| Microwave filter is one of the indispensable equipment in modern wireless communication system,which plays an important role of frequency selection.Among them,the cavity filter has been widely used in various kinds of communication equipment because of its high Q value,low insertion loss,high power capacity and so on.Due to the influence of the thermal expansion coefficient of the material,the structure of cavity filter will deform when the temperature changes,which affects the frequency response.Therefore,it is necessary to study that how to guarantee the cavity filter to work properly and reduce or even eliminate the frequency response of temperature drift phenomenon in a certain temperature range.In this paper,the temperature compensation of cavity filter is studied based on the multi-physics coupling analysis.The temperature compensation of microwave filter has been studied for several decades,and various kinds of temperature compensation methods and structures have been proposed.The past design methods of temperature compensation structure were derived mainly on the basis of approximate processing method of empirical data and the large number of repeated experiments,and its design efficiency was low.In order to accurately analyze the actual working state of the microwave filter and efficiently design the temperature compensation structure,a multi-physics coupling method of microwave cavity filter is proposed to realize the efficiently design of temperature compensation structure.The main contents of this paper are as follows:Firstly,the synthesis theory of microwave filter is briefly introduced.The calculation of coupling coefficient and external quality factorQ_e are introduced in detail.It has analyzed the influence of temperature drift on the microwave filter and deduced the mathematical relationship between the frequency response and the amount of change in temperature.Furthermore,the multi-physics field coupling relation and the solution strategy and method are summarized,and the multi-physics coupling collaborative analysis simulation method is proposed for microwave cavity filters.It has given the mixed heterogeneous model of microwave filter and the multi-field coupling analysis process.Secondly,this paper introduces the design process of coaxial cavity filter based on space mapping method.At the same time,it briefly introduces the basic principle of space mapping and designs a 4-order coaxial cavity filter in this way.On this basis,the temperature compensation is carried out by the method of multi-physics coupling collaborative simulation analysis,and the temperature compensation structure is designed accordingly.In the temperature range of-40?to 100?,the frequency response caused by the temperature drift is reduced and the high thermal stability is achieved.Finally,a Ku band waveguide filter is designed in this paper.The multi-physics coupling collaborative analysis of the filter is carried out,and the temperature compensation structure of loading thermal bimetal strips is designed.In the-20?to 100?temperature range,the waveguide filter can still maintain the target response and good thermal stability. |
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