Full-Frequency Range Cross-Axis Decoupling for Dual-Axis SERF Magnetometer Based on Amplitude-Phase Characteristics

Compared to single-axis measurement, multiaxis spin-exchange relaxation-free (SERF) atomic magnetometer has shown its superiorities in biomagnetic measurement recently. However, in multiaxis measurement, cross-axis coupling error can introduce undesired output in the response signals, which vary with frequency and will have an adverse effect on measurement accuracy. To effectively suppress this error, we propose a full-frequency range dual-axis cross-axis decoupling method based on amplitude-phase characteristics for dual-beam magnetometer. We analyze and measure the cross-axis coupling effect under different residual magnetic fields along the z-axis, and demonstrated that the residual magnetic field along the z-axis has great impact on the cross-axis coupling. Although the cross-axis coupling can be minimized by adjusting the residual magnetic field along the z-axis to zero, the cross-axis coupling still remains. Therefore, we establish the input-output equation in matrix form and derive the complex transform matrix based on amplitude-phase characteristics. Then we utilize the corresponding solving matrix to calculate the decoupling measurement results from the response signals under different cases of magnetic fields. Our method can realize a dual-axis complete decoupling measurement within full-frequency range and provides a comprehensive description of the magnetic fields to be measured, including amplitude and phase information. The validity and effectiveness of our decoupling method is verified, and it is demonstrated that our method can markedly enhance the measurement accuracy. We can realize the measurement error of the magnetic field phase difference lower than 1°, the relative measurement error of the magnetic field amplitude along the x-axis lower than 0.23% and that along the y-axis lower than 0.02%. Moreover, this method can be extended to any linear multiaxis measurement system.