Research On Manipulating The Propagations Of Spoof Surface Plasmon Polaritons Based On Microwave Planar Transmission Lines

Spoof surface plasmon polaritons(SSPPs)are surface electromagnetic(EM)modes with surface plasmon polariton(SPP)-like properties.This dissertation's task is to explore the research of mechanisms of SSPPs and their propagating characteristics at microwave and terahertz frequencies.The applications of SSPPs with exotic features at microwave frequencies will certainly have revolutionary effects on improving the performance of traditional microwave devices.However,there are still many limitations of practical applications of SSPPs in traditional microwave planar circuits which need to be solved further.Therefore,based on the application scenarios of several classical microwave planar transmission lines(TLs),including two-conductor coplanar waveguides(CPWs)and microstrips and substrate integrated waveguides(SIWs),the high-efficiency excitations of SSPPs and manipulating their propagations are investigated in this paper.Aiming to overcome the drawbacks of the practical applications of single-conductor structure in microwave planar circuits,and manipulate the propagations of SSPPs with diversified features,which accelerates the developments of microwave novel functional devices.The SSPP unit cells based on microwave planar TLs are proposed and investigated.The efficient excitations of fundamental and high-order modes of SSPPs are realized.The strategies of manipulating the propagations of SSPPs are also investigated.The propagations with single-band,dual-band and wideband rejection band as well as wideband passband are achieved,respectively.The main contents of this paper are summarized as follows:(1)By investigating the mechanisms of the excitations of fundamental modes of two-conductor SSPPs,a two-conductor SSPP unit cell based on CPWs is proposed.The dispersion properties of the modes supported by the unit are revealed and the impedance of the unit is extracted as well.A smooth transition with CPWs is designed.Simulations and measurements on the transmission characteristics of SSPPs are performed,which verify the mechanisms of high-efficiency excitations of SSPPs.The transmission efficiency at low frequencies are greatly improved(the measured reflection coefficients below 7.2GHz are lower than-10dB).(2)Considering the excitations of high-order modes of two-conductor SSPPs,two kinds of two-conductor unit cells with complementary grooves,which are based on microwave planar transmission lines(including CPWs and microstrips)are proposed.Transitions which can realize seamless connections with microwave planar circuits are also designed.The dispersion properties of high-order mode of SSPPs supported by the unit are analyzed.The high-efficiency excitations of SSPPs and the effective enhancements of operating bandwidths are validated by both simulations and measurements.The bandwidths of high-order modes can be improved from 1.52 GHz and 2.85GHz(corresponding to single-conductor cells)to 11.75 GHz and 11.94 GHz,respectively.The in-band reflection coefficients are lower than-10 dB.(3)In order to manipulate the propagations of SSPPs with bandstop properties,CPW-based two-conductor SSPP unit cells are modified by adding open loop resonators(OLRs).The dispersion properties of the modes supported by units are analyzed and the impedances of units are also extracted.The effects on the rejection bands of SSPPs by the opening directions and locations of OLRs are revealed.The single-band,dual-band and wideband bandstop propagations of SSPPs are verified by simulations and measurements.The operating bands with measured transmission coefficients better than-10 dB are ranging from 5.72 GHz to 5.83GHz(single-band),4.59 GHz to 4.65 GHz and 5.74 GHz to 5.82GHz(dual-band)and 6.67 GHz and 8.47GHz(wideband).(4)The method of manipulating the propagations of SSPPs with bandpass properties are investigated by modifying the dispersion properties of SSPPs.An SSPP unit cell based on a slotted SIW is designed.The dispersion property of the mode supported by the unit is extracted from S parameters and obtained by mode analysis.High-efficiency excitations from microstrips are realized.Both numerical and experimental results validate the manipulating of bandpass propagations of SSPPs.The measured relative bandwidth is as high as 93.9%(ranging from 4.51 GHz to 12.5GHz),the in-band reflection coefficiens are almost better than-10 dB.