Study of the Input Cavity Characteristics With Two-Beam Loading for Developing a Compact and High-Power Ka-Band Klystron

Abstract

Input cavity characteristics with a two-beam loading are one of the most important scientific problems for using a two-beam scheme to develop compact, high-power millimeter-wave klystrons. This article focuses on this problem with a 400 kW two-beam loading in an overmoded input cavity which is proposed to develop a Ka-band klystron with peak power toward 150–200 kW. The input cavity exploits TM13 mode to support two equivalent sections of field gaps for modulating two beams. The beam loading parameters, such as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{t}$ </tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{b}$ </tex-math></inline-formula> , and cavity parameters, such as electric field distribution, frequency ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f}$ </tex-math></inline-formula> ), and cavity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{l}$ </tex-math></inline-formula> without beams can be optimized and selected to achieve matching absorption by two beams with a certain RF power injection in the Ka-band. The CST Studio Suite (CST) simulation results show that over 99% power of the input signal around 35 GHz can be absorbed by the input cavity loaded by two beams with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{t}$ </tex-math></inline-formula> of 0.473– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.716~\mu \text{P}$ </tex-math></inline-formula> . Constant <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{t}$ </tex-math></inline-formula> exercises about the same degree of two-beam loading on the input cavity.