Broadband Asymmetric Circular Polarizer Based on Metamaterial Spiral Structure

This paper introduces a broadband asymmetric circular polarizer based on a metamaterial spiral structure. The proposed metamaterial structure is designed in a 28x28 array, achieving both right-handed circular polarization (RHCP) and left-handed circular polarization (LHCP) with high transmission efficiency at multiple resonant frequencies. Axial ratio bandwidths of 5.05%, 2.67%, 8.17%, and 2.15% are obtained within the 20–40 GHz frequency range. To validate the simulated results, a prototype model was fabricated and measured, showing a strong correlation between simulation and experimental data. The structure demonstrates excellent performance in terms of axial ratio, wideband characteristics, low transmission loss, and circular dichroism, making it well-suited for advanced polarization conversion applications. These features make it highly suitable for advanced polarization conversion applications. Overall, the design achieves an axial ratio bandwidth of 18.0% across the 20–40 GHz frequency range.