A high-sensitivity frequency counter for free-induction-decay signals
Abstract
Real-time frequency readout of time-dependent pulsed signals with a high sensitivity are key elements in many applications using atomic devices, such as FID atomic magnetometers. In this paper, we propose a frequency measurement algorithm based on the Hilbert transform and implement such a scheme in a FPGA-based frequency counter. By testing pulsed exponential-decay oscillation signals in the frequency range of 10 to 500 kHz, this frequency counter shows a frequency sensitivity better than 0.1 mHz/Hz^(1/2) at 10 Hz, with an output rate of 200 Hz. When the output rate is increased to 1000 Hz, the sensitivity remains better than 0.4 mHz/Hz^(1/2) at 10 Hz. The performance on frequency sensitivity is comparable with results obtained by off-line nonlinear fitting processes. In addition, this frequency counter does not require the pre-knowledge of the analytic expression of the input signals. The realization of such a device paves the way for practical applications of highly-sensitive FID atomic magnetometers.
Cite
@article{arxiv.2506.04780,
title = {A high-sensitivity frequency counter for free-induction-decay signals},
author = {Tong Gong and Ming-Rui Shu and Jiang He and Kai Liu and Yi-Ren Li and Xin-Jun Hao and Dong Sheng and Yu-Ming Wang and Yu-Kun Feng},
journal= {arXiv preprint arXiv:2506.04780},
year = {2025}
}
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