Design And Research Of Cross-coupled Dielectric Waveguide Filter For 5G Applications

This thesis mainly studies dielectric waveguide filter based on cross coupling technique.Dielectric waveguide filter has gradually become a research field of concern.The filter has small physical size,uses high dielectric constant material and has high Q value characteristics.In recent decades,with the rapid development of wireless communication technology,available spectrum resources are more and more limited.In addition,it is necessary to avoid interference between adjacent channels and improve the communication capability.Therefore,it requires high filter selection characteristics,good out-of-band suppression effect,and low loss,miniaturization,easy integration,light weight and so on.Metal cavity filters used to be widely used in base station RF systems,but the new requirements of 5G require the development of filters towards the direction of miniaturization,low cost and easy integration,and traditional filters are difficult to meet these requirements.With the continuous study of ceramic dielectric waveguide filter,it can not only take into account the design requirements of miniaturization,lightweight,easy integration,but also because of its high selectivity,gradually become a new choice of The Times.In this paper,the crosscoupled structure,new resonator structure,dielectric waveguide,filter,dual-mode filter are studied,and several dielectric waveguide filters are realized: the cross-coupled filter of rectangular waveguide resonator,the dielectric waveguide filter of new triangular resonator,and the dual-mode dielectric waveguide filter.The designed filter has the advantages of strong out-of-band suppression,good inband performance,small volume,small insertion loss,good temperature stability,high performance(especially stopband)narrow-band filtering,through hole installation,strong vibration resistance,suitable for high reliability applications and 5G communication.It provides application value for the development of filter.The main innovation points and main work of this thesis are summarized as follows:1.A 6-order dielectric waveguide filter with rectangular resonator structure is proposed.On the basis of the proposed positive coupling structure and negative coupling structure,a cross coupling dielectric waveguide filter is designed.The positive coupling is achieved by grinding the blind hole and coupling wall on the rectangular resonator,and the negative coupling is achieved by grinding the deep blind hole.A single sideband suppression band-pass filter is realized.The parasitic response is suppressed by adjusting the center frequency of the filter by grinding a metallized cylindrical throughhole in the middle of the resonator.Finally,the designed filter is simulated and tested.After testing,the center frequency of the filter is about 3.505 GHz,the actual working bandwidth is 230 MHz,the relative bandwidth is 6.56%,the insertion loss is less than 0.3d B,the return loss in the passband is greater than 16 d B,and the out-of-band suppression effect is good,up to-60 d B.2.A based on novel isosceles right triangle resonator cross coupling technique filter is proposed.Based on the isosceles right triangle waveguide theory,an isosceles right triangle resonator structure is proposed,and the positive coupling design,negative coupling design and input/output design of the new structure are carried out.A four-order cross-coupled filter and an eight-order cross-coupled filter are designed and processed.Among them,the center frequency of the eighth-order filter is about3.5GHz,and the relative bandwidth is 5.71%.Compared to the fourth order filter,it has a good outof-band suppression effect,and the out-of-band suppression is below-70 d B.The new structure of the resonant cavity changes the original rectangular structure,can effectively reduce the size of the filter,has low insertion loss and superior out of band suppression effect.3.A two-mode dielectric waveguide filter is designed.A new two-mode design theory is proposed,including the design of two-mode resonator,the design of coupling structure between resonators and the design of input/output coupling.A four orders double cavity double-mode filter is proposed based on double-mode theory.In a two-mode resonator,two different TEM modes are produced by setting two vertical metalized blind holes in dielectric waveguide resonator.This structure design enables the filter to be miniaturized while maintaining good out of band inhibition characteristics.The coupling of the two modes in such a resonator can be effectively controlled by one or more metallized coupling blind holes.