2026 Iacovelli Movable Fluid Antenna Circuit Field Model

Movable and fluid antenna systems turn antenna position into a design variable. At sub-wavelength spacing, however, their behavior is governed by mutual coupling, modeled by two disjoint traditions: circuit-theoretic impedance matrices and field-theoretic kernels. This paper unifies the two methodologies. Starting from the impedance kernel of a holographic surface, the authors identify its resistive part with ohmic plus radiated power and its reactive part with stored-energy imbalance, establishing a circuit-field equivalence that relates the multiport impedance matrix to the kernel. The resulting formulation in the wavenumber domain shows how the resistive kernel asymptotically diagonalizes, distinguishing between modes that radiate and those that only dissipate. The study proposes a coupling-aware multi-user sum-rate maximization strategy under specific constraints, utilizing weighted-MMSE and projected-gradient methods. Additionally, findings reveal conditions under which coupling either negatively or positively impacts performance through the analysis of a half-wavelength corollary and superdirectivity margin. Overall, this work advances the design of fluid and movable antenna systems by integrating circuit and field approaches to optimize performance.