Proposal and theoretical evaluation of the active shield with self-tunable loop current array

An active shielding module consisting of self-tunable loop current array is proposed. Loop currents in the array are independently controlled by the magnetometer dedicated to each of them. Since magnetic field decays as 1/r³ along the distance r, the magnetic noise should be overcompensated at the location of the loop current array to provide a good cancellation in the shielded area. In order to enable overcompensation in a stable feedback system, a small additional loop is combined to the magnetometer that reduces magnetic direct coupling from the main loop current to the magnetometer. Shielding performance of an array consisting of 25 (5 by 5) loop currents is evaluated numerically on the 4 m by 4 m evaluation plane for the magnetic dipole disturbance source placed 3-4 m beyond the array. Attenuation of magnetic field is calculated as 1/15-1/5 over the evaluation plane.