Analysis And Design Of Antennas Based On Spoof Surface Plasmon Polaritons

Spoof Surface Plasmon Polariton(SSPP)is a novel meta-material,which is used to control electromagnetic waves.It is a two-dimensional surface structure composed of subwavelength structural elements arranged periodically or quasi-periodically.Compared with three-dimensional meta-materials,SSPP has the advantages of small size,low profile,and easy conformality.Compared with traditional uniform transmission lines,SSPP has greater slow-wave properties,which can achieve high equivalent constant properties on low dielectric-constant dielectric substrates,that is,when electromagnetic waves propagate in them.The wavelength is shorter than that of the uniform structure,so it can be used to design miniaturized filters and transmission structures.In contrast to real high-k dielectric substrates,SSPP has better design flexibility,while using it to design miniaturized devices,it can achieve slow-wave characteristics in one direction(a larger equivalent dielectric constant)while maintaining the characteristics of the low dielectric constant in other directions,which is more conducive to the design of the antenna.Based on the phase characteristics of SSPP,this paper explores its effect on the resonant frequency of the antenna and designs several types of antennas based on SSPP.The main research contents and contributions of this paper are summarized as follows:1).Miniaturized linearly polarized rectangular patch antenna based on SSPP: We propose a general design method to design a miniaturized patch antenna without affecting the antenna radiation effect and verify the rationality of the method through experiments.We first analyzed the slow-wave characteristics of SSPP and carried out a miniaturization design without affecting the antenna radiation effect.It has been verified that after substituting the existing calculation method for fitting the resonant frequency and operating bandwidth of the antenna into the correction factor of the equivalent dielectric constant,the calculated resonant frequency and operatingbandwidth of the miniaturized antenna based on SSPP are related to the finite element electromagnetic simulation results.and the radiation pattern of the proposed miniaturized antenna based on SSPP is similar to that of the traditional patch antenna,so the proposed design method of miniaturized antenna based on SSPP is compatible with the existing related technologies for analyzing patch antennas.2).Designing of circularly polarized patch antenna based on SSPP,we propose a design method of designing a miniaturized circularly polarized patch antenna,which extends from the design method of the previous chapter for miniaturized linearly polarized antenna to design circularly polarized antenna.We can determine the size of the antenna through the phase characteristics.By adjusting the coupling degree between a pair of orthogonal modes with a phase difference of 90°,we can adjust the axial characteristics at the center frequency of the miniaturized circularly polarized patch antenna,and then realize the miniaturization of the circularly polarized patch antenna.3).Designing of miniaturized MIMO(Multiple-Input Multiple-Output,MIMO)antenna based on SSPP,we propose a method that does not require additional decoupling structures to design miniaturized MIMO antennas.We first analyze the influence of the slow wave effect of SSPP on the size of the antenna.When the antennas’ arms are designed by SSPP with a larger equivalent dielectric constant,the antenna elements can be designed to be miniaturized.Not only that,there are two coupling paths between the MIMO antenna elements: one coupling path passes through the adjacent antenna arms,and the other is coupled through the ground plane.The equivalent phase constants of the two coupling paths are different.When the phase difference between the two coupling paths reaches is 180°,a coupling zero point can be achieved,so that the two miniaturized antennas can realize good isolation without additional decoupling structures.4).Designing of the miniaturized pattern reconfigurable Yagi antenna based on the active SSPP,we propose a method to design the Yagi antenna director and reflector with the active SSPP.We control the equivalent dielectric constant of a section of the SSPP strip by controlling the states of the PIN(positive-intrinsic negative diode,PIN)diode,thus changing the resonant frequency of the SSPP strip,thereby changing the reactance of the SSPP strip at the center frequency.In the design step,we first analyze the impedance of the traditional microstrip structure dipole driver element at the center frequency.Then a pair of active SSPP parasitic strips in different states are used as the director and reflector of the Yagi antenna,respectively.Since the director and reflectorof the Yagi antenna have reactances of opposite polarities,when we change the reactance of a pair of parasitic strips of the Yagi antenna,we can switch the director and reflector of the Yagi antenna to achieve the reconfigurable of the pattern.Since the length of the director and reflector designed by this method is shorter than that of the traditional Yagi antenna,the pattern reconfigurable Yagi antenna designed by this method is compact in size.