On the Paraxial Approximation and Phase-Gradient Methods for Risley Prism Inspired Beam-Steering Metasurface Antennas

This paper presents the study of the two methods for the beam-steering planar metasurface antennas based on optical Risley Prism scan theory: paraxial approximation and phase gradient methods. A two-dimensional (2D) beam-steering antenna is first developed, consisting of two planar metasurface transmit arrays and a linearly polarized (LP) horn. The two transmitarrays have identical constant phase delay gradients, and the beam steering capability is realized by mechanically rotating the two independent metasurface transmitarrays. The antenna developed is then used to compare and verify the precisions of the paraxial approximation method and the phase method. Simulation results show that the phase method is more accurate than the paraxial approximation method, especially with large phase delay gradients.