A High-Precision Frequency Measurement Algorithm for FID Signal of Proton Magnetometer

摘要

The accuracy of measuring a magnetic field using a proton magnetometer depends on the accuracy of frequency measurement of the free induction decay (FID) signal generated by the proton magnetometer. Increasing the accuracy of frequency measurement could increase the accuracy of measuring magnetic fields. In this paper, we propose a multichannel frequency measurement to improve the accuracy after analyzing the error sources of existing frequency measurements based on the FID signal. In addition, we describe the basic principle of the proposed method and the formula for the calculation of the measured FID signal frequency and error in detail. Moreover, we implement a prototype device using the multichannel frequency measurement and compare the test results before and after using the proposed method. Finally, the indoor and outdoor experimental data in the case of using the prototype device are compared with those in the case of a very high-precision overhauser magnetometer. The comparisons indicate that the proposed method improves the accuracy of the FID signal frequency measurement, and therefore, improves the accuracy of magnetic field measurement.