Research On Compact Tri-Band Microwave Filters Based On Novel Resonators

With the rapid development of wireless communication technology,multi-band filters that can be used in different communication levels have become the focus of radio frequency circuit research for years.Based on the novel T-shaped dual-mode,quad-mode and eight-mode resonators,this paper studies the miniaturization and high-performance compact tri-band bandpass filter.First,the research progress of microwave filters in recent years is introduced;the basic theories of RF microwave filters are studied,including the background,skills and applications of the odd-even mode analysis method,and the resonance characteristics and requirements of the four types of applications are analyzed in detail;The comprehensive basic theory of the device has been explained in detail,laying a solid theoretical basis for the subsequent practical research and related technologies.Then,a novel low-loss and ultra-compact tri-band filter with controllable passband was designed for UHF applications,such as GSM,RFID special,Aviation Satellite Navigation and China Mobile TDD,etal.The filter is composed of three T-shaped ?/4 dual-mode resonators.Changing the length of three relatively independent resonant paths in the resonators helps to control each passband independently,according to the desired stopband frequency on both sides of the passbands to control the transmission zeros.A miniature tri-band bandpass filter was designed and produced.The simulation results show that the center frequencies of the three passbands are 0.84,1.59,and 2.63 GHz,the insertion loss is 0.07,0.23,0.43 d B,and the-3 d B relative bandwidth is 63.1 %(0.45?0.98 GHz),16.4%(1.48?1.74 GHz),6.8%(2.55?2.73GHz),the return losses are better than 20 d B.The physical circuit test basically accords with the simulation result.Then,a novel tri-band filter based on the combination of a stub-loaded quad-mode resonator and a T-shaped dual-mode resonator is proposed.The stub-loaded quad-mode resonator forms the first and third passband,and the T-shaped dual-mode resonator forms the second passband,so three passbands can be independently designed.In addition,two transmission zeros are created to enhance the isolation between two adjacent passbands,and a good tri-band filtering response is obtained.Subsequently,a novel compact tri-band filter with a wider third passband was proposed to meet the requirements of 5G wireless network applications.The filter uses a novel multimode resonator with eight resonance modes.Using these modes,a tri-band filter with controllable operating frequencies is designed.Among these three frequency bands,the high frequency band is realized by four modes covering the 5G Wi Fi frequency band.The other two passbands with 2.4GHz and 3.3GHz as the center frequency are realized by the other four modes respectively.In order to verify the proposed idea,a tri-band filter was designed.The simulation results show that the center frequencies of the three passbands are 2.4,3.3,and 5.4 GHz,and the insertion loss is 0.63,1.11,0.88 d B,and the-3 d B relative bandwidth is 15.4%,5.9% and 19.4%,covering WLAN,Zig Bee,Wi Fi,Wi MAX and 5G Wi Fi systems,and the return loss is 31.4,33.1,13.8 d B.The simulation results are basically consistent with the theoretical analysis.Finally,it summarizes the experimental research work of the full text,analyzes the deficiencies that need to be improved in this article,and proposes prospects for the follow-up research work in view of the problems in the field of radio frequency and microwave.