This paper presents a high-efficiency 1-bit reconfigurable reflectarray antenna (RRA) based on sub-wavelength unit cell of ring patch in X-band for electronic beam-scanning applications. The aperture efficiency is maximized by optimizing illumination, spillover, and quantization efficiencies. By careful investigation of the feed structure, the aperture efficiency is optimized. The focal diameter ratio (F/D) of 0.36 is selected, resulting in a low profile RRA. In addition, the quantization efficiency is optimized by applying the reference phase shift. The aperture efficiency was measured to be 28% at 9. S5 GHz (in X-band). A wide beam scanning angle of ±60° was also measured in both xoz and yoz planes.