Identification of metallic mines using low-frequency magnetic fields

This paper addresses the issue of identifying conduction objects based on their response to low frequency magnetic fields -- an area of research referred to by some as magnetic singularity identification (MSI). Real time identification was carried out on several simple geometries. The low frequency transfer function of these objects was measured for both cardinal and arbitrary orientations of the magnetic field with respect to the planes of symmetry of the objects (i.e., different polarizations). Distinct negative real axis poles (singularities) associated with each object form the basis for our real-time identification algorithm. Recognizing this identification problem as one of inference form incomplete information, application of Bayes theorem leads to a generalized likelihood ratio test (GLRT) as a solution to the M-ary hypothesis testing problem of interest here. Best performance, measured through Monte Carlo simulation presented in terms of percent correct identification versus signal-to- noise ratio, was obtained with a single pole per object orientation.