A Compact Seafloor Electromagnetic Receiver for Ship Electromagnetic Signature Measurement

The measurement of underwater target electromagnetic signatures is crucial for enhancing underwater information perception capabilities. Currently, common ship detection technologies include acoustic, laser, infrared, and electric- and magnetic-field detection. Compared with other technologies, electromagnetic detection offers superior signal stability and accurate positioning. However, current underwater electromagnetic receivers face several challenges, such as poor measurement accuracy, inability to simultaneously measure alternating and static magnetic fields, and low efficiency in maritime operations. This paper describes a compact seafloor electromagnetic receiver used for ship detection. It features a spherical structure with acoustic telemetry modem (ATM) circuits for device recovery and a signal-acquisition circuit connected to an Ag–AgCl electric-field sensor, induction coil, and fluxgate sensors. The device supports three-axis electric and six-channel magnetic field signal collection. Deployed for validation experiments in the northern Yellow Sea, it measured signals from artificial sources at various frequencies and performed spectral analysis of the time series, confirming the capture of corresponding electromagnetic signals and validating the effectiveness of the device. The background noise levels of the electric, alternating magnetic, and static magnetic fields were 0.1 nV/m/√<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Hz</i> at 1 Hz, 0.1 pT/√<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Hz</i> at 1 Hz, and 10 pT/√<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Hz</i> at 1 Hz, respectively. The device can operate underwater in a data acquisition state for 90 days at a depth of 1000 m with power consumption of 400 mW. It features the advantages of complete electromagnetic signal capture, low power consumption, and high efficiency in maritime operations, making it suitable for the electromagnetic detection of ships.