Research On Notch Filter Based On Spoof Surface Plasmonic Polaritons

In recent years,spoof surface plasmonic polaritons(SSPP)have gradually attracted researchers' attention.By using a structured surface on the metal-dielectric surface,the SPP mode can be mimicked in a lower frequency range,such as microwave and radio frequency range,this mode is called SSPP.Based on the principle of SSPP,three microwave notch filters are proposed and designed in this thesis.Firstly,the structure and theoretical basis of these filters are introduced,and then the filter design is completed based on the simulation and analysis of their dispersion characteristics.Finally,the correctness of the design is verified by fabrication and measurement.The specific research contents are listed as the following three parts:Firstly,an SSPP filter with wide rejection is proposed.The stopband is introduced into the passband by loading two resonators,and the resonators are excited by back coupling,which cuts down the transverse size of the filter.The measured results show that the passband of the notch filter is stable,and the minimum insertion loss is 0.56 d B.The cut-off frequency of the filter is 7.86 GHz,the wideband notch frequency range is3.77 ? 4.51 GHz,and the deepest suppression in the notch reaches-21 d B.The measured results agree with the simulated ones well.Secondly,based on the design basis of fixed SSPP filter,a broad rejection filter with reconfigurable center frequency is designed by using the influence characteristics of SSPP periodic unit length on the asymptotic frequency of dispersion curve.Through the simulation of the dispersion curve of the periodic element,the reasonableness of the rejection realization principle is verified.The results show that the cut-off frequency of the filter is 14.43 GHz,the IL in the first passband is kept within 1d B,and the minimum IL in the second passband is 1.53 d B.The center frequency of notch can be tuned in the range of 6.68 GHz ? 8.49 GHz,and the bandwidths stay at 2.73 GHz still basically.The maximum attenuation within the notch range is maintained above 40 d B,and the deepest suppression can reach 55.6d B,which has a wide frequency tuning range and a good signal suppression effect.Finally,based on the hybrid structure,the substrate integrated waveguide(SIW)is combined with SSPP structure,and the bandpass response is constructed by combining the high-pass characteristics of SIW structure and the low-pass characteristics of SSPP structure.On this basis,due to the structural limitation of SIW,two notches in the passband are realized by introducing another layer of substrate and two pairs of openloop resonators loaded on its surface.The measurement results show that the passband range of the filter is 8.5GHz ? 11.8GHz,the two notch frequencies are located at10.56 GHz and 11.26 GHz respectively,and the notch depths are-16.92 d B and-21.64 d B respectively.The measurement is consistent with the simulation results,which puts forward a new idea for the design of notch filters based on SIW-SSPP hybrid structure.