Scanning Range Expansion of Planar Phased Arrays using Metasurfaces

We propose a novel method to extend the scanning range of planar phased arrays based on a phase gradient metasurface. The phase gradient metasurface is developed by the generalized Snell's law, which can irregularly tailor the direction of propagation of the traversing electromagnetic waves. The proposed transmission gradient phase metasurface (TGPMS) uses bidirectional expansion of the scanning range in a phased array application. The TGPMS consists of periodic and multilayer subwavelength elements that contribute to a wide range of transmission phase shift and multiple incident angular stability. The design is verified experimentally with a compact microstrip phased array that is integrated with the proposed TGPMS. Results demonstrate that the TGPMS extends the scanning range of the integrated array symmetrically, from [-36°, 38°] to [-56°, 60°]. The proposed TGPMS has additional desirable characteristics, such as high transmission, polarization insensitivity, tunable transmission phases in a wide range, and transmission phase stability for waves incident at different angles.