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.

This paper presents a novel micromachining process to fabricate a 140 GHz planar antenna based on gap waveguide technology to be used in the next-generation backhauling links. The 140 GHz planar array antenna consists of three layers, all of which have been fabricated using polymer-based microfabrication and injection molding. The 140 GHz antenna has the potential to be used as an element in a bigger 3D array in a line-of-sight (LOS) multiple input multiple output (MIMO) configuration to boost the network capacity. In this work, we focus on the fabrication of a single antenna array element based on gap waveguide technology. Depending on the complexity of each antenna layer’s design, three different micromachining techniques, SU8 fabrication, polydimethylsiloxane (PDMS) molding, and injection molding of the polymer (OSTEMER), together with gold (Au) coating, have been utilized to fabricate a single 140 GHz planar array antenna. The input reflection coefficient was measured to be below − 11 dB over a 14% bandwidth from 132 to 152 GHz, and the antenna gain was measured to be 31 dBi at 140 GHz, both of which are in good agreement with the simulations.