Radiation Manipulation Of Electromagnetic Waves Based On Metasurface

Metasurface is a kind of artificial planar electromagnetic material composed of a series of sub-wavelength unit cell.Its powerful and flexible ability to control electromagnetic waves makes it a research hotspot in the electromagnetic field.In this dissertation,spoof surface plasmon polaritons(SSPP)and phase-tuning metasurface for controlling radiation of electromagnetic waves are deeply studied.The main researches of this dissertation are as follows:1)A wide-angle frequency-controlled beam-scanning antenna based on standing-wave of SSPP is proposed.The antenna is constructed by placing two rows of circular patches at both sides of an SPP waveguide.The SSPP waveguide is designed specially to support standing-wave modes within operating band.According to the proximate coupling mechanism,SSPP modes can be converted to radiated waves by assigned circular metal patches.Simulated and measured results validate that the proposed antenna achieves wide scanning angle of 83° from 9.2 to 16 GHz and gains in whole band are above 10.3d Bi.2)A unidirectional beam-scanning antenna is proposed.The antenna is constructed by placing a series of circular radiating elements on the back of a corrugated metal–insulator– metal(CMIM)supported SSPP waveguide.The CMIM structure is introduced not only as a waveguide for SSPP transmission but also as a reflected to suppress the downward radiation.Both simulated and experimental results show the unidirectional beaming-scanning function is achieved.3)A method for suppressing radiation from chip is proposed.A radiation-suppression structure is designed based on slow-wave feature and dispersion characteristic of SSPP.The structure can convert the space wave radiated from the chip to evanescent SSPP mode in the near-filed region,restraining the energy on the surface of the structure to suppress the radiation.4)An approach to producing the orbital angular momentum(OAM)based on spoof localized surface plasmons(SLSP)is demonstrated.The fundamental and high-order modes of spoof LSPs occur when a textured metallic surface is excited with a microstrip line.Two orthogonal modes of spoof LSPs with +90° or-90° phase retardation are superimposed,resulting in a OAM-vortex mode.By loading a circularly arranged dipole array on the spoof LSPs,the confined surface waves of the spoof LSPs can be converted into radiated vortex waves.Both simulated and experimental results validate the proposed can generate OAM with high purity.5)A phase-tuning metasurface is proposed,and the realization of circularly polarized antenna and OAM generator based on the metasurface are demonstrated.The unit of metasurface is structured by a ring-circled bowtie-like patch having different phase response by varying the size.Units are arranged on a cylindrical grounded dielectric slab fed by a coaxial probe in the center.The size of the unit at different positions is determined by its phase requirements.Both simulated and experimental results validate that the circularly polarized antenna,having good compactness,wide bandwidth and low axial ratio,and OAM emitter is achieved using the proposed phasing-tuning metasurface.