Application Of High Order Modes In Substrate Integrated Waveguide Filters

Substrate Integrated Waveguide?SIW?filter has been widely used in practical engineering in recent years because of its high quality factor,small loss,small size,and easy integration.With the increasing requirement for the performance of the filter in the communication system,high-order mode is no longer the resonant mode required to suppress.More and more researches have shown that,high-order can be introduced not only to design for dual-band filter and dual-mode filter based on multi-mode resonator,but also construct cross-coupling to achieve quasi-elliptic filter,improving the stopband rejection characteristics.Therefore,this paper focuses on the application of high-order mode in the SIW filter.Based on the investigation of the current situation of ?-band SIW filter and combined with the project requirements,several ?-band SIW quasi-elliptic filters,?-band SIW dual-band filter and ?-band SIW dual-mode filter are designed.Firstly,based on the methods of physical cross-coupling and mode cross-coupling,the application of higher order modes in SIW quasi-elliptic filters are discussed in this paper.Moreover,the generation mechanism of finite transmission zeros is deeply analyzed and four SIW quasi elliptic filters are designed.On the one hand,cross coupling can be realized in single layer structure by introducing high-order mode,simplifying the grooving process and reducing the difficulty of processing.On the other hand,the generation of finite transmission zeros greatly improves the stopband rejection characteristics and the rectangular coefficients.Several filters have been successfully applied in practical projects.In addition,SIW dual-band filter and dual-mode filter are designed by using high-order mode.The SIW dual-band filter uses TE₁₀₁ and TE₂₀₁ mode,and its structure is simple,small size and easy to process.Different from the classical structure using TE₂₀₁ and TE₁₀₂ mode,this paper attempts to use the TE301 and TE₁₀₂ mode in the SIW dual-mode filter,so that the filter is symmetrical structure,which reduces the design difficulty.The experimental results show that the SIW filter designed in this paper is in good agreement with the simulation results,and has great engineering application value.