Optically Transparent Reflectarray Based on Indium Tin Oxide With Improved Efficiency

Indium tin oxide (ITO) material is a practicable alternative to metal utilized in transparent antennas. However, the conductor loss of ITO material is the major obstacle to antenna design. In this communication, an optically transparent reflectarray based on glass substrate with ITO film operating at 28 GHz is presented. A novel subwavelength element operating in hybrid modes with 0.167λ
₀
(λ
₀
is the free-space wavelength at 28 GHz) spacing is proposed for transparent reflectarray design. The peak loss of the proposed element is below 3.4 dB and a phase variation of 420° is achieved at 28 GHz. A 54 × 54-element reflectarray with a focus to diameter ratio (F/D) of 0.7 is designed and simulated for demonstration. It achieves radiation efficiency higher than 73% at the center operating frequency. The proposed reflectarray is verified by the measurements, which is reasonably consistent with the full-wave simulated results.