Design of Compact and Easy-to-Fabricate Power Coupling Structures for Sub-Terahertz Sheet Beam Traveling Wave Amplifiers

The great challenge in fabrication is one of the most significant factors for hindering the development of subterahertz sheet beam traveling wave amplifiers (SB-TWAs). Therefore, it is in great demand to develop power coupling structures and slow wave structures with easy-to-fabricate and compact geometries for SB-TWAs. In addition, it is desirable that their heights are as small as possible, thus conducive to the focusing of the sheet electron beam. In this article, two novel power coupling structures are designed, which are based on an H -plane short-slot and multiple branch waveguides, respectively. The former one is highlighted by its compactness, and the latter one has a wider frequency bandwidth. Two proof-of-concept prototypes of the proposed power coupling structures were microfabricated and tested, showing excellent agreement between experimental measurements and design simulations. Reflection coefficient <-13.6 dB, isolation coefficient <-15.4 dB, and transmission coefficient >-2.2 dB were experimentally obtained across the band of 220.0-273.4 GHz (53.4 GHz). Hopefully, a wider measured frequency bandwidth will be obtained if the operating frequency range of the vector network analyzer could be extended to lower frequencies.