Research Of High-order Topology Of Cavity Filter

The rapid development of mobile communication technology has constantly changed people’s lifestyle and greatly facilitated people’s lives.Mobile communication requires the use of communication devices such as base stations and satellites.Microwave filter is a kind of mobile communication device.Its’ performance will directly affect the quality of the entire communication link.With the promotion of the fifth-generation mobile communication system,the number of base stations will increase significantly,which poses strict requirements on the production capacity of filters.The tuning of microwave filters is a relatively time-consuming part of the research and development process,and it requires the cultivation of a large number of experienced tuning workers.In order to improve the production capacity and reduce costs,computer-aided tuning has become an important part of filter tuning.Due to the existence of parasitic coupling and other reasons,filter’s topology may change from the initial conventional topology to unconventional topology during the tuning process,which is one of the challenges faced by computer-aided tuning.The main work is to study the theory which is related to computer-aided tuning.Based on similarity transformation,the coupling matrix of unconventional topology is solved by analytic method,and the computer-aided tuning program for filters is designed based on Cauchy method and preprocessing technology.First,the generalized Chebyshev filter polynomial synthesis is reviewed,and the N+2 coupling matrix of the filter’s transverse topology is extracted.Taking some classical topologies as examples,the elimination process of the coupling matrix is explained in detail,that is,how to get the target topology through a series of similarity transformations.The optimization algorithm of coupling matrix is studied,the application of homotopy in coupling matrix theory is introduced.Additionally,this thesis has presented an analytical method for solving the coupling matrix corresponding to irregular topology.To validate the effectiveness of the proposed analytical method,the response of the coupling matrix with is compared with the response of polynomial.The advantages and disadvantages of the analytical method are compared with the homotopy method.Then,the principle of extracting filter polynomial by Cauchy method is described.Based on Cauchy method,how to extract Q value of filter and how to remove noise of filter by Cauchy method and preprocessing technology are studied.How to remove loading phase by genetic algorithm is also introduced.Finally,based on the Cauchy method and preprocessing technology,a computer-aided tuning program for filters is designed on the platform of MATLAB GUI.The effectiveness of the computer-aided tuning algorithm is verified by a symmetric filter simulation model and an asymmetric filter full-wave simulation model,which are based on the simulation of MATLAB and CST.