Direction of arrival (DOA) estimation is essential in building the wireless electromagnetic (EM) environment. However, the conventional DOA estimation methods have been criticized for their hardware complexity, high cost, and low energy efficiency. Recently, metasurface-based methods have emerged as promising alternatives that offer cost-effective solutions. Nevertheless, the existing studies have neglected angle sensitivity, an intrinsic physical property of metasurface, leading to errors in DOA estimations. To address this issue, we propose a generalized high-precision and wide-angle DOA estimation method based on space-time-coding digital metasurfaces (STCDM). By carefully designing two elementary STC sequences, we realize two angle-independent harmonic states to construct a specified orthogonal matrix. Then, the harmonics, modulated by each meta-column in accordance with the matrix, are sampled by a single channel receiver at different time intervals. Upon the reception of the signal, the information on the metasurface can be comprehensively retrieved through matrix operations, facilitating the high-accuracy DOA estimations using the Array Signal Processing (ASP) algorithms. This work focuses on eliminating the influence of angle sensitivity on metasurface-based DOA estimations, which guarantees high accuracy and substantially reduces hardware requirements. The proposed method holds potential for various applications, including the Internet of Things (IoT) and integrated sensing and communication (ISAC).

中文翻译：

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基于时空编码数字超表面的广义高精度广角DOA估计方法


到达方向 (DOA) 估计对于构建无线电磁 (EM) 环境至关重要。然而，传统的DOA估计方法因硬件复杂、成本高、能源效率低而受到批评。最近，基于超表面的方法已经成为有前途的替代方案，可以提供具有成本效益的解决方案。然而，现有研究忽略了超表面的固有物理特性——角度敏感性，导致DOA估计出现误差。为了解决这个问题，我们提出了一种基于时空编码数字超表面（STCDM）的广义高精度广角DOA估计方法。通过仔细设计两个基本的STC序列，我们实现了两个与角度无关的谐波状态来构造指定的正交矩阵。然后，由每个元列根据矩阵调制的谐波由单通道接收器以不同的时间间隔进行采样。接收到信号后，可以通过矩阵运算全面检索超表面信息，便于使用阵列信号处理（ASP）算法进行高精度DOA估计。这项工作的重点是消除角度灵敏度对基于超表面的 DOA 估计的影响，从而保证高精度并大幅降低硬件要求。所提出的方法具有多种应用的潜力，包括物联网（IoT）和集成传感与通信（ISAC）。