| Metamaterials (MMs) are one type of novel artificial electromagnetic materials. They have opened a new research domain for electromagnetic field. MMs have a huge application prospect in the fields of satellite communications, navigation, radar, medical imaging and so on. MMs have great potential for modulating the optoelectronic information, so the preparation, optical characteristics and application of the metamaterials are currently the research hotspot.This paper presents a study of polarization transformer’s model design based on Chiral Metamaterial (CMMs). The theoretical analysis, simulation and experiment have been taken to discuss the electromagnetic properties of CMMs and look for a simple and effective design method.Three new metamaterial structures have been designed for polarization rotator. The first model is based on split-ring resonators(SRRs), this metamaterial is composed of dielectric substrate and metal backplane, and it can completely convert incident linear-polarized waves into circular-polarized waves, elliptic-polarized waves and linear-polarized waves whose polarization is perpendicular to the incident wave. The second model is an asymmetric chiral metamaterial which is constructed by using a pair of planar spiral structures. The metamaterial is composed dielectric substrate and one pair planar spiral with a certain twisted angle. Numerical simulation results show that when an linearly polarized wave incidents on this designer, the electric field is transformed into left circularly polarized wave at15.25GHz, while right circularly polarized wave at15.93GHz. Furthermore the right ellipse polarized wave is excited at18.09GHz. Effective parameters of this structure, including polarization azimuth and elliptical are obtained from simulated. The results shows that the material get circular dichroism and optical activity. The last model is a novel multi-band circular polarizer which is proposed by using a bilayered chiral metamaterial. This metamaterial can manipulating transmitted wave polarization with low loss. The simulation result shows that the transmission of right circularly polarized wave can be obtained at14.28GHz and15.96GHz, while the transmission of left circularly polarized wave is emitted at15.3GHz and16.88GHz. The surface current distributions at the four resonant frequencies are analyze, we can get the phenomenon similar electric dipole and magnetic,which gives a theoretical support. in addition, the experimental results are in good agreement with the numerical results. The electromagnetic parameters of negative refractive index materials that need to characterized are analyzed, including transmission spectrum of RCP/LCP wave, refractive index of RCP/LCP wave tradintional, chirality parameters, relative dielectric constant and relative magnetic permeability.Through these researches, chiral metamaterial shows broad application prospect and research value at electromagnetic protection and ECM. |
