Contents I. Introduction
Antennas that can steer the radiation beams are critical components in low Earth orbit satellite communications [1]–[3]. They are often designed by creating a progressive phase variation of the radiated fields. The progressive phase distribution can be implemented mainly in electrical, mechanical, or hybrid ways. Generally, electrical steering antennas use phase shifters at each array unit to realize fast scan ability, but the cost of active phase shifters is very high [4], [5]. Mechanical steering antennas have better radiation performance and wider scan coverage, but they suffer from the slow scan speed and bulky servomechanisms. Therefore, lots of efforts were devoted to hybrid designs [6]–[9]. Among these compromised solutions, lens antennas based on metasurfaces have attracted the attention of many groups for their advantages of low cost, low profile, ease of integration, and so on [10]–[13].
