Real-Time Disturbance Magnetic Field Observation Method Based on Multiple Sensors to Enhance the Directionality of Active Disturbance Suppression in MCG Systems

Active magnetic compensation is commonly combined with passive magnetic shielding structures in magnetocardiography (MCG) measurements to suppress environmental magnetic disturbances and improve the signal-to-noise ratio (SNR). Accurate measurement of the disturbance field in the target region is essential for control decisions. Active compensation systems that rely on a single reference sensor often suffer from inaccurate disturbance estimation and degradation of the target signal SNR. In this work, a computationally efficient magnetic field observation method based on 2-D spherical harmonics is proposed. By exploiting the spatial correlation differences of signals, a Kalman filter is designed to suppress random noise and target signal components in the reference sensor while interpolating the disturbance field in the target region. Validation experiments were conducted on a prototype MCG system equipped with a barrel-shaped magnetic shielding structure. The results demonstrate that the proposed observation method can effectively guide the active compensation system to suppress disturbances in the target region, with the suppression rate improved from 43.05% using a single sensor to 84.14%. This disturbance observation approach provides valuable insights for the development of multichannel active compensation systems and MCG devices operating without passive magnetic shielding.