Input/Output System for Millimeter Wave Gyro-TWT

Abstract

In this paper, an input coupler and an output window for TE01 mode millimeter wave gyro-TWT is presented. A 5-slots wrap around mode convertor for converting a rectangular TE10 to circular TE01 mode along with the pill-box window is discussed. The pill-box window is used to seal the vacuum inside the gyro-TWT at the input end. The design of the input coupler is optimized by numerical simulation using CST to get minimum reflections, maximum transmission with large bandwidth and high mode purity. The CST simulation results predict that the input coupler offers a good transmission (> -0.5 dB) and low reflection (< - 32 dB) at the operating frequency of 92 GHz. Further, a three-disc output window is designed and simulated to seal the vacuum inside the gyro-TWT at the output end. The ceramic material Al2O3 due to its high mechanical strength is used. The output window has a reflection coefficient less than -15 dB for 85 – 100 GHz bandwidth.