Researches On Microwave Filter Diagnosis Techniques And Applications

With the development of wireless communication technology,microwave filter as an important part of RF front-end system,technical requirements getting higher and higher,and the market demand is growing.Microwave filter design optimization and tuning often cost a lot of manpower and resources,in order to save time and reduce costs,It is necessary to improve the filter design and tuning efficiency.Filter diagnosis technology is which in the filter design and tuning process,according to the simulation or test response data,using the derived calculation method to determine the resonant frequency and the coupling element value of the filter,and compare with the theoretical target value,which can guide the optimization and tuning.It can greatly facilitate the design and tuning of the filter,improve the efficiency,save time and reduce costs,it has important engineering value and application prospect.This thesis focuses on the diagnosis and tuning of microwave narrow bandpass filter and its related applications.Then programming diagnosis algorithm based on Matlab,and studies the practical simulation design and tuning of two filters based on the diagnosis technology.In addition,this thesis also carries on the simulation research to the filter of the high Q resonator based on the loading negative resistance.The contents of this thesis are as follows:1.The basic theory and performance of microwave filter network are introduced.The correlative formulas are given,and several main filter diagnosis techniques and their tuning steps are described in detail.2.Based on the diagnosis technique of the admittance parameter extraction,the coupling matrix corresponding to the filter measurement data is synthesized.First,the phase loading effect of the measured data is removed,then the pole and residue of the admittance parameters are extracted by the vector fitting method.Then the N+2 transverse coupling matrix is synthesized.Finally,the coupling matrix corresponding to the filter topology is optimized.The method can be applied to the auxiliary design of microwave narrow bandpass filter or the diagnosis and tuning.It can obtain the adjustment direction and amplitude quickly and accurately,reduce the design time and shorten the project cycle.3.The eighth-order microstrip open-loop resonator bandpass filter is designed and simulated with the diagnostic technique of the last chapter.The simulation iteration number is 29 times.The simulation result is consistent with the target curve.The fourth-order dielectric cavity bandpass filter is simulated and tuning,it costs 13 times of adjustment to achieve the requirement,which takes 2 hours.The simulation curve is in good agreement with the ideal curve,and the tuning procedure is given.The unloaded Q value of the resonator is extracted,which proves the feasibility of the diagnosis technique.4.The negative resistance concept is discussed and a floating-type negative impedance converter circuit is designed and then applied to the second-order microstrip bandpass filter and the LC bandpass filter respectively,which greatly improves the resonant unload Q value to reduce the insertion loss of the filter.This type of negative resistance compensation filter has the advantages of small size and easy integration.