Filter Design And Optimization Based On Coupling Parameter Ectrcation And Spatial Mappping

With the rapid development of modern wireless communication technology,the working frequencies of microwave communication,television broadcasting,radio navigation and other microwave technologies are increasingly rich,and the existing communication frequency band resources are increasingly limited.Because of its frequency selection characteristics,microwave filters can use frequency resources more efficiently,so its development has been paid more and more attention.The spatial mapping method is widely used in the optimization design of microwave filters because it requires fewer electromagnetic simulations and faster convergence speed.The traditional spatial mapping method requires the establishment of rough circuit model and fine electromagnetic simulation model respectively,which requires the circuit model and electromagnetic model to have the same physical size,and obtains the electromagnetic model corresponding to the optimal circuit model through the spatial mapping of physical size,and completes the optimal design of the filter.When the circuit model corresponding to the physical size of the electromagnetic simulation model is not readily available,the physical size-based spatial mapping method will encounter difficulties.In this paper,the coupling parameter extraction is combined with the spatial mapping method,the physical size parameters of the filter are converted into coupling parameters by the coupling parameter extraction method,and the coupling filter optimization design methods such as coaxial cavity filter and microstrip open-loop filter are realized by combining the spatial mapping method,the main content is summarized as follows:1.For the coaxial cavity filter,multi-port simulation technology is used to calculate the filter coupling parameters through multi-port admittance parameters,which saves the step of establishing an equivalent circuit model compared with the coupling parameter extraction method based on the circuit model,and no longer needs to select a suitable algorithm for filter response fitting,which simplifies the coupling parameter extraction of the cavity filter and improves the filter design efficiency.2.For microstrip open-loop filters,the compact layout reduces the overall volume of the filter,but also leads to poor isolation between resonant loops,resulting in strong non-ideal couplingparasitic coupling,which has a greater impact on filter performance.In this paper,by establishing a multi-port electromagnetic model,the S-parameter(scattering parameter)file with adjustable frequency of each resonant ring is obtained,and the resonant frequency of each resonant ring in the S file is optimized by the circuit simulation software to meet the design indicators,at this time,the coupling matrix corresponding to the circuit model is a modified ideal coupling matrix containing parasitic coupling,compared with the direct application of the ideal coupling matrix for filter design,the corrected coupling matrix is more consistent with the actual situation,and the efficiency of designing the filter is higher.3.Combined with HFSS software and Matlab software,a GUI interface is designed to parameterize some repeated operation steps,realize the automatic modeling of cavity filters and the automatic update of design parameters in the iterative process,reduce the possibility of errors,and save manpower and material resources.