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In this Note, a new compressed sensing-based tuning algorithm has been developed to boost the sensor tuning performance of the proton precession magnetometers (PPMs). An end-to-end framework for the PPM's sensing free induction decay (FID) signal resonance based on orthogonal matching pursuit compressed sensing (OMPCS), dubbed OMPCS-FID resonance (OMPCS-FIDR), is developed and its working principle and implemented strategy are elaborated. By comparing the new sensor tuning approach with the state-of-the-art algorithms, i.e., peak detection, auto-correction, and secondary tuning, the results demonstrate that the proposed tuning method not only retains the performance but also overcomes the drawbacks of the state-of-the-art methods, which accelerates the possibilities of the PPM working in a scenario with a strong gradient magnetic field. [ABSTRACT FROM AUTHOR]

The sensor tuning of a proton precession magnetometer determines the signal-to-noise ratio (SNR) of induced free induction decay (FID) signal, while the quality of the FID influences the measurement accuracy of the geomagnetic field. Even though numerous methods have been proven to be effective in improving the tuning precision, how to efficiently decrease tuning error in a noisy environment is still a crucial challenge. To end this, a new tuning algorithm based on the combination of principal component analysis (PCA) and singular value decomposition (SVD), namely C-PCASVD, was presented in this paper. This novel algorithm aims to suppress the interference of the FID signal. The proposed C-PCASVD can obtain the dominant principal components of FID and noise, respectively. In addition, it is able to identify the corresponding singular values of interference, which could achieve an optimum trade-off between the denoised FID and noise reduction efficiency. The performance of the proposed method is tested on synthetic and field signals from different surveys. Good tuning frequency estimations are obtained at different SNRs. Through comparing the proposed C-PCASVD tuning algorithm with the state-of-the-art methods, including peak detection (PD), auto-correction and FFT (AC-FFT), and secondary tuning based on SVD (ST-SVD), the experimental results demonstrate that the C-PCASVD can significantly improve the tuning precision of proton precession magnetometer in a noisy environment. [ABSTRACT FROM AUTHOR]

Proton precession magnetometer (PPM) is a potential device to measure the low-frequency geomagnetic field in the time domain. Nevertheless, the uncontrollable noise such as power frequency noise, random noise, etc., severely affects the detection results. In this paper, aimed to boost the performance of the PPM, a novel real-time processing algorithm for the optimization of PPM output strategy based on the low-rank constraint (LRC) is proposed, and a new efficient framework, dubbed LRC-based geomagnetic data readout optimizer (LRC-GDRO), is implemented. This method aims to extract the dominant principal components of the pure magnetic signal and identify the singular values of noise. Thereby, the relative ideal signal without external noise, which still contains the ambient field information is yielded. Moreover, we develop a prototype device and compare the test results before and after using the proposed method. Consequently, compared with traditional PPM, the performance of the PPM using the proposed method has been significantly improved with a measurement accuracy of ± 0.2 nT. Furthermore, the experimental results reveal that the LRC-optimized PPM is comparable to a very high-accuracy Overhauser magnetometer in terms of 12 h geomagnetic field observation. [ABSTRACT FROM AUTHOR]

Resonant cavity is an important component of Overhauser magnetometer sensor. Its function is to make the working substance generate dynamic nuclear polarization effect in the sensor. An alternative design of resonant cavity based on the birdcage coil structure is proposed to make the resonant frequency in accordance with the polarization frequency of the working substance. The structure and equivalent circuit of resonant cavity are analyzed. The model of resonant cavity is established, and S-parameter is calculated. The simulating results show that resonant frequency of the resonant cavity is about 60 MHz, which is consistent with the polarization frequency of the working substance in the sensor, and Q-factor of the resonant cavity is about 90. A dual-coil structure for pick-up coil and series resonant circuit are designed for reducing interference. In addition, output signal experiment and simultaneous comparison testing of sensor prototype are conducted. Overall, this design has the advantages of high performance and strong anti-interference. The resolution, uncertainty, and range of the sensor reach to 0.005 nT, 0.2 nT, and 20 000–100 000 nT, respectively. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]