Movable antenna (MA) systems have emerged as a promising technology for future wireless communication systems. The movement of antennas gives rise to mutual coupling (MC) effects, which have been previously ignored and can be exploited to enhance the capacity of multiple-input multiple-output (MIMO) systems. To this end, we first model an MA-enabled point-to-point MIMO communication system with MC effects using a circuit-theoretic framework. The capacity maximization problem is then formulated as a non-concave optimization problem and solved via a block coordinate ascent (BCA)-based algorithm. The subproblem of optimizing MA positions is challenging due to the presence of the analytically intractable MC matrices. To overcome this difficulty, we develop a trust region method (TRM)-based algorithm to optimize MA positions, wherein Sylvester equations are employed to compute the derivatives of the inverse square roots of the MC matrices. Simulation results show significant capacity gains from leveraging MC effects, primarily due to customizable MC matrices and superdirectivity.

翻译：可移动天线系统已成为未来无线通信系统中一项前景广阔的技术。天线的移动会引发互耦效应，这一效应先前被忽视，但可被用于提升多输入多输出系统的容量。为此，我们首先基于电路理论框架，对考虑互耦效应的可移动天线点对点MIMO通信系统进行建模。随后，将容量最大化问题表述为一个非凹优化问题，并通过基于块坐标上升的算法进行求解。由于存在解析上难以处理的互耦矩阵，优化天线位置的子问题具有挑战性。为克服此困难，我们开发了一种基于信赖域方法的算法来优化天线位置，其中采用西尔维斯特方程来计算互耦矩阵逆平方根的导数。仿真结果表明，利用互耦效应可带来显著的容量增益，这主要归功于可定制的互耦矩阵和超方向性。