The Study Of Multi-mode Wideband Cavity Bandpass Filters

With the rapid development of communication in recent years,higher demand on performance of communication system.Filter,as the key components of the telecommunication system,have a huge impact on quality of communication.Cavity filters are widely used in communication base-station and digital video broadcasting with the characteristics of high power capacity,low loss and high quality.Nowadays,it is as hot topic for broadband,miniaturization,higher-isolation and low-loss,with the commercial used of 4G technology and further study on 5G technology.Our primary objective of this work is to explore a miniaturized and wideband cavity filter,and study for excitation of resonant modes and coupling between them.Finally,a multi-modes wideband filter will be realized.The main contribution of the dissertation can be summarized as follows:(I)Without any tuning screw elements and corner-cuts,utilizing one or more perturbation metal cylinders excite multiple resonant modes(both TM modes and TE modes)in single cavity,and controlling the coupling between them.Finally,it is realized several filters have characteristic with multi-modes and broadband.What is more,the fractional bandwidth is up to 30%.(II)Based on simplicity of structure,only one type resonant mode can be excited in one waveguide cavity,namely,TM modes.What is more,three resonant modes exciting in this cavity are utilized to form a triple-mode wideband filter with the fractional bandwidth of 58%.(III)It is found that utilize an off-centered triple-modes dielectric resonator(DR)instead of a traditional corner-cuts perturbation to design a triple-mode dielectric filter.It is an effective method with easy design and processing difficulty.(IV)On the base of the above study,some potential further research directions are analyzed to expand the study and enrich the applications of passive components,such as filters and diplexers.