A DSP-Based Magnetic Compensation System for Optically Pumped Magnetometer

Traditional active magnetic compensation systems applied to magnetocardiography (MCG) suffer from low compensation accuracy and high structural complexity. To further suppress the residual magnetic field and improve the integration degree of the compensation system, an active magnetic compensation system based on a digital signal processor (DSP) and an active disturbance rejection controller (ADRC) is proposed in this article. In this system, a cylindrical coil driven by the DSP is utilized to generate a compensation field. After introducing the ADRC, the cylindrical coil receives a dynamic compensation current, and the residual magnetic field monitored by a reference optically pumped magnetometer (OPM) changes significantly, which is manifested as a magnetic compensation signal of high precision generated in the predetermined target area. The experimental results show that the system suppresses the dc component and fluctuation of the residual magnetic field to 0 and 4 pT. It improves the noise suppression ratio (NSR) to more than 6.5 times in the low frequency range from 1 to 50 Hz, which indicates that the compensation system has great suppression performance.