Research On Dual-Band And Broadband Controllable Metamaterial Absorbers

With the rapid development of modern microwave electronic technology,electronic products not only bring convenience to public life,but also cause electromagnetic(EM)pollution and interference.Noise pollution,air pollution,water pollution and EM wave pollution has been listed as the four major public hazard threatening human survival by the World Health Organization.The EM absorbers can absorb the energy of the incident wave in the designated working frequency range and then effectively alleviate the EM pollution and interference caused by various electronic products.The size of traditional EM absorbers are large,which limits its application to some extent.Due to the advantages of small size,high absorptivity and low cost,metamaterial(MM)absorbers have attracted extensive attention from scholars at home and abroad.At present,MM absorbers are mainly developed in the direction of ultra-thin,multi-frequency,broadband,polarization insensitive and frequency-controllable.This article focuses on the frequency-controllable MM absorbers.The main contents of this paper are summarized as follows:1.A dual-band tunable MM absorber is proposed.The unit cell of the absorber is composed of open square ring and the open I-shaped resonant structure.Varactors are loaded at the opening,and the dual-band tunability is realized by changing the reverse bias voltage of the varactors.As the reverse bias voltage of the varactors changs from 0 V to-20 V,the simulation results show that the dynamic adjustable ranges of low frequency and high frequency are 2.51-3.37 GHz and 3.66-5.23 GHz,respectively.The frequency tuning ratio(FTR)are 29.3%and 35.3%,respectively.2.A dual-band switchable MM absorber is proposed.The unit cell of the absorber is composed of two open square ring resonators with different sizes.Semiconductor diodes are embedded in the opening,and the frequency is switchable by changing the states of the diode.The size of the absorber unit cell is 15×15×1.6 mm³(0.155?₁×0.155?₁×0.017?₁,where?₁is the free space wavelength at low frequencies).The simulation results show that,under vertical incidence,different dual frequency bands(3.1/5.6GHz,3.1/8.4GHz,5.5/6.6GHz,5.3/8.4GHz)can be switched by controlling different combination states of the switches.The absorber has the characteristics of wide-angle absorption and polarization insensitivity,which can be used in fields such as EM pollution,radar technology,and biological sensing.3.A broadband switchable MM absorber is proposed.First,a dual-band MM absorber is designed.The unit cell of the absorber is composed of a circular ring resonator and a hybrid resonator consisting of an open circular ring and a cross-dipole.The simulation demonstrated that,under normal incidence,the absorber provides two distinct absorption at 5.38 GHz and 7.0GHz,with the peaks of 99.31%and 98.39%,respectively.The half-peak widths are 200 MHz(5.28-5.48 GHz)and 240 MHz(6.88-7.12 GHz),respectively.Secondly,the open ring and the open Jerusalem cross resonant structure composed of the open ring and the open cross band are loaded at resistors to achieve wideband absorption.The absorber has a absorptivity of more than 80%between 3.44 GHz and 13.34 GHz,and the relative bandwidth is 118%.Finally,the switchable ground layer is introduced,and the frequency reconfigurable broadband switchable is realized by loading PIN diodes.The measurement results show that when the diodes are turned on,the absorptivity of the absorber from 3.45 GHz to 15.17 GHz is more than 80%;when the diodes are off,the absorptivity of the absorber at3.11-4.21 GHz and 5.98-14.27 GHz is above 80%.The electric field distribution is analyzed and its absorption mechanism is further explained.