Angle-of-Arrival (AoA) estimation is an important problem in passive radio-frequency identification (RFID) systems. Affixing an RFID tag array to an object enables to acquire its orientation information. However, the electromagnetic interaction between the tags can induce mutual coupling interference, distorting the RFID fingerprint measurements used for AoA estimation. Moreover, RFID reader modes with radio-frequency (RF) noise-tolerant Miller encoding can induce $\pi $ -radians phase jump. In this article, we propose a scheme called RF-Mirror that can resolve the mutual coupling and phase jump problems and achieve accurate AoA estimation for an array with two or more tags. First, we characterize the impact of mutual coupling on a tag’s signal fingerprint and develop novel RSSI/phase-distance models. We then develop new experimental methods and signal processing techniques to verify the effectiveness of the proposed models. Based on the validated models, we develop new AoA estimation algorithms for tag arrays that deal with the mutual coupling effect explicitly. We provide extensive experimental results, which demonstrate that RF-Mirror can achieve significantly improved performance compared to baseline schemes, with median AoA estimation errors of 11.65° and 6.29° for two- and four-tag arrays, respectively.

中文翻译：

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具有相互耦合的 RFID 标签阵列的准确 AoA 估计

到达角（AoA）估计是无源射频识别（RFID）系统中的一个重要问题。将 RFID 标签阵列粘贴到对象上可以获取其方向信息。然而，标签之间的电磁相互作用会引起相互耦合干扰，从而扭曲用于 AoA 估计的 RFID 指纹测量。此外，具有射频 (RF) 容噪米勒编码的 RFID 阅读器模式可以诱导 $\pi $-弧度相位跳跃。在本文中，我们提出了一种称为 RF-Mirror 的方案，该方案可以解决互耦合和相位跳跃问题，并为具有两个或多个标签的阵列实现准确的 AoA 估计。首先，我们描述了相互耦合对标签信号指纹的影响，并开发了新的 RSSI/相位距离模型。然后，我们开发新的实验方法和信号处理技术来验证所提出模型的有效性。基于经过验证的模型，我们为标签阵列开发了新的 AoA 估计算法，以明确处理相互耦合效应。我们提供了广泛的实验结果，表明 RF-Mirror 与基线方案相比可以显着提高性能，两个和四个标签阵列的中值 AoA 估计误差分别为 11.65° 和 6.29°。