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Abstract
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A reflective linear-to-circular polarization converter based on dual frequency-selective structures (FSSs) is proposed and modeled to exhibit efficient wideband performance. The design
utilizes a diagonal array of two connected circular patches as an effective anisotropy with
regular current distribution in several successive resonances, resulting in orthogonal reflections with a 90∘ phase difference. The relevant upper-part characteristic is improved by using
two separate square patches as a high-frequency resonator. This design with distinct key
parameters leads to high overlapping and then excellent bandwidth and efficiency over 105%
and 96%, respectively, with an axial ratio below 1.7 dB. A sophisticated equivalent circuitadmittance model including effective mutual coupling between two FSSs is extracted, featuring
closed-form equations for the physical design. Different dielectric constants are studied on the
converter, which offer controllable coverage in the range of 3–24 GHz (S, C, X, Ku, and K
bands), variably. For actual validation, a very thin (0.04𝜆0 at 3.65 GHz) 8 × 8 array prototype was built and measured at different incident angles, showing angular stability up to 45∘
in 78% (6–14 GHz) bandwidth. This converter has potential applications in communication,
spectroscopy, detection, and imaging in micro-, mm-, and THz-wave regions.
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