The Antenna Enhancement And Design Of Multifunctional Devices Based On Metasurface

In the past few years,metamaterial becomes a hot spot in the electromagnetic field with the fancy properties that traditional materials in the nature do not have.Metamaterial is composed of subwavelength cells.It is widely used in various disciplines and fields with the ability of regulating electromagnetic waves.Early studies focus mainly on three dimensional structures,which suffer the shortcomings of heavy volume and big loss.So the practical applications of metamaterials are limited.Metasurface is the two-dimensional form of metamaterial,and it has gradually replaced the metamaterials in lots of applications because of its ultrathin structure,setting off a new study.Metasurfaces possess the capacity of controlling electromagnetic wave phase,amplitude as well as the polarization mode,and this paper will design several novel metasurfaces to realize the antenna enhancement and multifunctional devices.The specific content and innovation points has several following aspects:1.Study the non-resonant metamaterials in the role of the antenna.The designed metamaterial structure is composed of three half-ring units,revealing the non-resonant effect within the Ka-band.According to the effective medium theory,it can be seen as the homogeneous medium and the effective electromagnetic parameters are extracted through the scattering parameter inversion method.After loading the metamaterials on the log periodic antenna,there is a gain enhancement of 3.6dB without sacrificing other parameters of the antenna.Meanwhile,the gain fluctuation over whole frequency is reduced,which is conducive to be used in the wireless system.The design can also be used in the terahertz frequency.2.Design a novel multi-frequency multi-functional metasurface and study its properties.Based on the properties of C-shaped opening resonate ring,a bi-functional metasurface is proposed,which can simultaneously achieve anomalous reflection and refraction at two terahertz frequencies.The reflection and refraction modes are regulated by two different resonators respectively,with mutual independence.By analyzing the phase responses and amplitude responses of two modes,a six-unit array and an eight-unit array are designed.For the six-unit array,the phase difference is 60°,the reflection amplitude and refraction amplitude is 0.8 and 0.38,respectively;For the eight-cell array with phase difference of 45°,its reflection amplitude is 0.6,and the reflection amplitude is 0.4.3.Design a number of multi-functional metasurface deflectors and lens.The onedimensional metasurface deflector realizes the anomalous refraction and reflection when working at the lower frequency and the higher frequency,respectively;The twodimensional metasurface deflector achieves different deflection functions under different polarization modes.With the ability of manipulating phase and amplitude,metasurface not only can be used to realize the beam bending,but also focusing.By accurately adjusting the phase values of each unit,the designed meta-lens achieves focusing effect at the two specified frequency.For bi-foci lens,two focal points are set as ten times the wavelength and three times the wavelength,therefore the transmissive bi-foci effect and the reflective bi-foci effect can be observed at the lower frequency and higher frequency points,respectively.