Receiving resonant phase-modulated signals using atomic magnetometer for magnetic communications

Telecommunication in harsh environments, such as an electrically conductive medium, requires the use of carrier bands with very-low and ultralow frequencies for radiofrequency links. Recent advancements in atomic magnetometers operating at very-low frequencies have facilitated the reception of digitally modulated signals. We demonstrate the ability to transmit and receive quadrature phase-shift keying (QPSK) signals using a multi-resonant loop antenna and atomic magnetometer. The introduced multi-resonant loop antenna noticeably enhances the bandwidth, with an expansion exceeding 70% compared with a single-loop antenna. Additionally, utilizing an atomic magnetometer, we successfully demodulated a QPSK signal with a carrier frequency of 20 kHz and a symbol rate of 150 symbols per second. The acquired measurements reveal an error vector magnitude of 7.29% and a signal-to-noise ratio of 30.9 dB. These findings highlight the potential of the proposed system for efficient and reliable very-low frequency telecommunication in challenging environmental conditions.