3D-Printed Metallic 90 • Bent Ridge Gap Waveguide Structures: Enabling Compact Antenna and Passive Component Integration in CubeSats

This letter presents, for the first time, the feasibility and potential of fully metallic 3D-printed technology for the implementation of 90 • bent ridge gap waveguide (RGW) structures that are unachievable through conventional milling due to their three-dimensional complexity. Experimental validation is provided through the realization of two components: a narrowband, highly isolated 90 • bent 4-port RGW-based waveguide bend and a compact slot antenna with an integrated 90 • bend, both tailored for compact CubeSat integration. Designed for millimeter-wave (mmWave) Internet of Space (IoS) applications operating between 26 and 28 GHz, the waveguide bend achieves a reflection coefficient between-10 and-20 dB, insertion loss between 1 and 2 dB, and port-to-port isolation exceeding 40 dB. The antenna operates from 27.3 to 28 GHz, achieving a maximum realized gain of 5 dBi and a radiation efficiency of 78%. Beyond demonstrating the feasibility of metal additive manufacturing for complex RGW geometries, the proposed structures offer substantial benefits in footprint reduction, integration flexibility, and structural robustness. These advantages make them strong candidates for next-generation high-density CubeSat RF subsystems.