Electromagnetic anomaly identification algorithm based on signal fingerprinting
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摘要: 本文基于信号指纹技术，通过研究短时（<10 min）地磁异常数据识别算法，完成了对地磁干扰信号类型的识别。本文所用信号指纹技术结合了短时傅里叶变换、小波变换、信号二值化、文本相似性哈希等多种数据和文本处理方法，将一定时间内的波形数据转换为一个32位的整型数字，极大地压缩了信号的特征信息，因此在很大程度上减少了后续查找与分类过程中所需处理的数据。利用该算法对河北红山地磁台2016年5月1—3日两套GM4磁通门磁力仪的原始秒数据的计算结果表明，本文算法可以快速准确地识别干扰信号类型，为实现地磁相对观测数据中异常信号的自动提取提供技术支撑。Abstract: This paper makes research on recognition algorithm of short-time （<10 min） geomagnetic anomaly data, based on signal fingerprint, to recognize the categories of geomagnetic disturbance signals. The signal fingerprinting used in this study can convert the waveform data for a given period of time into a 32-bit integer, basing on the combination of multiple data and text-processing methods, such as Fourier transform, wavelet transform, signal binarization and MinHash, which greatly compresses the feature information of signals, thus greatly reduces the amount of data to be located and classified in the following research. The experiment uses raw second-scale data of two sets of GM4 fluxgate magnetometers recorded at Hongshan geomagnetic station (LYH) in Longyao city of Hebei Province from 1 to 3 May 2016, and the results indicate that the algorithm in this paper can quickly and accurately recognize categories of interference signals, and provides technical support for automatic abnormal signals extraction of geomagnetic relative record data.
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Keywords:
- short-period anomalies /
- signal fingerprinting /
- MinHash
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图 1 短时傅里叶变换所用波形数据（a）及其变换后的频谱图（b）
Figure 1. Waveform used in short-time Fourier transform （a） and the spectrogram after the transform （b）
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图 2 短时傅里叶变换局部放大图形。(a) 波形数据； (b) 频谱图
Figure 2. Partial amplification of short-time Fourier transform. (a) Waveforms; (b) Spectrogram
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图 3 对截取图像开始时刻作二维小波变换后的图像
Figure 3. Imagines of 2D wavelet transform of the partial images
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图 6 理论波形加噪声结果（最小信噪比为2.5）
Figure 6. Results of theoretical waveform with noise （minimum signal to noise ratio is 2.5）
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图 9 正弦图形计算结果
（a），（c）为选取最大的90个点；（b），（d）为选取最大的40个点
Figure 9. Calculation results of the sine images
（a） and （c） are the maximum selection of 90 points； （b） and （d） are the maximum selection of 40 points
表 1 指纹提取过程所用的参数
Table 1 Parameters used in fingerprinting extraction
原始数据采样率 1 Hz 短时变换时间窗 60点 短时变换时间窗延迟 10点 短时傅里叶变换重采样点数 32 二维小波变换时间窗 60点 二维小波变换时间窗延迟 6点 二维小波变换重采样点数 32 
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