H - and E -Plane Loaded Slow Wave Structure for W -Band TWT

Sheet beam vacuum electron tubes are an attractive solution for high-power sources or amplifiers at millimeter-waves. In this article, a novel ${W}$ -band slow wave structure (SWS) for traveling wave tube (TWT) amplifiers supporting a sheet beam is proposed. The SWS is based on a rectangular waveguide with ${H}$ - and ${E}$ -plane loaded (HEL) metal corrugations. A test structure of the proposed HEL SWS with purposely designed input and output couplers was built in the frequency range of 91–98 GHz ( ${W}$ -band). The measured scattering-parameters agree well with the simulations showing ${S}_{11} dB over 10-GHz bandwidth. A TWT was designed and simulated with the HEL SWS. It shows very good gain-bandwidth performance. The SWS is easy to manufacture by low-cost computer numerical controlled (CNC)-milling. The results demonstrated that the HEL SWS is a very good solution to build high-power, wideband millimeter-wave TWTs for a wide range of applications that need high power in a broad frequency range.