Design of a wide band metasurface as a linear to circular polarization converter

In this paper, we present a wide band metasurface (MS) polarization converter which converts a linearly polarized signal to a right-handed or left-handed circularly polarized signal both numerically and experimentally. The unit cell of MS has three nested rectangular resonators which have two metallic patches at its crossed corners. The simulated and measured results are achieved by a commercial full wave EM simulator and a vector network analyzer with two horn antennas in microwave frequency regime. The S-parameters are obtained for co-polarized and cross-polarized responses and axial ratio is evaluated by the division of these two responses. The axial ratio is kept below 3 dB for efficient polarization converting activity. Correspondingly, axial ratio bandwidth of 800 MHz is obtained. The proposed MS can easily be fabricated and integrated into many desired applications by proper configurations depending on the application area and frequencies. The proposed MS has potential such as polarization converter with 0.75 efficiency in WiMAX frequency band, PMC-like treatment with a phase reflection around 0 degrees and reflection coefficient nearly unity at some frequency points. Beside this, the three nested rectangle MSs also provide opportunities to design low profile antennas with conversion characteristics.