MULTI-BAND CIRCULAR POLARIZER USING ARCHIMEDEAN SPIRAL STRUCTURE CHIRAL METAMATERIAL WITH ZERO AND NEGATIVE REFRACTIVE INDEX

A novel multi-band circular polarizer is proposed by using a bilayered chiral metamaterial (CMM). The unit cell of the CMM is composed of four Archimedean spiral structures, which are twisted 900 to each other in the upper and bottom layers. When a linearly polarized wave incidents on this circular polarizer, the simulation result shows that the transmission of right circularly polarized (RCP) wave can be obtained at 14.28 GHz and 15.96 GHz, while the transmission of left circularly polarized (LCP) wave is emitted at 15.3 GHz and 16.88 GHz. The retrieval results reveal that the effective refractive index of the CMM closes to zero or negative at the vicinity of four resonances. The experimental results are in good agreement with the numerical results.