Design and Simulation of Input & Output Couplers for high power Helix slow wave structure TWT

In this paper, the input and output couplers are designed and simulated for a frequency range of 14.9 to 15.4 GHz Ku-band over 1 kW power. The input coaxial coupler section comprises of an impedance transition with the coaxial ceramic window of 99.5% alumina to handle the maximal input power less than 1 watt. In the output coupler, coaxial to waveguide (WR-62) progression is used to handle the maximal power from the TWT. Initially, the couplers are designed theoretically. Further, the designs are optimized by commercially available 3-D electromagnetic simulation software, micro-wave studio (MWS), computer simulation technology (CST). The Eigen mode simulations for both the couplers give the voltage standing wave ratio (VSWR) value of less than 1.20.