Design of Uniform Magnetic Field Coils With Array Characteristics Under Asymmetric Coupling Effect in Magnetocardiography Devices

Uniform magnetic field coils (UMFCs) are vital for generating a magnetic field environment that meets the magnetocardiography (MCG) measurement requirements. However, designing UMFCs under the influence of asymmetric coupling within a single-ended magnetic shielding cylinder (SEMSC) is challenging. To address this issue, this article proposes a design method for a coil with array characteristics (CAC), in which the current of each coil unit (CU) is adaptively adjusted based on the coupling differences, thereby enabling the CAC to generate a highly uniform magnetic field within the SEMSC. First, an analytical model of the array within the SEMSC is established. Subsequently, a two-stage particle swarm optimization (TS-PSO) algorithm is proposed to optimize the currents and turns of each CU, and the CAC path is planned based on a depth-first search (DFS) strategy. Simulation and experimental results demonstrate that the CAC achieves superior magnetic field uniformity within the SEMSC compared to other coils. Furthermore, magnetic field compensation experiments validate the effectiveness of CAC in improving MCG measurement quality, indicating that the average power spectral density (PSD) of magnetic field noise in the 1-40Hz frequency range is reduced from 52.34 to 26.16 fT/ ${\mathrm {Hz}}^{\mathrm {1/2}}$ . These results highlight the significant importance of this method in creating the magnetic environment for MCG measurements.