Ultra-Thin Metasurface Polarization Converter with Linear and Circular Polarization Features for RCS Applications

In this study, an attractive ultra-thin metasurface (MS) converter is proposed for both K-band (18-27 GHz) and Ka-band (27-40 GHz) having the superior performance of the linear-to-linear polarization (LP-LP) conversion and the linear-to-circular polarization (LP-CP) conversion. Its operating bandwidth for the LP-LP conversion is approximately over 18.6-26.7 GHz (lower part of the K-band) with a conversion efficiency of more than 90% and over 19.55-24.8 GHz (upper part of the K-band) with a polarization conversion ratio (PCR) value of more than 99%. In addition, its operating bandwidth for the LP-CP conversion (a left-handed circular polarization (LHCP)) is nearly between 31.8 and 40.5 GHz (Ka-band) with a PCR value of more than 99%. The converter can achieve a PCR value greater than 90% for both the LP-LP and LP-CP conversions for an oblique incidence wave with an incidence angle up to 40 degrees\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ 40<^>\circ $$\end{document}. The design also provides mono-static radar cross section for the 18.6-26.7 GHz frequency range, where the LP-LP conversion is provided. The proposed structure can be considered to be ultra-thin having a thickness of 1 mm corresponding to 0.075 lambda\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lambda $$\end{document} in the LP-LP and 0.12 lambda\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\lambda $$\end{document} in the LP-CP cases concerning the center frequency. The cost-effective bandwidths (BWCEs) are 210 and 34 for the LP-LP and LP-CP conversions, respectively. Free-space experiments were carried out at X-band and Ku-band to validate our design.