Synchronous RF Pulse Regulation and Adaptive Filtering Measurement Method for Free-Induction-Decay Magnetometers

High-sensitivity magnetic field measurement over a large dynamic range is crucial for geomagnetic applications. Free-induction-decay (FID) magnetometers are capable of operating in unshielded environments with excellent performance, demonstrating their potential for geomagnetic field applications. In this study, we propose a novel synchronous RF pulse regulation and adaptive filtering measurement method for FID magnetometers to enhance their performance. Benefiting from synchronous RF pulse regulation, the magnetometer achieves real-time, high-precision measurements across a large dynamic range covering typical geomagnetic fields. Meanwhile, adaptive filtering effectively improves the signal-to-noise ratio (SNR), leading to a fivefold sensitivity enhancement—from 15.37 to $3.12~ \text {pT}/{(\text {Hz})}^{1/2} $ , with an equivalent instrument sensitivity (EIS) of $0.47~ \text {pT}/{(\text {Hz})}^{1/2} $ . Finally, the application capability in geomagnetic environments is validated through tests in an unshielded environment. This study provides a significant advancement in enhancing FID magnetometer performance and expanding their practical applications in geomagnetic environments.