Research And Design Of Multiband Bandpass Filter Based On New Multimode Resonator

Multi band and miniaturization of wireless communication systems is one of the trends in the development of modern communication systems.Due to the nonrenewable spectrum resources and the coexistence of multiple communication methods,single band narrowband communication systems are increasingly difficult to meet the requirements of modern communication.Due to its simple structure,easy processing,low cost,and easy implementation of miniaturized,multi band bandpass filters using multimode resonators have become a hot topic in the research of modern communication systems.This paper proposes a series of multi pass band filter structures using multimode resonators flexibly,combined with notch units and defected ground structures to improve the overall performance of the filter.The main research contents of this topic include:1.This paper describes the research background and significance of multi band pass filters,as well as the current research situation at home and abroad.After that,it lists and illustrates the relevant theoretical basis for filter design.2.A dual-band bandpass filter with multiple transmission zeros is proposed.The filter adopts a four-mode resonator based on center-loaded short stub to provide two passbands;Three pairs of rectangular defected ground structures with different sizes were introduced to improve the return loss performance of the filter;A step impedance notch unit and three pairs of uniform impedance notch units were coupled to the filter,and a pair of asymmetric interdigital input/output feed lines with source-load coupling structure is designed.Multiple notch units and feed lines with source-load coupling structure generate six transmission zeros,improving the passband isolation and high-frequency out of band suppression performance of the filter.3.Two dual-band bandpass filters with different input and output structures are designed.They use the same resonator structure,but one filter uses a parallel coupled feed and the other uses a coplanar waveguide feed.The simulation and test results of the two filters are compared,and the impact of different feed structures on the filter performance is analyzed.4.Two four pass band filters with double resonator structure are designed,which are based on the above two pass band filters.The first filter uses the tri-mode resonator with a center loaded open stub,and the second filter uses a double open stub loaded resonator.The two filters were simulated,fabricated,and tested.