter-wave communication systems. The antenna consists of an orthogonal-mode filtering feeding circuit, a dual-band dual-circular polarizer, and a 3×3 radiating aperture array. By utilizing a higher-order mode cavity, a converted cross-coupled topology with all-magnetic coupling irises is realized, achieving high-selectivity filtering channels with advantages of easy fabrication and reduced sensitivity. An orthogonal self-diplexing feeding circuit is then constructed by merging two filtering channels through a pair of dual-mode cavities, eliminating the need for separate orthogonal-mode transducers and diplexers, resulting in a more compact structure. The inherent orthogonality of the electromagnetic fields in the two channels enables flexible operating frequencies, adjustable bandwidth, and natural isolation between the two bands. A shared-aperture technique is adopted with a three-stage stepped-rotated rectangular polarizer integrated into a 3×3 array, efficiently converting dual-linearly polarized (LP) waves in adjacent frequency bands into orthogonal circularly polarized (CP) waves, thus enhancing gain performance. For experimental validation, a prototype was fabricated using all-metal 3-D printing technology, ensuring high integration, precision fabrication, and reduced insertion loss. Measurement results demonstrate effective operation across 28.0-28.9 GHz and 30.0-31.0 GHz, with a small frequency ratio of 1.07 and measured radiation gains of 13.3 dBic and 13.2 dBic, respectively. The proposed antenna’s multifunctionality, compact integration, and low loss position it as a promising solution for advanced millimeter-wave communication systems.