Research On Tunable Absorber Based On Metasurface

Electromagnetic metasurface is an artificially designed subwavelength structure,which can exhibit excellent ability to control electromagnetic waves.By designing and changing the unit structure and periodic arrangement of the metasurface,its electromagnetic properties can be controlled.Electromagnetic properties that materials do not possess,thus enabling engineering applications.Although metasurfaces have been proposed and studied for decades,they still attract the attention of scientists and engineers due to their remarkable advantages in controlling electromagnetic waves,especially in the absorption and polarization of electromagnetic waves.In this paper,research on multi-band and tunable metasurface absorbers is carried out.The specific work is as follows:(1)A double-band metasurface absorber is designed.First,a metasurface composed of circular and triangular structures is proposed.The absorption rate of this structure to incident electromagnetic waves is as high as 98.1%and 99.8%at the two operating frequencies of 10.11GHz and 15.63GHz,respectively.Sensitive and wide-angle stabilization characteristics.The equivalent circuit of the device is studied,and the working principle of the absorber is studied based on the electric field and surface current distribution.(2)A three-band tunable metasurface absorber is designed.Based on the above-mentioned structural extension design,the device introduces a varactor diode into the circular and triangular metal patches of the metasurface,and realizes the bias control of the varactor diode by adding metal vias.The designed absorber unit structure size isλ/2.75×λ/2.75×λ/16.5,whereλis the wavelength of the absorber at the lowest operating frequency.The absorber has three absorption frequency bands,and the absorption rate and operating frequency are regulated by the bias voltage of the varactor diode:as the reverse bias voltage increases(0-19V),the frequency of the first absorption peak shifts Up to1.0GHz(7.2-8.2GHz),the absorption rate increases from 88.1%to 99.9%;for the second absorption peak,the frequency shift is 0.47GHz(10.93-11.4GHz),and the absorption rate exceeds 99.2%;while the third The frequency shift of each absorption peak is 0.26GHz(15.84-16.1GHz),and the perfect absorption rate is maintained above 99.8%.Finally,the absorbing mechanism of the structure is analyzed by the equivalent circuit and surface current distribution,and the reliability of the results is verified by experimental tests.(3)A metal-graphene-based tunable terahertz metasurface absorber is designed.The absorber unit structure is composed of square ring metal and cross-shaped graphene.By controlling the Fermi level of graphene,the absorbing frequency band of the absorber can be adjusted.The simulation results show that when the Fermi level E_Fincreases from 0e V to 0.5e V,the operating frequency of the metasurface device is shifted from 0.48THz to0.99THz,and the absorption rate of electromagnetic waves remains above 99.4%.Finally,the working mechanism of the absorber is studied by analyzing its resonance and wave absorption characteristics.