Frequency Characteristics Analysis for Magnetic Anomaly Detection

This letter presents a frequency characteristics analysis for a magnetic anomaly detection (MAD) study. A magnetic dipole model is developed to study the energy distribution of the obtained MAD signal in the frequency domain, where fh is proposed to define the signal high-frequency boundary. The relations between fh and other parameters, such as the velocity of the target (or platform), closest path approach (CPA), magnetic moment strength, magnetic moment orientation (MMO), and sensor orientation, are analyzed. We find that the frequency response is independent of the moment strength. The combined effects of the MMO and sensor orientation on fh are defined by the functio n g(alpha , beta , theta , phi ), which is studied by the Monte Carlo method, yielding a maximum value of max(g) approximate to 0.85. Thus, the function fh = 0.85v/CPA is advanced for frequency boundary estimation. The proposed theoretical analysis is examined in an experiment to aid in extracting the magnetic anomaly signal effectively.