Anisotropic Metallic Grating With an Inhomogeneous Superstrate as a Broadband Reflective Polarization Converter: Design and Fabrication

ABSTRACT

A broadband reflective Linear‐To‐Circular Polarization (LTCP) converter is proposed in this work. Such a mechanically simple structure converts a linearly polarised incident plane wave into a circularly polarised reflected one with a minimum loss. In its design, an anisotropic metallic grating printed on the interior side of an inhomogeneous superstrate is utilised. Each re‐radiating element of this array is composed of a double concentric ring in which the inner ring is attached to two arc lines. The inhomogeneous superstrate, formed by a low‐cost FR4 dielectric slab with periodically drilled air holes to reduce structure loss, is mounted above a copper plane with an optimised spacing to minimise reflective wave loss. The dimensions of its unit cell are 10.6 × 10.6 × 1.8 mm ³ (0.25 λ  × 0.25 λ  × 0.043 λ ), where λ represents the free‐space wavelength of the lowest frequency in the operating bandwidth. To validate the numerical results, the designed structure with 12 × 7 cells is fabricated and tested. Measurements demonstrate the Axial Ratio (AR) < 3 dB, indicating near‐ideal circular polarization and the Polarization Conversion Rate (PCR) approaches unity within 7.2∼12.6 GHz. Such a structure can be used in various applications, such as weather monitoring multi‐beam/beam scanning antennas, wireless/radar tracking and navigation systems.