Design of a Novel Dual-Band Gyro-TWT

Abstract

The design of a novel dual-band (Ku/Ka) gyrotron-traveling-wave tube is presented in this paper. As the gain per-unit of the Ku-band is lower than Ka-band’s, three special methods have been adopted: 1) the two input couplers are separated in space; 2) the magnetron injection gun magnetic compression ratio of the Ku-band is greater than Ka-band’s; and 3) the Ku-band beam current and velocity ratio are greater than Ka-band’s. Wall resistivity is employed to suppress the potential spurious competing modes. The 3-D particle-in-cell simulation predicts a maximum output power of 238/158 kW, maximum gain of 45.5/50.4 dB, and 3-dB bandwidth <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 2.1$ </tex-math></inline-formula> /3.4 GHz, respectively, for Ku-band and Ka-band. After careful optimization and under a compromise consideration, the output window is also designed to ensure the device has a bandwidth of 1.5/2.5 GHz for Ku/Ka-band with a peak power >100 kW.