Research On Dual-mode Microstrip Bandpass Filter

With the rapid development of science and technology,the degree of integration and refinement of devices has become higher and higher.With the ever-increasing performance requirements for transceivers,the performance,size and cost of filters have become increasingly demanding.The microwave filter is an important part of the microwave/radio frequency system.Increasing the filter performance and cost has become a hot and difficult issue for researchers.This paper mainly studies the design method of the dual-mode band-pass filter,and uses the electromagnetic simulation software(HFSS)to carry on the simulation optimization to the designed filter,has obtained the good result.First,after deeply analyzing the relevant resonant characteristics of the microstrip patch resonator,a new type of resonator is designed based on the basic square patch resonator structure.Through the introduction of square cut-off corner perturbation to achieve the separation of degeneracy mode,and input/output orthogonal direct feed mode,reduce radiation loss.In this way,a dual-mode band-pass filter with source and load directly coupled is designed.The filter designed in this way has a high stop-band rejection performance and meets the requirements for miniaturization and high performance of the filter.Secondly,based on the square patch filter designed above,a dual-mode dual-passband filter was designed using the mirror cascade method.The resonator of this structure can increase the bandwidth and adjust the center frequency during the design of the filter.And can make the filter have the advantages of high pass band selectivity and high out-of band suppression.Finally,based on the quarter-impedance resonator,the basic resonant unit is formed by loading the branch line at the center,and the dual-mode pass band filter design is completed by this method.And use the odd-even mode analysis principle to analyze the structure of the resonator.The filter designed with this structure generatestransmission zeros on both sides of the passband,which can effectively suppress the spurious frequency and improve the frequency selection performance.The simulated data of the microstrip dual-mode filter designed in this paper is compared with the measured data.The obtained simulation diagram is basically the same as the measured one,which verifies the reliability of the design of this paper.