Research On Compact Cavity Filter And Multiplexer

In the past few decades,cavity filters and multiplexers have played a very important role in mobile communication and satellite communication systems.The main reason is that the cavity structure has the advantages of low insertion loss,high unloaded Q value and superior power capacity.Currently,the deployment of the mobile communications is mature,and when a new generation network(such as 5G)needs to be installed,it needs to be added to the existing network(such as 3G and 4G).Based on this requirement,compact multi-band filter and tunable filter can effectively manage hardware resources,satisfy multi-system requirements,and achieve network capacity optimization.Aiming at the current research focus of compatibility with various communication resources,this paper studies and designs several cavity filters,including coaxial cavity dual-band filter,rectangular waveguide cavity triple-band filter,dielectric-filled waveguide filter and tunable coaxial filters,and extends the design to the diplexer/multiplexer.The main content of this paper is summarized as follows:1.Based on the resonant characteristics of the stub-loaded resonator,the structure of open-circuited and short-circuited stub-loaded coaxial resonator is analyzed in detail.Firstly,according to the resonant characteristics of the coaxial cavity stub-loaded resonators,the corresponding relationship between the resonant frequencies of the first two resonant modes and the physical structure is analyzed,and the frequency variation trend and variation range within that available physical structure is able to be realized are obtained.Then,according to the distribution characteristics of electric and magnetic fields of the resonant modes,relatively independent and controllable coupling structures are designed,including external coupling and internal coupling.Finally,the concept of common resonator is integrated to design the diplexer,which can reduce the total number of resonators and reduce the complexity of the structure.The research results have been published in IEEE Transactions on Microwave Theory and Techniques.2.Based on the ridge waveguide resonator,according to the cavity perturbation theory,the structure of this type of resonator is analyzed in detail.Firstly,according to the physical meaning of the cavity perturbation theory,the effect of the perturbation position on the resonant frequency is analyzed,the resonant characteristics of the quadridge waveguide resonator under the perturbation condition are theoretically deduced,and the frequency variation trend and range within the available physical structure are obtained.Secondly,according to the distribution characteristics of electric and magnetic fields of the resonant modes,relatively independent and controllable coupling structures are designed,including external coupling and internal coupling.Finally,the concept of common resonator is integrated to design the triplexer to reduce the total number of resonators and reduce the complexity of the structure.The research results have been published in IEEE Transactions on Microwave Theory and Techniques.3.Based on the coupling matrix synthesis theory of the microve filter design,the novel coupling schemes characteristics of transmission zeros shifting with frequency are studied.According to the dual-mode dual-ridge dielectric-filled resonator,the characteristics of transmission poles and transmission zeros of the building block are thoroughly analyzed.Based on the analyze above,two building blocks are cascaded by simple coupling iris,which provide filter model design.In this configuration,the designed filter can obtain quasi-elliptic response while still maintaining the inline structure.Another advantage of this configuration is that it extends the property of the traditional box section to that of the box-like section,which means that the complementary response and symmetric response can be both obtained by the same physical structure.4.Based on the inline dual-post resonator,a novel X-band tunable filter and tunable diplexer are studied.The most interesting feature of using inline dual-post resonator is that the input/output coupling and inter-resonator coupling are inversely proportional to the frequency within tuning range,which is necessary for maintaining fixed absolute bandwidth of the tunable filter.In addition,the novel waveguide H-plane Y-junction is proposed and cascaded with two tunable filters to realize the tunable diplexer.The research results have been published in IEEE Transactions on Microwave Theory and Techniques.