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Low-Loss Gap Waveguide Transmission Line and Transitions at 220–320 GHz Using Dry Film Micromachining

This article presents a novel microfabrication technique to manufacture gap waveguide (GW) components operating at submillimeter-wave (sub-mmWave) frequency range. The conventional metal waveguide component manufacturing has a low resolution and low throughput and is not suitable for applications above 100 GHz. The micromachining techniques have matured and applied in various applications. Several micromachining techniques have been developed to address the specification requirements of different fields. Conventional micromachining techniques suffer from fabrication issues, such as nonvertical sidewall, nonuniform surface, and time-consuming fabrication process. The proposed dry film photoresist offers a significant amount of benefits, such as fewer processing steps, reduced production cost, and shorter prototyping time over existing micromachine techniques. To validate the proposed fabrication method, SUEX dry film photoresist is used to demonstrate three GW transmission lines. Different transitions from rectangular waveguide (RW) to GW have also been designed to characterize the newly fabricated GW components with a standard measurement setup. All the designed and fabricated devices operate from 220 to 320 GHz. The fabricated devices showed a good agreement with the simulation result over this frequency band and the measured average insertion losses were in the order of 0.048 and 0.075 dB/mm for groove GW and ridge GW, respectively. Thus, dry film photoresist provides fabrication precision of the structures and consequently opens the path for low-cost fabrication of high-frequency waveguide components.