Orthogonal Fluxgate Employing Digital Selective Bandpass Sampling

Abstract

Orthogonal fluxgate employing digital selective band pass sampling is developed and tested. The fluxgate output is sampled only once, at a single time instance during a number <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> of excitation cycles. This provides reconstruction of a measured magnetic field with a finite bandwidth from dc to 1/2 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> Hz. The sampling time instances correspond to the minimum magnitude of the fluxgate equivalent magnetic noise within the excitation cycles. As a result, the fluxgate resolution is improved by 40% compared to that obtained by conventional methods, where the fluxgate output is sampled a number of times and then averaged over each excitation cycle. The proposed approach not only improves the fluxgate equivalent magnetic noise, but also simplifies the fluxgate output processing by eliminating the need for analog synchronous detection.