Te < Sub > N 01 < / Sub > Model A High Q Cavity Multimode Cavity Mode Interference And Purification

The history of using TE_01nmode cylindrical resonant cavity to measure themicrowave complex permittivity of solid dielectric materials can be traced back toforward the fifties and sixties of the last century. Such a cavity, can accuratelymeasuring the loss angle tangent tanδof the low-loss dielectric materials because of itsHigh-Q value. Along the wall, the electric field is zero. The piston has simple structure,excellent performance, non-contact tuning and the small gap between the placeddisc-shaped test sample and the cavity wall has a little impact on the measurement. So itis widely used.The main contents of this dissertation are about the mode interference andpurification research, The High-Q resonant cavity has covered7¹8GHz bandwidth,and in this test cavity, multi-mode TE_01nis existed. On the basis of analysis to therespective electromagnetic fields characteristics, about working modes and interferencepatterns especially the degenerate modes, the cavity has consist of main cavity,back-cavity and the piston. Each parameter index of three parts made systematic designand optimize, and it gets a satisfactory result.In this project, the author did some works as follows:1. Introduce the main test methods for solid dielectric materials to measuring themicrowave complex permittivity. Brief the status and development trends in thedomestic and international research. Explain and expound the professional terms suchas Multi-mode cavity testing technology and the mode purification technology so on.2. Review carefully the basic theoretical knowledges about cylindrical resonantcavity. Focus on the analysis of the modes’ characteristics about TE_01nmode and thedegenerate mode TM_11n. Discuss the effects on the interference patterns especially thedegenerate mode. Study the whole design of the cylindrical resonant cavity, and designfirstly the main cavity.3. The back-cavity processing technology includes absorbing material adding andchoosing G. According HFSS simulation to get the suitable size of G and optimize thepiston parameters including h₁h₂and D₂. With the help of optimetrics module, optimize the h₃of the piston. While ε’=6.7，tanδ=0.5and h₃is13.8mm, the purificationresult is best.4. Make a new cavity, analyse and compare the experimental results and simulationdatas, the result verify the correctness of our optimization design.The test data shows that the theoretical analysis of the paper is correct, and theoptimization design is reasonable, the measurement result has achieved the target whichwe required.