Reconfigurable linear-to-circular polarization converter

This chapter presents a novel Polarization Reconfigurable Converter (PRC) designed for converting linear polarization to circular polarization in a transmissive manner. The PRC's basic component constitutes a half-hexagonal geometry and its mirrored counterpart, both printed on opposite surfaces of a substrate with a single layer. The PRC can convert a ϕ = 45° polarized incident wave into either a linearly polarized (LP) or with circular polarization, depending upon whether the diode is in the ON or OFF state, thanks to a PIN diode that is positioned in the center arm of the unit cell. With a total size of 0.046λ₀³ (λ₀ being the wavelength at 15.15 GHz), the PRC is small and achieves a ratio of polarization conversion higher than 0.9 within the 14.0–16.0 GHz frequency range. The reconfigurability of the polarization is confirmed through an array consisting of thirty-six elements of the proposed reconfigurable converter, rotated 45 degrees in a clockwise direction, and placed atop an LP patch antenna. When the diodes of the proposed converter are in the ON condition, the antenna transmits an LP wave, while in the OFF condition, it transmits a CP wave (either left-hand or right-hand circular polarization). Measurement and simulation results for the antenna prototype with the PRC demonstrate strong agreement.