Research Of Millimeter Wave Mode Generator

As we known, the operating mode of the gyrotron is generally TEoi mode or higher order circularly polarized TEmn mode. In practical application, we need to design mode generator to measure the performance of frequency system of gyrotron in the cold test, such as the Q value and frequency of the resonator, transmission and reflection characteristics of the output window, etc. The thesis according to different operation modes of gyrotron, made a comprehensive in-depth theoretical study and numerical simulation of waveguide modes converter and quasi-optical mode generator, the designed generator has been successfully applied to the Department of scientific research and experiments. The main work of this paper is as follows:1, According to the microwave transmission system in the basic characteristics of guided waves and the characteristics of the transmission system, using the circuit knowledge, were designed based on three different mechanisms rectangular TEio to rectangular TE20 mode generators.2, Use of irregular rectangular waveguide mode coupling theory and the perturbation theory design rectangular TE20 to circular TE01 mode generators.3, For the three bands of rectangular TE10 to circular TE01 mode exciter overall simulation and optimization, get excited circular waveguide TE01 mode conversion efficiency were 99.03%、99.12%、98.68%, respectively.4, Through microwave dark room near field test platform and the vector network analyzer for three band of the TE01 mode generator to physical test. Experiments show that the test results and simulation results have good consistency.5, According to the selected mode of coaxial resonator, write a Matlab program to calculate the mode of eigenvalue and the ratio of inside and outside radius of coaxial cavity, to determine the suitable inner and outer radius. Based on non-uniform string equation and boundary condition, write the Matlab program to determine the three sections of resonator cavity structure size. According to the quasi-optical transmission theory and geometrical optics theory, we design a quasi-optical TE61 mode generator, the mode purity is 90.55% at 94.2 GHz.6, According to the radius tapered coupled wave theory, we design an TE61 to TE62 mode converter, the conversion efficiency is 98.92% at 94.2 GHz.7, Quasi-optical TE62 mode generator consists of quasi-optical TE61 mode generator and TE61 to TE62 mode converter, the purity of circularly polarized TE62 mode is 90.03% at 94.2 GHz.