Ultra-broadband 90° polarization rotator based on bi-anisotropic metamaterial

A three-layer bi-anisotropic metamaterial (B-AM) is proposed to realize a 90° polarization rotator in an ultra-broadband frequency range of 5.8-11.8 GHz, which can convert the linearly polarized wave into its cross-polarized wave for propagating directions. Simulated and measured results show that the ratio of polarization conversion (PCR) of the three-layer B-AM is nearly 90% and FWHM is more than 68%. In addition, the three-layer B-AM can achieve asymmetric transmission (AT) for forward and backward propagations of linearly polarized waves. The proposed three-layer B-AM has simple geometry and wider operating frequency bands comparing to the previous designs. The physical mechanism of the ultra-broadband linear polarization conversion effect is illustrated by simulated surface current distributions of the structure.