Multi-band metamirrors for linear to circular polarization conversion with wideband and wide-angle performances

Abstract

Multi-band operation of the elements of electromagnetic systems can result in merging multiple systems and cost reduction. A challenge for multi-band operation is the circular polarization which is frequently a requirement for these systems. However, circular polarization can be obtained from linearly polarized waves using transmission-mode or reflection-mode linear to circular polarization converters. Therefore, advanced multi-band reflection-mode linear to circular polarization converters are proposed in this paper. Two versions of the polarizers are designed with different design methodologies. The first polarization converter has 3 dB axial ratio bandwidths of 29.3, 21.8, and 7.6% on 2, 8, and 12 GHz with 15° permitted incident angle difference. The second polarization converter with incident angle range of 25° ($\theta _{{{\text{min}}}} = 23^\circ$ and $\theta _{{{\text{max}}}} = 48^\circ$) has 17.8, 10, and 22.5% bandwidths on 2, 5.5, and 8 GHz, respectively. In addition, the bandwidths can be improved to 32.1, 28.3, and 26.5% by reducing the incident angle range to 10° with $\theta _{{{\text{min}}}} = 30^\circ$ and $\theta _{{{\text{max}}}} = 40^\circ$. Finally, a prototype of the second polarization converter is fabricated and simulations are met by measurement results.