Unit Cell Arrangement Analysis for Focusing Metasurfaces

When designing a metasurface or reflectarray antennas, we need to arrange different unit cells according to the desired continuous phase profile. Since the limited phase response of the unit cell, one usually constructs the database by selecting unit cells with different geometrical details whose phase responses cover 2 pi range. It is inevitable that a periodic phase trip point occurs, leading to the abrupt size variation of adjacent unit cells. In this paper, we design three similar metasurfaces with phase trip points at different places, and analyze their influence on the focusing performance. It is demonstrated that the position of abrupt unit cell has little effects on focal length, but is influential in side lobe levels.