Research On Miniaturized Multilayer Microwave Filter

With the rapid development of modern wireless communication technology,microwave filters require characteristics such as high performance,miniaturization and low cost.This dissertation does a lot of work on multilayer technologies for modern microwave filter.Several kinds of miniaturized multilayer microwave circuit structures,such as broadside-coupled structure and multilayer substrate integrated waveguide?SIW?structure,are deeply explored.By taking use of these new structures for design and research on the high-performance microwave filter,a kind of ultra-wideband?UWB?and dual-wideband bandpass filters?BPF?using multilayer boradside-coupled structures,as well as a dual-band BPF using multilayer circular SIW cavity,are proposed.The dissertation is summarized as follows:Firstly,this dissertation introduces how to design lowpass prototype filters by using insertion loss method,and realization methods of the Butterworth filter,the Chebyshev filter and the Zolotarev filter.After a brief analysis of the principle theory of the odd-even mode,the resonance characteristics of the stepped-impedance resonator?SIR?and stub-loaded resonator?SLR?are discussed.Designs of the multilayer microwave filter,which are proposed in the next chapter,indicate that the computing theories are correct.Secondly,the basic structure of the broadsied-coupled transmission line is introduced,and the transmission characteristics of the microstrip-slot-microstrip broadside-coupled structure,as well as the extraction method of the coupling coefficient,are fully analyzed by constructing the odd-even mode equivalent circuits.In addition,this dissertation clarifies the calculation process of the S parameter of the multisection cascaded coupling structure through the simulation of HFSS,advantages and flaws are given as well.Thirdly,based on the multilayer broadside-coupled structure,an ultra-wideband BPF using microstrip-slot-microstrip broadside-coupled structure,a dual-wideband BPF based on half-wavelength SIR and coplanar waveguide multimode resonator?CPW-MMR?structure,as well as an ultra-wideband BPF using a kind of improved bent T-shaped broadside-coupled transition are proposed,respectively.The correctness of the design method is verified through HFSS simulation and physical measurement.All three types of filters have good circuit performance,and they are easy to realize miniaturization and integration due to their multilayer structures,indicating that broadside-coupled structure is an ideal structure for design on the high-performance microwave filters.Finally,the basic structure of the circular SIW cavity is introduced and some fundamental characteristics,such as the transmission mode and the equivalent condition as the rectangular waveguide,are researched.Besides,the corresponding relationship between two dominant transmission modes(TM₀₁₀ andTM₁₁₀ modes)of the circular SIW cavity and the dimension parameters is obtained,the coupling principles between two multilayer SIW cavities is introduced at the same time.Based on the multilayer circular SIW cavity,a dual-band BPF is designed,which has good circuit performance and both two passbands belong to narrow band.