Weak magnetic anomaly signal detection based on the entropy of mixed differential signal

Z Wang,Q Xu,J Qiu,D Xie,J Ou

doi:10.1063/9.0000080

Abstract

Magnetic anomaly detection is of great significance in geological exploration and underwater target detection. However, the magnetic anomaly signal is not easy to be detected because of its weakness relative to the magnetic environmental noise, and the detection probability of the magnetic anomaly signal is affected by signal frequency. We propose a mixed differential minimum entropy method which can detect the weak magnetic anomaly signal. The proposed method combines the coherence difference method with the synchronous reference subtraction method in preprocess, which can suppress common-mode noise in the signal and relax the limitation of the frequency of the magnetic anomaly signal on the detection ability. Using the concept of entropy to describe the preprocessed signal can eliminate the residual high-frequency noise and further improve the signal-to-noise ratio of the target signal. Results show that the proposed method may effectively improve the signal-to-noise ratio and increase the frequency range of the magnetic anomaly signal, which has better detection performance than that of traditional method.

Highlights

With the rapid development of magnetometer, the research on magnetic anomaly detection (MAD) technology of the underwater target has been further developed in recent years.[1,2,3] MAD is widely utilized for the search, localization, and identification of the ferromagnetic targets.[4,5,6] Usually, when the detection range is about three times the size of the ferromagnetic target, the magnetic anomaly of the target is equivalent to the magnetic field distribution of a single magnetic dipole to simplify the model and calculation reasonably.[7]
To effectively detect the weak magnetic anomaly signal produced by the ferromagnetic target in complex background noise, it is necessary to suppress the influence of noise on magnetic anomaly signal as far as possible assuming the information of the ferromagnetic target is retained
We find that the magnetic anomaly signal between two synchronously detected data will not be eliminated because the synchronous reference subtraction (SRS) method does not involve the calculation of eliminating amplitude difference by using coherence in the frequency domain

Summary

INTRODUCTION

With the rapid development of magnetometer, the research on magnetic anomaly detection (MAD) technology of the underwater target has been further developed in recent years.[1,2,3] MAD is widely utilized for the search, localization, and identification of the ferromagnetic targets.[4,5,6] Usually, when the detection range is about three times the size of the ferromagnetic target, the magnetic anomaly of the target is equivalent to the magnetic field distribution of a single magnetic dipole to simplify the model and calculation reasonably.[7] A representative method is the orthogonal basis function (OBF) method, which is to project the magnetic anomaly signal of the magnetic dipole model into the three-dimensional orthogonal basis and to detect the abnormal state by calculating the energy of the coefficient.[8] The OBF method is a classical MAD method based on a single magnetic dipole model It can effectively detect magnetic anomaly signal in the white Gaussian noise environment. The proposed method can effectively improve the detection ability of weak magnetic anomaly signal of underwater targets

MODEL DESCRIPTION

EXPERIMENTAL

CONCLUSIONS