Reducing Nonlinear Errors in Wearable Biomagnetic Measurements Enabled by SERF Atomic Magnetometers Through Real-Time Suppression of Triaxial DC Interferences

Aiming at the issue of substantial nonlinear error arising from triaxial dc magnetic field interferences in wearable and mobile measurement scenarios, a triaxial magnetic field response model of single-beam atomic spin-exchange relaxation-free (SERF) magnetometer under nonzero magnetic condition is established, revealing that the effect of triaxial dc magnetic field interferences on the detected ac responses exhibits the nonlinear feature, while their impact on the dc response manifests as the interval-linear characteristic. Consequently, a closed-loop (CL) control system for mixed ac and dc magnetic fields is proposed. By leveraging the dc response within the feedback signal, a localized linearization control strategy is implemented across the triaxial magnetic fields, enabling direct and real-time suppression of dc interferences, and subsequently reducing their nonlinear impact on the measured ac response. Among them, the nonlinear impact caused by x-axis dc magnetic field interference decreases from 48.12% in the open-loop (OL) configuration to 0.01%. Additionally, it takes less time to suppress the interferences to below 2%, shortened from 4.7 s to 32 ms.