Calculation And Analysis Of Characteristic Parameters For Lossy Resonator

As one of the basic components in the structure of modern industrial microwave devices,microwave resonators play an important role in determining the performance of devices.In practical applications,the cavity walls are usually coated with various loss media to satisfy the design requirements.Therefore,the analysis of the characteristic parameters of such resonators has significant application value and theoretical significance.With the deepening of theoretical and practical research,various kinds of new loss media have been developed in rapid succession.How to efficiently realize the calculation and analysis of the characteristic parameters of the resonator loaded with multiple kinds of loss media has become the research focus of high-performance microwave device design.Based on the basic model of a resonator coated with multilayer lossy media,this paper analyzes and discusses the effects of permittivity,magnetic loss coefficient,number of coating layers,position and thickness on the different mode characteristics of the electromagnetic field inside the resonator.Mode matching method is used for establishing a matching relationship at discontinuities through the equivalence of tangential fields.The following aspects are mainly accomplished:（1）This paper introduces and analyzes the solution forms of Helmholtz equation in cylindrical coordinate system,and expounds various cylindrical harmonic function theories characterizing the electromagnetic field forms under different boundary conditions.At the same time,according to the Borgnis function,the electromagnetic field components in the analyzed resonant cavity are determined in r,?and z direction.Based on the expressions,the mode matching method used at the interface and the secant method used to solve the characteristic equation are studied,and the role of the main characteristic parameters of the resonator in the design is clarified.（2）Based on the electromagnetic characteristics of lossy media,an approximate expression of the field components of the TM_0i mode in a lossy resonant cavity is established using the Borgnis function method in consideration of a single layer of lossy medium.The characteristic equation is obtained at the interface using the mode matching method,thereby obtaining a general expression for calculating the resonant frequency and quality factor of the TM₀₁₀ mode.Based on this model,the electromagnetic characteristics of a lossy resonator coated with dielectrics at both ends and a lossy resonator coated with magnetic lossy media at the side are calculated and analyzed.The influence of the thickness,location,and types of the loss media on the electromagnetic resonance characteristics are explored,and the physical mechanism is analyzed and explained.（3）Based on a lossy resonant cavity with multiple layers of electrical and magnetic loss materials,the characteristic equation in the condition of lossy medium mutation is obtained through this calculation method,and the influence of structure and dielectric parameters on resonant frequency and quality factor Q is analyzed.The results show that both electrical and magnetic lossy medium layers can effectively change the resonant characteristics of the TM₀₁₀ mode in the resonant cavity.The loss angle of the magnetic lossy material coated on the side wall significantly changes the quality factor of the resonant cavity,and the thickness of the electrical loss material coated on the upper and lower ends significantly affects the frequency of the resonant cavity.The fusion of the two materials in different positions of the resonant cavity can effectively achieve the coexistence of multiple design objectives.Moreover,the calculation results are in good agreement with the simulation results of the CST-MWS solver,proving that the algorithm is effective in solving the analysis and calculation of resonant cavities loaded with multi-layer lossy media.It provides a certain theoretical reference value for the theoretical analysis of resonant cavities loaded with loss media and the application of TM₀₁₀ mode in microwave devices.