Compact high-frequency (HF) antenna arrays are convenient to deploy. However, using a small-aperture HF surface wave radar for wind direction measurement is still a challenging problem, since an unsatisfactory array pattern degrades the performance of Bragg ratio estimation. To address this issue, a digital beamforming method based on a superdirective synthesis technique for an HF receiving array that consists of seven elements positioned on a 5-m diameter circle is proposed. This superdirective beamforming method contains a sidelobe constraint. Subsequently, a hybrid superdirective beamforming and direction-finding method is adopted to estimate the wind direction using a multifrequency HF radar based on a circular array (MHF-C). The superdirective beamforming approach, as well as the wind direction estimation method, is presented in detail. The wind direction estimation method has been applied to the raw data sets that were collected with two MHF-C radars installed along the coast of the East China Sea in April 2015 and comparisons between radar-derived and in situ wind directions have been made. Ship-mounted anemometers were used to obtain in situ measurements at six sampling locations within the overlapping coverage of both radars. Another comparison between the radar-derived and anemometer-derived wind directions, which were obtained from June 15, 2015 to August 12, 2015, has also been made. The results indicate that the proposed method is effective for wind direction estimation with root-mean-square differences (RMSDs) between 24.1° and 33.1°, when wind speeds were higher than 5 m/s. The analysis encourages us to recommend a minimum wind speed of 5 m/s for reasonably assessing wind direction measurement performance.

中文翻译：

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基于圆阵的小口径高频雷达风向估计

紧凑的高频 (HF) 天线阵列便于部署。然而，使用小口径 HF 表面波雷达进行风向测量仍然是一个具有挑战性的问题，因为不令人满意的阵列模式会降低布拉格比估计的性能。为了解决这个问题，提出了一种基于超指向合成技术的数字波束成形方法，用于由位于 5 米直径圆上的七个元件组成的 HF 接收阵列。这种超指向波束成形方法包含旁瓣约束。随后，采用混合超指向波束成形和测向方法，使用基于圆形阵列的多频高频雷达（MHF-C）估计风向。详细介绍了超指向波束成形方法以及风向估计方法。风向估计方法已应用于 2015 年 4 月在东海沿岸安装的两台 MHF-C 雷达收集的原始数据集，并对雷达衍生的风向和原位风向进行了比较。船载风速计用于在两个雷达重叠覆盖范围内的六个采样位置进行现场测量。还对 2015 年 6 月 15 日至 2015 年 8 月 12 日期间获得的雷达衍生风向和风速计衍生风向进行了比较。结果表明，当风速高于 5 m/s 时，所提出的方法对于均方根差（RMSD）在 24.1°和 33.1°之间的风向估计是有效的。