Various embodiments of the present technology use low-frequency magnetic signals for communication and location applications. Compared to the case of traditionally used radio-frequency electromagnetic signals, their advantage in the presence of strong signal attenuation is in the extended spatial range. Some embodiments use an optically pumped atomic magnetometer operated as a sensor to achieve high detection sensitivity. The spatial range can be extended to hundreds of meters when noise is suppressed by the use of the available sensor sensitivity. In some embodiments, a one-channel spread-spectrum signal processing technique can be used to eliminate the systematic fluctuations coming from power grid (or another source) harmonics and reduce the ambient noise by averaging uncorrelated fluctuations from the environment.
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