New Analytical Synthesis Technique For Microwave Filter Devices

With the development of science and technology,mobile communication technology and wireless communication technology are constantly updated,and the requirements for microwave filters are more stringent.The so-called analytic synthesis of filter components is to determine the topological structure of the filter and the ideal parameters of the related components,so as to pave the way for the subsequent processing and measurement of the filter devices.In this paper,three aspects are studied,including the analytical synthesis of filters with arbitrary reference impedances,filters with mixed topology and in-line diplexers.The main contents of the paper are as follows:1.A general synthesis approach of coupling matrix with arbitrary reference impedances,that is introduced in general S_{1 1} and S₂₁ characteristic functions.So that the synthesized filter can be loaded with arbitrary reference impedances.Compared with the normalized filter,there is no need for additional matching network to reduce the size of the RF front-end.2.In the analytic synthesis of mixed topological filter,the structure of non-resonant node is introduced.The non-resonant node can realize pure imaginary finite transmission zeros,and make the group delay in band more flat.At the same time,a mixed topology including both non-resonant node structure and cross-coupled structure is introduced.The mixed topology combines the advantages of the two structures to achieve flexible control of transmission zeros.3.In the analytical synthesis of in-line diplexer,frequency-variant couplings?FVC?is introduced.FVC is obtained by matrix transformation of CT structure.Firstly,the BOX structure is obtained by similarity transformation of CT structure,then the scaling transformation of BOX frequency variable,and finally the FVC structure is obtained by similarity transformation of BOX structure matrix.