The Miniaturization Research Of Cavity Filter

Filter as a frequency selection device is an indispensable part of the system in the S-band microwave communication system.After a long time of high-speed development,the microwave communication frequency band has been very crowded,the index of the filter directly determines the overall performance of the communication system.As a kind of filter with low loss,high rectangular coefficient and the widest stop-band,cavity filter can improve the sensitivity,signal-to-noise ratio and anti-jamming ability of the receiver to the greatest extent,but it is also one of the filters with the largest volume.The miniaturization design technology of S-band cavity filter has made great progress after years of research,but it is far from the miniaturization demand of the system.The subject further discusses the method of filter miniaturization design by increasing the loading capacitance on the basis of electromagnetic theory,tuning theory and microwave resonator theory,combined with the classical theory of microwave filter design,which obviously reduces the volume of S-band cavity filter and promotes the research of cavity filter's miniaturization.The miniaturization design of cavity filter and two design methods of miniaturization cavity filter working in S band are proposed in this paper.One of them is a new type of resonator by adopting a new interdigital structure,setting a ring with a groove on the flange plate of the resonator rod,and setting a ring matching the resonator rod on the cover plate,and finally forming a new type of resonator;the other is using a new type of layered structure,setting a multi-layer layer on the flange plate of the resonator rod.The body and the cover plate are arranged at the side edge,and the cover plate is provided with a sheet body matching the resonant rod,thus forming a new type of resonator.The coupling structure is determined by the field distribution combined with the field simulation software HFSS,and the input-output coupling structure is optimized by the group delay method in the research and analysis process,.Then the optimal physical size of the filter is determined by the overall simulation and optimization of the filter.Through the research and test of S-band miniaturized cavity filter,it is shown that the volume of the cavity band-pass filter working in S-band is reduced by more than 26.5%.While reducing the sensitivity of debugging,it also has the effect of reducing temperature drift and improving the environmental adaptability of the miniaturized cavity filter.The research results of this project are applicable not only to S band,but also to other working frequency bands.With the improvement of machining technology,the two design methods proposed in this paper can further improve the miniaturization effect of cavity filters by adding interdigital structure or layers in the future.