Study On Computer Aided Tuning Of Cavity Filter

In recent years,the rapid development of broadband communication systems,the third-generation,the fourth-generation and the fifth-generation mobile communication systems and ultra-wideband systems,which are about to be put into business,proposes more stringent target to the new type of microwave devices.At the same time,satellite communication develops remote communication into many application fields such as mobile communication,aeronautical navigation,remote sensing and so on.Microwave resonators,such as microwave filters,duplexers,multiplexers and so on,are the key devices in the above systems.With the increasing tension and crowding in the communication band,the selectively target of filters become more and more prominent.Microwave circuit tuning is a complex work,which requires rich practical experience.The cavity filter is an important component of the microwave circuit.With the increasing of the filter order,the number of the parameters involved in the tuning is added,and the difficulty of tuning is also greatly increased.Multitudinous production of cavity filters is bound to invite many experienced workers,which will increase the cost of products.Therefore,improving the tuning speed of the cavity filter can be improved by computer aided tuning system greatly improve the efficiency of multitudinous production and save manpower cost.In this thesis,after analyzing the current research status of microwave filter aided tuning,a computer aided tuning system for cross coupled cavity filter is designed which is based on the Cauchy method.After comparing the various algorithms of the microwave filter parameters extraction,the Cauchy method is selected as the algorithm for extracting the coupling matrix of the filter,and the pre-treated technology of Cauchy method is proposed for solving the disadvantages of the traditional Cauchy method.The pre-treated technology of Cauchy method solves the problem of the accuracy of the parameters extraction using traditional Cauchy method which is influenced by the filters' unloaded Q value,what's more,it can accurately extract the characteristic polynomial coefficients of the filter and get the unloaded Q value of the filter at the same time.By introducing the genetic algorithm,a rotating elimination algorithm for the coupling matrix of arbitrary topology is designed,which can quickly transform the coupling matrix obtained by the modified Cauchy method to the one corresponding to the topology of the pending filter.On the MATLAB GUI platform,a computer aided tuning system of cross coupling filter based on the modified Cauchy method is designed,and the availability of this system is verified by the actual tuning case.In order to further verify the function and efficiency of the computer aided tuning system,a full wave simulation model of a six-order coaxial cross coupling cavity filter is designed and tuned.By using the computer aided tuning system,the response curve can be quickly tuned to fulfill the requirement.