Loop Array Antenna in a Borehole for Directivity to a Horizontally Polarized Wave
Loop Array Antenna in a Borehole for Directivity to a Horizontally Polarized Wave
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DOI：
10.1109/tgrs.2022.3177444
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发表时间：
2022
影响因子：
8.2
通讯作者：
S. Ebihara;Masayuki Matsumoto
中科院分区：
文献类型：
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作者：
S. Ebihara;Masayuki Matsumoto
提出了一种用于钻孔雷达的定向天线，该天线利用垂直钻孔中的水平极化波。该天线是几个水平环形天线的阵列，垂直排列。当平面波入射到天线上时，阵列单元的到达时间的差异使我们能够估计到达方向(DOA)。我们给出了一个简单的表示到达时间差的模型，并提出了一种DOA估计算法。在此基础上，利用矩量法对阵列信号进行了电磁场分析，合成了阵列信号，并将该算法应用于阵列信号。我们发现天线单元之间的互耦合会影响DOA估计，并且天线单元之间大约3 cm的间距阻止了互耦合。利用矩量法对天线的跨孔测量进行了仿真，验证了天线的性能。我们在潮湿的土壤中进行了现场实验，以检验天线的性能。所提出的充水井眼环形阵列天线从另一个井眼的信号源接收到直达波。将该算法应用到实际测量数据中，可以在方位角误差小于15°、仰角误差小于10°的情况下对信源进行波达方向估计。
We propose a directive antenna for borehole radar, using a horizontally polarized wave in a vertical borehole. This antenna is an array of several horizontal loop antennas, arranged vertically. When a plane wave is incident on the antenna, the differences in arrival times at the array elements enables us to estimate the direction of arrival (DOA). We present a simple model representing the arrival time difference and propose an algorithm for DOA estimation. Further, we synthesized the array signal by analyzing the electromagnetic field using the method of moments (MoM) and applied the proposed algorithm to the signal. We found that mutual coupling between antenna elements affects DOA estimation, and that a space of about 3 cm between antenna elements prevents mutual coupling. Using the MoM analysis, we simulated a cross-hole measurement to demonstrate the antenna’s ability. We carried out field experiments in wet soil to examine the antenna’s ability. The proposed loop array antenna in a water-filled borehole received a direct wave from a source in another borehole. After applying the proposed algorithm to the measured data, we found that we could estimate the DOAs to the source with an error of less than 15° in the azimuth angle and 10° in the elevation angle.