The fabrication and design of a liquid crystal (LC)-based X-band reflectarray antenna are described. A high-efficiency reflectarray antenna was achieved by defining and optimizing its efficiency parameters. Considering the high loss tangent of the LC, the equivalent circuit of the lossy medium was modeled, and the reflection loss of the unit cell was minimized. Furthermore, a 2×2 patch array antenna was employed to optimize the spillover and taper efficiency. To minimize blockage loss, the reflectarray was designed by employing offset feeding, resulting in an aperture efficiency of 26 % in the broadside direction. Measured beam patterns were obtained by changing the applied bias voltage, and the simulated results were obtained by changing the permittivity of the LC. Consequently, the permittivity of the LC was determined by comparing the measured and simulated results.