Research On Microwave Passive Frequency Selectivity Circuit Based On Substrate Integrated Waveguide Technology

With the development of microwave wireless communication technology,microwave passive frequency selectivity circuits,which can integrate the functions of filters and other microwave passive components and reduce the entire circuit efficiently,have attracted much more attention.Meanwhile,to meet the multiple communication standards requirements in the modern wireless communication systems,the multi-band research of frequency selectivity circuits has also become an increasingly active branch.As an easy-to-integrate planar circuit,the substrate integrated waveguide(SIW)technology lays the foundation for the design and implementation of high-performance,planar,low-cost,and easy-to-integrate microwave passive circuits.Based on this,this dissertation put forwards a series of wideband bandpass filters(BPFs),diplexers and filtering crossovers.The main research work can be summarized as follows:First,since the SIW wideband BPFs suffer large size and complicated notch design,a series of(ultra)wideband BPFs with superior performances have been proposed by integrating multiple miniaturization technologies: single cavity,cut-SIW and multimode resonant cavity.Firstly,the HMSIW(half-mode SIW)resonator is studied in depth,and a filter with UWB(ultra-wideband)characteristics is designed by combining multi-mode resonator and single cavity technologies;then,based on the miniaturization characteristics of quarter-mode SIW(QMSIW),this dissertation develops a wideband BPF utilizing hybrid structure and single cavity technologies.In addition,CSRRs(complementary split ring resonators)are embedded on the metal surface of the proposed filters to design notched-bands.This method can also be used to design any number of notched-bands with flexibly controllable frequencies.In addition,since SIW dual-band BPFs suffer large size and narrow bandwidth,the characteristics of miniaturization and wideband research are constructed,and a series of filters with superior performance are proposed.First,a dual-band BPF with 3-d B fractional bandwidth(FBW)of 14.7% and12.23% is designed based on SIW multimode resonator,hybrid structure and single cavity technologies.Then,a compact dual-wideband BPF based on a single perturbed SIW multimode resonator is proposed,and its 3-d B FBW has been extended to 48.1% and34.9%.The proposed filters are very suitable for modern single-frequency and multifrequency wideband wireless communication systems.Secondly,since current SIW diplexers suffer single frequency filtering responses,a SIW diplexer with dual-band filtering response is proposed.First,the SIW quadruplemode resonator(QMR)is used as a T-junction.Then,based on the modal orthogonality and frequency selectivity of the QMR,four resonant modes are divided into two groups and transmitted to two ports respectively,thereby realizing two isolated dual-band filtering channels.Compared with traditional SIW diplexers,the dissertation applies the dual-frequency design concept to the SIW diplexers,thereby realizing two filtering channels working at 5.96 GHz & 8.6 GHz and 7.04 GHz & 9.68 GHz with isolation degree better than 15.6d B.Aiming at large size caused by multi-cavity cascade design,this dissertation utilizes a single multimode resonant cavity to realize a SIW diplexer with second-order filtering response for the first time.Compared with the traditional planar SIW diplexers,the size of the proposed diplexer is reduced by more than 50%,and its isolation is better than 15.4 d B.This method has important application value for the size miniaturization of SIW diplexers.Next,since the design method of current SIW filtering crossovers is limited to dualmode resonant cavity and multi-cavity cascade,the SIW quadruple-mode resonator is employed to design a crossover for the first time.Based on modal orthogonality characteristics,a SIW filtering crossover with second-order filtering response is implemented using a single cavity innovatively,and the isolation is better than 14.7 d B.Compared with the traditional planar SIW filtering crossovers,the entire circuit of the proposed filtering crossover is integrated in a single cavity to reduce the size by more than 67.7%.Since current SIW filtering crossovers suffer single frequency responses,this dissertation extends multi-band filtering responses to SIW crossovers.To overcome the difficulty of implementing mode isolation in traditional resonant cavities,a series of SIW multi-mode resonators based on perturbation technology are proposed in this dissertation,and their resonance characteristics are studied in depth.Finally,they are respectively applied to implement dual-band and triple-band filtering crossovers with isolation degree better than 13.5 d B.The proposed SIW multi-band filtering crossovers are very suitable for modern wireless communication systems,which have urgent needs for the number of frequency bands.Finally,two different types of multifunctional circuits are studied in this dissertation.Since current SIW diplexers suffer single working state,a SIW diplexer that can integrate three different working states is proposed.Firstly,the dissertation makes an in-depth analysis of the electric field characteristics of the SIW triple-mode resonator,and then applies the analysis to allocate the input and output ports,so that three diplexers with different working states can be integrated into one diplexer,and the isolation among three working states is better than 12.5 d B.Meanwhile,slots are introduced to control the working frequencies independently.Then,based on SIW triple-mode resonant cavities,a multifunction circuit,which can simultaneously integrate a four-state diplexer and a filtering crossover,is proposed,and the isolation among the five working states is better than 12.7 d B.The proposed multi-function circuits are very suitable for frequency hopping systems and greatly expand the practical application range.