Optimized design of cubic grid coil system with high space utilization ratio for weak biomagnetic signal measurement

The uniform field coils with large uniform region are important for improving the resolution in bio-magnetic signal measurements. The traditional coil design methods suffer from small space utilization ratio which limits the mobility and accuracy of bio-magnetic signal measurements. In this paper, a novel cubic grid coil (CGC) design method is presented, with significantly improved space utilization ratio and simple structure. The iterative fastest current drop method (IFCD) is proposed to simplify coil structure, thus ensuring the controllability of the cubic grid coil system. The superiority of CGCs has been demonstrated by finite element simulations and a series of experiments. The space utilization ratio of CGCs reaches 22.4% while maintaining 2% inhomogeneity, improved by about 6 times compared with traditional coils. Furthermore, the CGC-based system for directly eliminating the geomagnetic field achieves a low residual magnetic field noise of 29.7 pT/Hz/^1/2 at 1 Hz. The CGCs can provide new ideas for high-resolution, lightweight mobile measurements of weak bio-magnetic signals in the human body.