Research On High Performance Filter Based On Planar Integration And Hybrid Mode

Information technology has been developed explosively in recent years,and the demand for RF filters in RF communication systems has increased.In the face of the scarcity of spectrum resources and the decreasing size of communication equipment,the characteristics of high steepness,miniaturization,and wide stopband are demanded for today's high-performance planar filters.As the representative of high Q value and high integration in planar filters,substrate integrated waveguides(SIW)have been widely used in the design of microwave filters in recent years.But SIW itself has the characteristic of large size.Other planar resonators,such as microstrip resonators have the advantages of small size and high design flexibility,but they are accompanied by significant loss and other defects.Therefore,this thesis aims to study how to improve the performance of the planar filter,get miniaturization,a wide stopband,and design high flexibility response.This paper begins with an overview of the development of planar microwave filters,followed by an explanation of the basic theory of microwave filters and a review of the design process of coupled filters.This paper then presents a structural and modal analysis of common planar resonator structures(SIW cavities,microstrip resonators and mushroom-like resonators).The characteristics of these types of planar resonators and their operating principles are described separately,laying the theoretical foundation for the filter examples designed later in the thesis.Then two mixed-mode multiband filters are introduced in this thesis,a triple-band filter based on SIW and a dual-band hybrid filter based on SIW.The first six modes(TE₁₀₁,TE₁₀₂,TE₂₀₁,TE₂₀₂,TE₃₀₁ and TE₄₀₁)of the rectangular SIW cavity are analyzed,and the frequency of these modes changing with the aspect ratio of the rectangular cavity is studied,based on which the filter response with high steepness and strong suppression ability is designed.Both filters utilize multiple modes of the SIW cavity and employ cavity stacking to achieve a compact size.Finally,two hybrid structure filters are designed:shielded QMSIW(Shield-Quarter-Mode Substrate Integrated Waveguide,S-QMSIW)and microstrip resonator hybrid structure filter and filter combined SIW cavity and mushroom-like resonator.The first S-QMSIW and microstrip hybrid filter combine two different types of resonators to form the filter response.This realizes the effect of miniaturization and uses the characteristic that the high-order modes of the two resonators are not resonant at the same frequency to achieve the effect of a wide stopband.The second filter with the hybrid structure of SIW cavity and mushroom-like resonators create a dual-passband response and improve the flexibility of filter design.These two filters will demonstrate the advantages of a hybrid planar filter from two perspectives.