Electromagnetic-Aware Fluid Antenna Array

2026-07-23

AI Summary

This work addresses the common oversight of electromagnetic coupling in compact fluid antenna array designs, which often leads to inaccurate performance predictions. The authors propose an electromagnetic-aware current-domain modeling framework that unifies position-dependent multi-port impedances, mutual coupling, radiated/received power, source voltage constraints, and channel dynamics, explicitly embedding coupling effects into the optimization process as a usable design degree of freedom. Leveraging a closed-form half-wave dipole model—compatible with full-wave simulations or measured data—the method employs an alternating optimization strategy to jointly solve a convex current subproblem and a non-convex geometric update. Simulations demonstrate that the approach significantly suppresses sidelobes in single-beam superdirective beamforming and consistently enhances weighted sum rates in multi-user scenarios, outperforming fixed-grid and random fluid antenna baselines.

Abstract

Fluid antenna arrays (FAAs) offer a promising means of exploiting spatial degrees of freedom through adaptive port positioning. However, most existing communication models treat antenna ports as independent channel samples and therefore overlook the electromagnetic coupling that fundamentally governs compact apertures. This paper develops an electromagnetic-aware current-domain framework for planar FAAs. The proposed model integrates position-dependent multiport impedance, mutual coupling, radiated and accepted power, source-voltage feasibility, and channel variations into a unified baseband-compatible description. The framework is implementation-agnostic: the closed-form half-wave-dipole model adopted in this paper is only one instance and can be replaced by full-wave, measured, or surrogate impedance and embedded-pattern models. Building on this framework, we formulate two optimization-oriented design problems. The first addresses single-beam superdirective beamforming through the joint optimization of port currents and positions under sidelobe, current, voltage, and geometry constraints. The second maximizes the multi-user weighted sum rate via current-domain precoding and position optimization under accepted-power, current, voltage, and spacing constraints. In both cases, the electromagnetic model is not applied as an after-design correction, but is incorporated directly into tractable alternating algorithms with convex current or precoding subproblems and reduced-gradient geometry updates. Simulation results demonstrate that, when properly modeled, mutual coupling can be exploited as a valuable design resource, enabling lower sidelobes and persistent sum-rate gains over fixed-grid and random fluid-antenna benchmarks.

Problem

• fluid antenna array
• electromagnetic coupling
• mutual coupling
• compact aperture
• spatial degrees of freedom

Innovation

• fluid antenna array
• electromagnetic-aware modeling
• mutual coupling exploitation
• current-domain optimization
• superdirective beamforming