Dual-Patch Polarization Conversion Metasurface-Based Wideband Circular Polarization Slot Antenna

In this paper, a novel polarization conversion (PC) structure is introduced, and its use with a wideband, wide 3-dB axial-ratio (AR) beam, low-radar-cross-section (RCS) circular polarization (CP) slot antenna is suggested. The unit cell of the proposed PC metasurface (PCM) consists of square and
$L$
-shaped patches separated by an
$L$
-shaped slot printed on an FR4 substrate. The mechanisms for linear to circular polarization and bandwidth improvement of a conventional antenna are analyzed theoretically. Through numerical optimizations and parametric studies, a simulated 10-dB impedance bandwidth of 42.7% (4.15–6.4 GHz) and a 3-dB AR bandwidth of 26.2% (4.8–6.25 GHz) are achieved by the proposed antenna. As the simulation demonstrates, the proposed antenna achieves an average 20-dB RCS reduction in a wide band from 5.25 to 6.8 GHz compared with a conventional slot antenna covered by the PC band. In addition, compared with the previously reported work, the PCM-based CP antenna exhibits a larger 3-dB AR beam width of 200° in the
xoz
plane and 120° in the
yoz
plane, and a wider CP bandwidth within the operational bandwidth. Finally, an overall volume of
$0.55\lambda _{0}\times 0.55\lambda _{0}\times 0.05\lambda _{0}$
centered at 5.275 GHz is fabricated and measured, demonstrating good agreement with the simulation results.