Movable Antenna Aided Interference Suppression in Near-Field Environment

Abstract

Movable antennas (MAs) provide additional spatial degrees of freedom (DoFs) for interference suppression by adaptively reconfiguring antenna positions in near-field environment. However, existing MA-based designs fail to suppress mainlobe and grating-lobe interference simultaneously. To address this issue, we propose a two-stage antenna position optimization framework. Specifically, in Stage I, we adopt a beamfocusing-based approach to reduce the array gain at the mainlobe jammer while constraining the inter-element spacing to prevent excessive grating-lobes. Then, in Stage II, we formulate a grating-lobe leakage minimization problem. To efficiently solve the non-convex problem, we develop a trust-region-based successive convex approximation (SCA) algorithm with a dynamic active-set update, which substantially reduces redundant collision-avoidance constraints. Simulation results show that the proposed method can effectively suppress mainlobe and grating-lobe interference, achieve higher achievable rates than fixed-position arrays, and approach conventional AO-SCA performance with significantly lower computational complexity.