Research On Multilayer High Selectivity Bandpass Filter

With the rapid development of wireless communication systems,the demand for spectrum resources is becoming increasingly tight,and the requirements for the performance of microwave filters are getting higher and higher.In order to filter out the spectrum interference between adjacent channels,reduce the insertion loss,reduce the size of the filter and other design requirements,it is of great significance to design a miniaturized and high selective performance bandpass filter.This thesis explores the generation mechanism of ring dual-mode resonators,split ring resonators(SRR),interlayer coupling structures,cross-coupling structures,and defective ground structures(DGS)while aiming at the multilayer technology of microwave filters.These structures are used in the design of this subject,and a series of microwave filter circuits are finally designed.The main contents of this thesis are as follows:(1)The method to realize the miniaturization of the filter is introduced,the generation mechanism of the multi-layer coupling structure,the working principle and law of the dual mode of the resonator are analyzed,and the equivalent circuit is constructed by the odd and even mode analysis method,and the detailed analysis is carried out.(2)The method to improve the selectivity of the filter is introduced,and the working mechanism of the resonator cascade structure that can improve out-of-band suppression,the defective ground structure(DGS)with band rejection characteristics,and the cross-coupling structure that can generate transmission zeros are analyzed.In addition,the advantages and disadvantages of the resonator cascade structure are compared and analyzed.(3)Based on the research to improve the overall performance of the filter,a dual-mode band-pass filter based on the circular ring microstrip structure is designed.This design meets the requirements of miniaturization of the filter and has high selectivity,and is simulated by HFSS software.Analysis,physical processing and testing have verified the rationality of the design method;a high-selectivity band-pass filter based on SIR structure is designed,the design structure is simple and novel,and the in-band performance and frequency selectivity of the filter are good.(4)Finally,based on the bandwidth tunability of the stepped impedance resonator(SIR)and the double-pole band-rejection characteristics of the defective ground structure(DGS),a combination of high-selectivity multilayer bandpass filters was designed,and Based on the design,the method of comparative research was used to analyze the influence of different microstrip lines and slot structures on the performance of microwave filters;based on the characteristics of two sets of non-adjacent resonator cross-coupling structures between layers that can produce transmission zeros,the design A multi-layer band-pass filter with high selectivity;based on the cross-coupling structure,it can produce the transmission zero characteristic and the double-pole band rejection characteristic of the defect ground structure(DGS),and a combination of high-selectivity multi-layer Three pass band pass filter.