Ku-Band Monolithic Magic-T Using a Hexagonal Waveguide Fabricated by Metal Additive Manufacturing

Abstract

This paper presents the design and development of a Ku-band magic-T based on a hexagonal waveguide (HWG) fabricated using metal additive manufacturing. Instead of a conventional rectangular waveguide (RWG), an HWG that is well suited for metal additive manufacturing was introduced, and analytical formulations were derived to predict multiple electromagnetic characteristics of the proposed HWG. To enhance the single-mode operating bandwidth, a double-ridged hexagonal waveguide (DR-HWG) was proposed. HWG-based shunt inductive and capacitive iris structures were also designed, analyzed, and subsequently incorporated into the magic-T design. Finally, a Ku-band monolithic HWG-based magic-T was designed and fabricated, including HWG-to-RWG transitions for measurement compatibility. The fabricated back-to-back inline transition exhibited a return loss better than 18 dB and an insertion loss below 0.1 dB across the entire Ku-band. The fabricated HWG-based Ku-band magic-T achieved a return loss better than 15 dB over 14.1–16.0 GHz, an insertion loss below 0.3 dB, and isolation levels exceeding 43 dB at the output ports and 20 dB at the input ports. The fabricated HWG-based Ku-band magic-T achieves low insertion loss, high port-to-port isolation, and a wide operational bandwidth. These experimental results confirm that the proposed HWG architecture is well suited for realizing high-performance monolithic waveguide components fabricated by metal additive manufacturing.