Study On Novel Single-band And Multi-band Filters Based On Substrate Integrated Waveguide

The rapid development of modern automotive radar,high-definition video,and satellite communications systems has caused the exhaustion of existing frequency resources.As a result,higher-performance,smaller-size,and multi-bands are required for the design of frequency-selective devices,which are microwave filters.Substrate Integrated Waveguide(SIW),as a new type of waveguide structure,has emerged in the past decade.Because of its advantages of combining metal waveguide and planar microwave transmission line,it is widely used in microwave filters design.However,how to SIW and how to apply the technology in the design of multi-frequency filters are still difficulties.Therefore,based on a thorough investigation of SIW filter miniaturization and SIW multi-frequency filter researches,some new methods about desigining novel single-frequency and multi-frequency SIW band-pass filters have been developed in this thesis.Firstly,based on a traditional one-eighth-mode SIW resonant cavity,this thesis presents a novel one-eighth-mode resonant cavity with etching fractal defects.Based on this,a fourth-order band-pass filter was designed to reduce its size by 90%.At the same time,two transmission zeros(TZs)were produced by introducing cross coupling and slot compensation coupling in the design,which greatly improves the out-of-band rejection performance of the filter.Secondly,based on an equilateral triangle SIW resonator,the concept of one-third-module SIW is first proposed in this thesis whose size reduced by 75%.Then a single-frequency and dual-frequency filters are designed based on it.The single-frequency filter not only has a simple structure and a compact size,but also has a wide stop-band due to a TZ which generated by adjusting the relative position of the feeds.Meanwhile,the dual-band filter is designed by using high-order mode technology.It possesses all the advantages of the single-frequency filter,and also generates a TZ due to the introduction of the complementary split ring resonator(CSRR)structure,which improves the frequency selection of the filter.Thirdly,a 90° SIW resonator was proposed and analyzed firstly in this thesis.Based on this,a dual-band tunable band-pass filter was designed using high-order mode technology.On the one hand,the first pass-band is independently adjustable by introducing the metal perturbation in the 45° direction;on the other hand,the CSRR is excited by the higher order mode for the first time,which achieves the second pass-band independently adjusting.Based on the above,a dual-band tunable band-pass filter was designed and five TZs are generated by introducing source-load-coupling which greatly improves its out-of-band performance.Finally,based on the equilateral triangle SIW resonator,a completely new method of perturbation by metal vias is proposed.Compared with previous papers,this method can perturb two modes which in one cavity,meantime,for a third-order filter,the perturbation is only loactaed in the middle cavity.Based on this method,a tri-band bandpass filter is designed.By introducing the source and load direct coupling structure and CSRR,the filter can generate 8 TZs out of band,which makes it have excellent out-of-band performance.It provides new ideas for the design of tri-band and above SIW filters.