Broadband linear‐cross and circular‐circular polarizers with minimal bandwidth reduction at higher oblique angles for RCS applications

Abstract

In this work, broadband linear to cross and circular to circular polarization converter for K and Ka-band applications is proposed. The metasurface comprises a novel H-shaped unit cell printed on 1.2 mm thin FR-4 grounded dielectric substrate. It exhibits 90% polarization conversion ratio (PCR) over a bandwidth of 22.26 GHz (17.97-40.23 GHz) with 76.5% FBW maintaining a minimal PCR of 92.5%. The converter also maintains handedness for circularly polarized incident wave. Surface current distributions at different resonant frequencies are analyzed to illustrate the reason behind the broadband behavior. The converter design is simple with the cell periodicity of 0.209λo and thickness of 0.071λo, where λo is the free-space wavelength corresponding to the lowest frequency of the band. Monostatic and Bistatic RCS analysis of the designed converter is performed, demonstrating greater than 10 dBsm RCS reduction over all the frequency range. It shows ~16 to 30 dBsm at resonant peaks in comparison with PEC. To the best of the authors' knowledge, the proposed structure shows broadband response with angular stability up to 40° for both TE and TM with less bandwidth reduction (up to 30%) at higher oblique angles without compromising the compactness and performance of the cell.