Study On Bandpass Filter Based On Spoof Surface Plasmon Polaritons

Spoof Surface Plasmon Polaritons(SSPPs)are developed on the basis of Surface Plasmon Polaritons(SPPs).It is a kind of surface electromagnetic wave produced by etching periodic structure on metal surface.It propagates along the surface of the metal and medium and decays exponentially in the direction perpendicular to the metal surface.SSPPs are widely used in RF device design because of their characteristics of high binding,low loss and high transmission efficiency.In this thesis,the characteristics of SSPPs unit are analyzed,and the related theories of short-circuit stubs structure,interfinger coupling structure and substrate integrated waveguide are studied and designed.The main research contents are as follows:(1)An ultra-wideband bandpass filter based on SSPPs is proposed.Firstly,a new SSPPs unit structure is designed,which has higher adjustability than the traditional structure.On this basis,a low pass filter is designed,and the low pass filter and shortcircuit stubs are cascaded to realize an ultra wideband bandpass filter.The band-pass filter has the characteristics of high and low cutoff frequency independent adjustable and simple structure.The final test results show that this filter has good bandpass characteristics in the range of 3GHz-13 GHz,the bandwidth is 125%,the in-band insertion loss is less than-2.5d B,the return loss is better than-13.5d B.The out-of-band inhibition reaches-25 d B at 2.1GHz and 13.7GHz,respectively.(2)A SSPPs bandpass filter with hybrid interdigital coupling ctructure is proposed.The filter etched interdigital coupling structure on the SSPPs unit to achieve bandpass characteristics,with high and low cutoff frequency independent adjustable and miniaturized characteristics.Compared with the reference,the effective size of the filter is reduced by 16%.At the same time,the transmission efficiency of the filter is improved effectively by adjusting the structural parameters of the SSPPs-interdigital coupling unit in a graded way.The final result shows that the-3 d B passband range of the filter is 9.64 GHz to 13.32 GHz,and the bandwidth reaches 32.06%.The in-band insertion loss is less than-3 d B,the return loss is better than-13.5 d B,and the out-ofband suppression reaches-20 d B at 8.9 GHz and 14.1 GHz,respectively.(3)A SSPPs bandpass filter with hybrid half-mode substrate integrated waveguide is proposed.The filter etches SSPPs structure on the surface of HMSIW with high-pass characteristics to realize bandpass characteristic,and has the characteristic of high transmission efficiency.The final simulation results show that the filter has good performance in the 6.5GHz-10.1GHz passband,and the bandwidth reaches 43.4%.The in-band insertion loss is less than-3 d B,the return loss is better than-15.1 d B,and the out-of-band suppression reaches-30 d B at 5.8 GHz and 10.4 GHz,respectively.