Design And Implementation Of Tunable Cavity Filter

With the rapid development of modern communication,microwave filters are widely used.Frequency tunable band-pass filter is a new type of microwave filter.Its band-pass frequency can be changed with the change of working frequency.The tunable coaxial cavity filter not only has many advantages,such as high power,tunable,narrow bandwidth and so on,but also has a high Q value.It is mainly used in microwave receiver and electronic countermeasure system.It can not only achieve frequency anti-jamming,but also meet the best matching filter criterion.It is an important technical means to solve the same address interference of the system,and plays an important role in the anti-jamming technology of communication system.Through the theoretical research of microwave cavity filter,combined with the use of Ansoft HFSS computer simulation software,the design of mechanical tunable coaxial cavity filter includes: the design of overall scheme,the design and implementation of filter,the design and implementation of microwave tuning structure,the design and implementation of control circuit,the design and Implementation of interface programmable control software,etc.The frequency of tunable cavity filter is continuously tunable in a wide range.And the control software can store the position of the resonance bar when the filter is at different center frequency.When using,only the required frequency is input,and the control software can automatically control the resonance bar of the filter to adjust to the corresponding position.In this thesis,the tunable cavity filter designed by the research has been processed in kind,and has been debugged repeatedly.Its actual test performance index is good,which meets the technical index requirements of the project,realizes the tunable function of the filter frequency.And it gets a good application in the actual project.The design of tunable cavity harmonic filter needs to solve the problems of coupling physical mechanism,tuning mechanical mechanism,motion control software and so on.The following aspects of this thesis play a key role in the design and implementation of the filter:(1)The design scheme of the high Q-value tunable filter and the coupling mechanism between cavities is proposed.The Q-value of the resonator is increased from 1500 to 5500 by the combination of the coaxial cavity and the tuned moving component,which significantly reduces the loss of the filter;(2)Through the design of high-precision filter moving component and the control technology of moving zero point,the problem of high-precision control under the large stroke is solved,and the requirements of moving stroke of tuning rod 12.5μm and tuning accuracy of 25 kHz are realized;(3)This thesis puts forward the stamping bump design technology of the grounding spring,and adopts the flexible anti assembly technology of the grounding spring and the hard silver plating technology of the tuning rod to solve the power resistance problem of the filter,improve the reliability and stability,and meet the needs of the environment.