Beam Squint Mitigation in Movable-Element STARS-Aided Near-Field Communications

A novel movable-element simultaneously transmitting and reflecting surface (ME-STARS)-aid near-field wideband communication framework is proposed. In particular, the position of each STARS element can be adjusted to combat the significant wideband beam squint issue in the near-field communication instead of using costly true-time delayer (TTD) components. To reveal the fundamental design insights, two practical element movement modes, i.e., 1-D movement and 2-D movement, are proposed. On this basis, a multi-user near-field wideband downlink communication scenario is considered, where a sum array gain maximization problem is formulated by optimizing the STARS element positions. To solve this intractable problem, the particle swarm optimization-based heuristic search method is employed to determine the desired element positions. Numerical results demonstrate that the ME-STARSs can effectively address the beam squint for near-field wideband communications, and 2D movement mode achieves performance comparable to TTD.