Coupling Parameter Extraction Of Microwave Filter

Microwave filter is an important frequency selection device in communication systems.Therefore,it has been widely used in almost all microwave communication systems.Especially in recent years,the communications industry has achieved rapid development,and traditional filters can no longer meet the requirements of modern communication technologies,therefore the high-performance complex topology filter has been proposed.However,these high-performance filters either have a higher order or have a complex topology with cross-coupling,which makes the design of the filter relatively complicated.The parameter extraction can quickly extract the coupling matrix of the filter.The coupling matrix,which can guide the design and tuning of the filter,thereby reducing the filter production time and cost,and completing large-scale mass production of filters.The main work of the thesis is to study the theoretical analysis and implementation of coupling parameters extraction of microwave filters with cross-coupling structure.In this paper,we first review the theory of synthesis of microwave filter N×N coupling matrix and focus on the coupling matrix synthesis method for CT/CQ topology filters.Then,the N+2 transversal coupling matrix is extracted,and the coupling matrix of the specified topological structure is extracted by a series of similar transformations of coupling matrix and present the eigenvalue-based gradient optimization method to extract the coupling matrix of an arbitrary topology filter.In addition,an improved Cauchy method for extracting the characteristic polynomial of the microwave filter is proposed,and the S-B algorithm is used to eliminate the influence of noise in the S-parameter frequency response during the sampling process,which increasing the accuracy of the microwave filter coupling parameter extraction.Subsequently,a parameter extraction method suitable for the cross-coupling structure of microwave filters is presented.In the process of parameter extraction,the influence of loading phase and loss is solved,and the hybrid gradient optimization algorithm is used to extract the coupling matrix of the specific topology filter.The detailed process of parameter extraction is described through the waveguide filter and the coaxial cavity filter with CT/CQ topologies structure,which verify the effectiveness of the proposed parameter extraction method.