Input coupling systems for terahertz gyro-TWAs

Input coupling systems for THz gyrotron traveling wave amplifiers (gyro-TWAs) are presented in this paper. These form one of the most critical parts of the gyro-TWA as it feeds the low power seed signal into the interaction circuit and incorrect design can lead to cessation of the amplification. The T-junction, multihole and multiarm coupler types were simulated in CST Microwave Studio and their optimized reflection and transmission characteristics, operating at a central frequency of 0.37 THz are presented. A scaled multiarm coupler, designed to then operate at 94 GHz, was manufactured and its microwave properties measured on a vector network analyser.