Dipole detection and localization processing

Abstract

Dipole detection and localization systems and methods employing improved processing techniques. The first processing technique provides for higher spatial resolution by implementing maximum likelihood beamforming processing to detect and locate a dipole in a manner analogous to the processing of wave propagation phenomena. The high resolution technique is comprised of using data derived from an array of magnetic sensors that is arranged in the form of a vector of coefficients in lieu of a matrix. This vector can be either the magnetic field components or the Anderson function expansion coefficients and is used to form a dyadic matrix, to which a multiple of an identity matrix is added to prevent singularity. The second improvement uses more than three Anderson function expansions to achieve detection and localization of the dipole. The use of more than three Anderson functions more effectively normalizes the noise dependence by providing better noise representations, and provides for detection and localization of multipoles. The third improvement provides for multiple-pass multiple-target processing of data measured by the array of sensors. First, the location of the largest dipole in the field-space of the array is determined, and its moment and orientation are determined. The field due to a dipole at that location and orientation is then removed from the measurement data and the process is repeated. The field is removed by subtracting out its contribution at each of the sensors in the array, and then estimating the location of the next largest dipole. Simulations have shown that this process provides the ability to resolve multiple dipoles, when applied as many times as is needed.