Research And Implementation Of Miniaturization Of Multi-evanescent Modes For Microwave Filters

The miniaturization and integration of the system has become the current research hotspot with the rapid development of radar,communication system and navigation technology.As an irreplaceable component of communication systems,microwave filters play an important role in suppressing channel interference and reducing signal noise.Because of microwave devices such as filters and duplexers affect the volume and weight of wireless system,it has become an important research content which realize the miniaturization of filters and duplexers under the premise of achieving performance.Multimode technology and evanescent mode technology are both conventional methods to realize miniaturization of filters,duplexers and other devices.Multimode technology and evanescent mode technology are always applied to miniaturization research independently in the current research efforts at home and abroad,In order to further realize the miniaturization of passive components,this paper discusses the combined application of multimode and evanescent mode in coaxial cavity.The main contents and achievements of this paper are as follows.1.It analyzes and studies the field distribution of coaxial transmission line,the novel multievanescent mode resonator structure is presented by analyzing the characteristics of mode,mode and mode distribution of coaxial waveguide.According to the theory of wave impedance and resonator of coaxial transmission line,the paper discusses the effects of resonant frequency,unloaded quality factor and configuration of resonator and the tuning method of resonant frequency and the technical means of improving quality factor,a multimode excitation method of metal through holes loaded by a coplanar waveguide(CPW)feeder at the bottom of the resonator has been realized.Finally,combine with the substrate integrated waveguide technology(SIW),a band-pass filter with a center frequency of 4GHz is designed by using the multi-vanished-mode resonator,and it is processed,assembled,tested and verified.2.It studies a novel structure of diplexer by studying the application of multi evanescent mode technology in the design of diplexer.Based on the research of multi-evanescent mode resonator,by analyzing the input impedance of the filter and combining with the dual frequency impedance transformation theory,the impedance matching problem of diplexer common port which the traditional T-type joint has been solved.Analyzes and studies the main parameters affecting the transmission and isolation performance of the diplexer,combines with the electromagnetic simulation software,the design of high-performance and miniaturized duplexer with working frequency of 2.4GHz and 4GHz is realized,and the machining and testing are carried out.3.It presents a novel structure of dual frequency filter based on multi-evanescent mode technology by studying the application of multi-evanescent mode technology in the design of dual frequency filter.The paper studies and designs the dual frequency matching network of the port,analyzes the main parameters of port matching transmission line which affect the transmission characteristics of dual frequency filter.By optimizing the parameters of electromagnetic simulation software,realizes a dual frequency filter with new structure which working frequency is designed at 2.4GHz and 4GHz.