Researches On Electromagnetic Metamaterial Absorber And Polarization Converter

In recent years, the electromagnetic metamaterial has become a very important research direction in the domestic and foreign academic circles. One of the distinguishing features of the metamaterial is that the equivalent permittivity and permeability of the metamaterial can be controlled by adjusting the various geometric parameters of the periodic structure. The metamaterial absorber and metamaterial polarization converter are two of the most metamaterial applications. A narrow band metamaterial absorber, a broadband metamaterial absorber and a broadband metamaterial polarization converter are presented in this paper.In the first part, a narrow band metamaterial absorber which works at low frequency for TE-polarized wave is presented. It is comprised by three structures like word “?”. The substrate is FR4. At frequency from 902.4MHz to 930.6MHz, its absorption is above 90%. The absorptions of different large incident angles are simulated. The theory of absorption is analyzed and the conclusion is that the absorption is mainly cuased by the loss of the substrate.In the second part, a polarization-insensitive broadband metamaterial absorber is presented. It's comprised of four triangles and a wafer. The substrate is F4 B of 3.5mm. The absorption is above 90% at frequency from 7.15 GHz to 16.09 GHz for both TE and TM polarized incident waves. The relative absorption band is up to 77%. We come to a conclusion of absorbing wave at broadband frequency by analyzing the relative impedance, equivalent permittivity and permeability, surface current and electric field of the unit cell. The main innovation points of the proposed metamaterial absorber are broadband absorption and polarization insensitive. The absorption band includes full X band and part of C and Ku bands. A sample is made and tested in the microwave anechoic chamber and the experimental results match well with the simulated results.In the third part, a broadband metamaterial polarization converter is proposed. It is comprised of two partial rings. The substrate is FR4 of 3mm. The reflective polarization conversion ratio is up to 90% at frequency from 9.50 GHz to 15.41 GHz. The polarization conversion band is 5.91 GHz and the relative band is 47.45%. In order to fabricate the converter, the parameters of the unit cell have been modified and the reflective polarization conversion ratio is up to 87.7%. A sample is fabricated and tested in the microwave anechoic chamber and the experimental results match well with the simulated results. The main innovation points of the proposed metamaterial polarization converter are simple structure and high conversion ratio for both TE and TM polarized waves.