Reconfigurable antenna systems (RASs), such as fluid antennas and movable antennas, are poised to play a pivotal role in sixth-generation (6G) systems by dynamically adapting the antenna elements for system performance enhancement. However, unlocking their full potential requires channel models that accurately capture the influence of antenna configurations on the radiation, propagation, and reception of signals. Existing channel models suffer from several limitations, such as neglecting polarization effects, being restricted to specific antenna types, or relying on oversimplified assumptions. In this paper, we propose a general electromagnetic (EM)-based channel model grounded in spherical vector wave expansion (SVWE). The proposed EM-based channel model captures the impact of antenna position and orientation on the channel gain, thereby making it particularly well-suited for RASs. The effectiveness and accuracy are validated through comparisons with commercial simulation software, demonstrating excellent agreement in predicted channel gains. Moreover, it is shown that antenna orientation is a critical factor governing communication performance, and that dynamically adjusting the antenna orientation yields up to 70% improvement in achievable communication rate compared to a fixed-antenna configuration.

翻译：可重构天线系统（RAS），例如液态天线和可动天线，通过动态调整天线单元以增强系统性能，有望在第六代（6G）通信系统中发挥关键作用。然而，若要充分发挥其潜力，需要能够精确刻画天线配置对信号辐射、传播与接收影响的信道模型。现有信道模型存在若干不足，例如忽略极化效应、局限于特定天线类型或依赖过度简化的假设。本文提出一种基于电磁（EM）理论的通用信道模型，其理论基础为球面矢量波展开（SVWE）。该电磁信道模型能够精确捕捉天线位置与朝向对信道增益的影响，因而特别适用于可重构天线系统。通过与商业仿真软件的对比验证，本模型在预测信道增益方面展现出极佳的一致性，证明了其有效性与精确性。此外，研究表明天线朝向是决定通信性能的关键因素，与固定天线配置相比，动态调整天线朝向可使可达通信速率提升最高达70%。