Novel Dual-mode Reconfigurable Polarizer for Wideband Linear-Circular Transmission and Reflection Operating in Same Frequency Band

This study explores a novel wideband reconfigurable polarizer for K/Ka-band applications. The design consists of two metallic layers: two frequency selective surfaces printed on either side of the low-loss dielectric substrate. Here, the RF pin diode is mounted on the backside of the substrate for switching the device state electronically. The polarizer converts the linearly polarized signal into a circular one with a 3 dB Axial Ratio from 19-28.52 GHz during transmission (OFF state) and 23.87-30.12 GHz during reflection (ON state). In addition, it can convert into cross-polarization with an effective 90% Polarization Conversion Ratio from 32.04-43.96 GHz in reflection mode. The Transfer Matrix Method is used to analyse the polarization conversion mechanism. Surface current distributions can easily demonstrate plasmonic resonances responsible for this multiple conversion. The design performance is investigated for different oblique angles under Transverse Electric (TE) and Transverse Magnetic (TM) modes. The proposed polarizer is compact and occupies an electrical dimension of $0.152\lambda_{L} \times 0.190\lambda_{L}$ and an overall thickness of $0.051\lambda_{L}$. Here, $\lambda_{L}$ is the free-space wavelength corresponding to the lowest operating frequency. The design novelty lies in its compactness and the different polarization conversions in the reflection and transmission operating in the same frequency band with better angular stability.