High Selectivity,Wide Stopband And Frequency Reconfigurable Filter Based On Substrate Integrated Waveguide Resonator

With the depletion of spectrum resources in low frequency band,people turn their attention to millimeter wave and terahertz which have more abundant spectrum resources,followed by increasingly complex functions and higher requirements of electrical performance.Therefore,Substrate Integrated Waveguide(SIW)technology with low loss,high Q value,low cost,high reliability and high power capacity has become a hot research direction.In addition,due to the increasing complexity of wireless communication systems,it is often necessary to integrate as many as dozens of frequency bands in a RF system.This poses a great challenge to the performance and compatibility of passive filters.Therefore,this thesis focuses on the research of the out-of-band suppression technology and the tunable technology of the substrate integrated waveguide,and designs a number of high performance stopband and frequency reconfigurable SIW filters.The main work contents of this thesis are as follows:1.In chapter 2,we summarize and introduce a method of coupling coefficient extraction suitable for SIW.Compared with the traditional extraction method using resonant frequency,this method is faster and more effective for the substrate integrated waveguide.A three-class SIW filter is successfully verified and designed by using this method,and a complete design process is given.2.In chapter 3,we explain the cross coupling theory of filter,and verify the theory with simulation software.Then,based on the resonator cross-coupling and end-coupling theories,a single-mode SIW filter with double transmission zeros is proposed,and its performance is compared with that of the cascade structure,which proves the effectiveness of the improved out-of-band suppression performance by quoting transmission zeros.On the other hand,after comparing the results,it is found that the method of introducing terminal coupling will introduce large radiation loss at high frequencies.Therefore,based on the first structure,a two-mode SIW filter is proposed through reasonable use of high order mode,which can achieve better frequency response with smaller circuit area and insertion loss.3.In chapter 4,we explain the high order mode suppression technique according to the field distribution of SIW resonator.On the basis of the filter structure proposed in Chapter 3,a half-mode and quarter-mode mixed coupled SIW filter with wide stopband response is designed by using high order mode suppression technology and cross coupling theory.The proposed filter has a stopband suppression frequency of up to 4.3F0 with the introduction of transmission zero to achieve fast rolldown speed,and the overall circuit area is reduced by more than half compared with the all-mode filter in Chapter 3.4.In Chapter 5,a frequency reconfigurable substrate integrated waveguide filter is designed based on the fluidity of liquid metal.Under the influence of gravity field,the switching between two frequency bands is realized by reversing the face up and face down placement of the filter.Then we design a multi-state air substrate integrated waveguide filter with screw adjustment,which can not only affect the single-mode resonator,but also make it switch between single-mode and dual-mode resonators.With the high Q value of the air cavity,the ultra-narrow band and low loss characteristics are achieved.