Mutual-Coupling-Aware Electromagnetic and Signal Processing Co-Design for Pixel Antenna Arrays

Abstract

Reconfigurable pixel antenna arrays provide additional electromagnetic (EM) degrees of freedom for wireless transmission by enabling hardware-level adaptation of radiation responses. In practical arrays, inter-element mutual coupling (MC) alters the switch-state-dependent responses, causing MC-unaware designs to be mismatched with the realized coupled-array channels. To address this issue, we propose an MC-aware EM and signal-processing co-design framework for downlink multi-user multiple-input single-output (MU-MISO) systems. The full pixel antenna array is modeled as a unified multi-port circuit network that jointly characterizes the feed ports and switch-controlled pixel ports. By combining the impedance matrix extracted from Computer Simulation Technology (CST) Studio Suite simulations with the full-array open-circuit far-field responses, we construct a switch-state-dependent EM-domain channel that explicitly captures both intra-antenna pixel coupling and inter-element MC. Based on this model, we formulate a sum-rate maximization problem over the binary switch-state vector and the transmit precoder. To address the resulting mixed-integer non-convex problem, we develop an alternating optimization algorithm in which the binary switch-state vector is updated via sequential exhaustive block optimization (SEBO), while the transmit precoder is optimized using fractional programming (FP). CST-based simulations show that the proposed MC-aware design outperforms MC-unaware, MC-free, and conventional patch-array baselines. These results demonstrate that accurate MC modeling is essential not only for reducing model mismatch, but also for exploiting the coupled embedded responses of practical pixel antenna arrays.