Research On The Characteristics Of Dual/Multimode Resonators And Their Applications In Filters

With the rapid development of modern science and technology,modern microwave wireless communication systems or radar systems have proposed higher requirements for miniaturization,high integration,low loss,multi-function and many other specifications.Recently how to realize the high performance filter with compact size,low insertion loss and low cost has attracted researchers in related fields to research it because the filter is a key component in various microwave circuit systems.The concept of dual/multimode resonator means there are two or more operating resonant modes in a single resonator.The advantage of this concept is that it can be used to realize the dual/multiple transmission pole filtering response without adding additional resonators,so the concept provides a way to realize the miniaturization for filters.Based on this concept,the resonant characteristics of dual/multimode resonators using microstrip patch,Substrate Integrated Waveguide(SIW)and 3D printed cavity technologies are studied carefully in this dissertation.Meanwhile,the application and advantages of mentioned resonators for filter design are further explored.The dissertation main content can be summarized as the following four parts:Firstly,to solve the problem of large size of traditional dual/multimode microstrip patch resonators and additional radiation loss caused by slot-line loaded microstrip patch resonators,a dual-mode sector microstrip patch resonator and a quad-mode rectangular microstrip patch resonator both with metallic via-hole perturbation are proposed in this dissertation.Due to its own structural characteristics and adding metallic via-hole perturbation,the sector microstrip patch resonator can achieve further miniaturization.Adjustment freedom degree of the overall rectangular microstrip patch resonator is increased by adding stubs.The calculation formulas of the resonant frequencies of the proposed two resonators are also derived by electromagnetic field theory and odd-even mode theory,respectively.In order to verify the above conclusions,a single bandpass filter and a dual-band bandpass filter are designed by using dual-mode sector microstrip patch resonator with metallic via-hole perturbation,and a dual-band filter is also designed by using four-mode rectangular microstrip patch resonator with metallic via-hole perturbation.The test results verify the feasibility of miniaturization for filters based on the proposed resonators.Secondly,in order to realize the miniaturization of a single SIW resonator,a sector SIW resonator with a minimal angle of apex is proposed in the dissertation,and the calculation formula of the resonant frequency of this resonator is given by the electromagnetic field theory.In order to solve the weakness of low adjustment freedom degree of the conventional half-mode SIW resonator,a rectangular half-mode SIW resonator with stubs is proposed.To verify the above results,an ultra-wideband bandpass filter and a dual-band filter are designed based on the above resonators.The test results show that the two filters achieve miniaturization and also verify the feasibility of the proposed method for realizing the miniaturization of the resonator and filter.This dissertation also makes a supplement to the existing research on circular ring resonators,and the resonant characteristics of circular ring resonators with three different boundary conditions including outer magnetic wall inner electric wall,outer electric wall inner magnetic wall,and outer electric wall inner electric wall are studied in detail.The expressions of the field components,resonant frequency and unloaded quality factor of each mode of the three types of circular ring resonators under certain conditions are derived in detail by using electromagnetic field theory.The correctness and scope of application of the analytical expressions are verified by comparing the simulated and calculated results.Then,to solve the problem of designing dual-passband and multipassband filters using a single SIW resonator on the basis of the above conclusions,three improved resonators based on the circular ring resonator are proposed in this dissertation:a circular ring half-mode SIW resonator with stubs,a stepped impedance circular ring SIW resonator,and a sector ring half-mode SIW resonator.Two dual-passband filters and one four-passband filter are designed based on these three resonators.The test results verify the feasibility of implementing multi-band filters based on a single sector ring halfmode SIW resonator.And this study also provides three realizable methods for designing dual-band and multi-band filters based on a single SIW resonator.Finally,in order to solve the problem of realizing lightweight of traditional metal waveguides and reducing the radiation loss caused by partial assembly and achieving the miniaturization of traditional hollow spherical resonators,two kinds of dual/multi-mode nested spherical resonators fabricated by monolithic stereolithography apparatus(SLA)3D printing technology are proposed and studied carefully.Firstly,a nested spherical resonator with a single metal sphere inside is proposed and analyzed,and the miniaturization advantage of the proposed resonator is verified by comparing it with the traditional hollow spherical cavity resonator.Three kinds of bandpass filters are designed by using single-mode and three-mode nested spherical resonators based on the above discussion.Then,an improved dual-mode nested spherical resonator is proposed based on the above resonator,and a dual-mode dual-band filter is designed based on this resonator.The test results show that all the filters based on the aforementioned resonators realize miniaturization.Compared with the existing reports and literatures,the further miniaturization has been significantly achieved.In summary,the resonant characteristics of three types of dual/multimode resonators are carefully studied and their filter applications and miniaturization advantages are also given.Therefore,the studies in this dissertation have high research significance and engineering value and a wide application prospects in modern microwave/millimeterwave circuit systems.