A high-accuracy and non-intermittent frequency measurement method for Larmor signal of optically pumped cesium magnetometer

Abstract

The optically pumped cesium magnetometer is a quantum magnetometer based on the Zeeman effect. The frequency of the output Larmor signal is proportional to the magnetic field intensity. Therefore, improving the measurement accuracy of the Larmor frequency can make the magnetic field measurement more accurate. However, the Larmor signal is easily coupled with various randomly distributed noises, which will generate an unavoidable trigger error. To address the above problem, we propose a multi-gate and equal-precision fusion method. In this method, the trigger error is averaged into the count of each small gate through the multi-gate structure to improve the frequency measurement accuracy and the continuous sampling performance. We implemented this method on the FPGA and conducted indoor and outdoor experiments. The experimental results show that this method not only improves the measurement accuracy by three times of the traditional method, but also enhances the stability and noise suppression ability of the system, and can provide technical and instrumental support for magnetic field measurement projects.