Research Of Multilayer Multi-passband Filter

With the rapid development of communication technology,more and more communication equipment requires that the communication system can simultaneously process signals in several frequency bands so that the signals can be selected and transmitted.Therefore,multi-passband filters have become an important requirement in the industry.Spectrum resources are becoming increasingly shortage,and multi-passband filters can improve its coefficient of utilization,so research on multi-passband filters becomes very important.The traditional design method of a multi-passband filter is to design multiple single-passband filters,and then employing the common ports and matching circuit.However,this method will increase the circuit size of the filter,which is not satisfactory conducive to miniaturization.The multi-layer structure can make full use of the top and bottom space of the dielectric substrate,which can help to reduce the overall size of the circuit.This thesis aims to propose a multi-passband,miniaturized,high-performance filter using split ring resonators(SRR),stub-loaded resonators(SLR),stepped impedance resonators(SIR),microstrip-CPW broadside-coupled structures,CPW-stripline transition structure,defected microstrip structure(DMS),cross-coupling structure and several other structures.The main contents of this thesis are as follows:(1)Several methods to realize the multi-passband filter is introduced,and the working principles of SLR and SIR are analyzed.Besides,this thesis focuses on the analysis of the variation trend of the odd and even mode resonant frequency of SLR with the circuit parameters..(2)The realization method of miniaturization is introduced,focusing on the analysis of SRR method and its related multilayer structures,which include multilayer broadside-coupled structure,multilayer structures consisting of several transition structures,and so on.The equivalent circuits of these multilayer structures are established and their calculation methods are analyzed.(3)Two types of single-layer filters are proposed and fabricated: the ultra-wideband and the triple-band filters based on SIR structures.(4)Three multi-layer multi-passband filters are proposed and fabricated:(1)A compact dual-band bandpass filter based on OSLSRR;(2)A dual-band bandpass filter based on the microstrip-coplanar waveguide(CPW)broadside-coupled structure;(3)dual-band bandpass filter based on CPW-stripline transition structure,these three filters have realized the performance of dual-band,miniaturization and high out-of-band suppression.