Research On Palanar Microwave Filters Based On Spoof Sureface Plasmon Polaritons

Based on the Spoof Surface Plasmon Polariton(SSPP),four kinds of novel planar SSPP microwave filters are proposed in this thesis,where structures and theories of these novel filters are introduced in detail.Dispersions of the proposed filters are also investigated.The filters are also simulated and measured to vertify the theories.This thesis contains the following results:Firstly,a low insertion loss low-pass filter(LPF)based on the SSPP is proposed in this thesis.By optimizing the regular structure parameters of the single comb-shaped SSPP LPF,the low insertion loss filter with unregular structure parameters is achieved.The optimization processing improves the reflection cofficient and insertion loss at the near-zero-hertz band and the out-of-band rejection of the filter,where the filter size is also reduced.The dispersion comparison result reveals the reasons behind the improved performances.The better performances of the optimized filter proves that breaking the regularity of traditional SSPP filters is beneficial to the filter's performances.Secondly,the novel planar hybrid SSPP-SIW filter with wide passband is proposed.The filter embeds the planar double-grating SSPP into the metal area between two columns vias of the SIW,where transmission modes and frequency characteristics of the SSPP and the SIW are combined and a wide passband filter with controllable sidebands is consequently achieved.The transmission efficiency is alleviated and the insertion loss also keeps a low value in the hybrid filter.Besides,the out-of-band rejection is also improved from traditional filters.Thirdly,a novel single-band SSPP rejection filter is proposed.The filter inserts folded split-rings into gaps of the low-pass SSPP filter,where the frequency characteristics of pass-reject-pass is consequently achieved,and size of the low pass filter is not increased.The filter structure is simplified from conventional filters and the rejection bandwidth also can be controlled by the geometric parameters.The dispersion frequency characteristics of the SSPP unit are invesigated and it is proved to be consistent with the S parameters of the filter.The approaches of controlling the S parameter by the structural parameters are also presented.Finally,two novel dual-and tri-band SSPP rejection filters are also implemented by cascading the single-band SSPP rejection units with diverse rejection bands,thus the rejection bands in each filter are mutually independent.Compared with similar multi-band SSPP rejection filters,the proposed ones provide more compact filter sizes,wider rejection bands,and better frequency characteristics controllability.And the control on the rejection bands is also achieved.Compared with non-SSPP multi-band rejection filters,the proposed SSPP filters provides deeper rejection depths and steeper rejection sidebands.The similarities and differences between cascaded non-periodical SSPP with multiple rejection bands and periodical ones with single rejection band are also presented,and the control approaches on the S parameters are also introduced.The fabricated filters are also measured to prove the design approach.