Dielectric Metamaterial-Based Impedance-Matched Elements for Broadband Reflectarray

A dielectric metamaterial-based broadband impedance-matched reflectarray element is presented. The dielectric metamaterial is composed of an impedance-matching layer and a phase-shifting layer. First, the impedance-matching layer is critical for achieving a linear reflection phase response in a broad bandwidth. Full 360° reflection phase variation can be derived by changing the effective permittivity of these two layers. Then the perforated dielectric structures are used to achieve the desired permittivity variation. The specific air hole sizes are accurately determined by treating the perforated structure as dielectric metamaterials. Finally, a reflectarray antenna with an aperture of 300 mm and operating frequency around 13.5 GHz is designed and validated. The measured results show that the proposed impedance-matched reflectarray can operate over a broad bandwidth with the measured maximum gain of 30.3 dBi with 1-dB bandwidth over 12.6–15.1 GHz or 18.1% as well as the measured aperture efficiency of higher than 40% over 11.3–14.2 GHz or 22.8% with a peak aperture efficiency 45.6% at 13.5 GHz.