Broadband Double Layer Metamaterial Circular Polarizer Based on H-Spiral Structure

A broadband double layer metamaterial circular polarizer using H-type spiral structure is proposed. The metamaterial structure consists of 784 unit cells arranged in a 28 x28 layout. Each unit cell is composed of H-spiral structure which are twisted by an angle of ± 45 ^o . The right handed circular polarization (RHCP) and left handed circular polarization (LHCP) with high transmission circular polarization are achieved at 27.95GHz-29.95GHz, 31.04GHz-34.31GHz, 35.26GHz-35.96GHz, 38.08GHz-38.58GHz, 39.46GHz-39.60GHz, and 29.96GHz-31.03GHz, 34.32GHz-35.25GHz, 38.59GHz-39.45GHz, respectively. In addition, the broadband axial ratio bandwidth of 5.0%, 2.67%, 8.17%, 2.32%, 1.75%, 1.25%, 2.15%, and 0.35% is achieved across the 20–40 GHz range. The prototype model is fabricated and measured for the validation of simulated results. The simulated and measured results reveal that the metamaterial structure have efficient performance, in terms of Axial Ratio, broadband, transmission loss and circular dichroism for advanced polarization conversion applications. The overall calculated axial ratio bandwidth of 23.66% is extracted across the 20–40 GHz.