Input coupling systems for millimetre‐wave gyrotron travelling wave amplifiers

Abstract

Input couplers for millimetre-wave gyrotron travelling wave amplifiers are presented in this study. A W-band input coupling system composed of a pillbox window, a smoothly curved waveguide bend, a T-junction and a broadband reflector was numerically optimised, constructed and measured. An average transmission coefficient of -2.0dB over a designed operating frequency range was measured. Additionally, a higher-frequency input coupler for operation at a central frequency of 372GHz was also designed based on a multiple-hole coupling configuration. The simulated transmission coefficient was -0.5dB if the ohmic loss is not considered.