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

Journal article, 2021

This paper presents a novel microfabrication technique to manufacture gap waveguide components operating at sub-millimeter 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 non-vertical sidewall, non-uniform surface, and time-consuming fabrication process. The proposed dry film photoresist offers significant amount of benefits such as fewer processing steps, reduced production cost, shorter prototyping time over existing micromachine techniques. To validate the proposed fabrication method, SUEX dry film photoresist is used to demonstrate three gap waveguide transmission lines. Different transitions from rectangular waveguide (RW) to gap waveguide (GW) have also been designed to characterize the newly fabricated gap waveguide components with a standard measurement setup. All the designed and fabricated device operates from 220 GHz 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 dB/mm and 0.075 dB/mm for groove gap waveguide and ridge gap waveguide 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.