## 1 Introduction  
With the increasing attention paid by countries around the world to marine resources, how to further develop and explore marine resources has become a research hotspot. At the same time, with the rapid development of various underwater equipment, such as UUVs (unmanned underwater vehicles), AUVs (autonomous underwater vehicles), underwater buoy systems, underwater biomimetic robots, and underwater unpowered/powered gliders, underwater target detection methods are gradually improving, and the focus of marine science and technology research is gradually shifting to underwater target detection. As a traditional underwater detection method, acoustic detection is widely used in various types of underwater target detection due to its advantages, such as slow underwater attenuation, long detection distance, and the ability to detect small targets. However, acoustic detection also has problems, such as being greatly affected by ocean background noise and being easily exposed by active acoustic detection. With the rapid development of seismic and noise reduction technology in various countries around the world, underwater acoustic detection technology is further limited, appearing inadequate in complex marine environments and adversarial fields. In recent years, countries around the world have vigorously developed underwater non-acoustic detection technology, studying the electric field, magnetic field, and gravity field of underwater targets. The underwater electric field is an important physical field for ships. According to the signal frequency band, the electric field is mainly divided into a steady-state electric field (mainly including a corrosion-related static electric field) and an alternating electric field (mainly including a shaft frequency and power frequency electric field). Among them, the shaft frequency electric field signal generated by the rotation of the propeller is often used for long-distance detection of underwater targets due to its strong ability to resist natural interference, obvious near-field characteristics, and line spectrum characteristics of the power spectrum. The static electric field signal generated by corrosion and anti-corrosion currents is easy to track and locate due to its obvious near-field characteristics and high signal-to-noise ratio. Therefore, it is often used for end positioning of positioning systems, mine electric field fuses, and underwater array detection [1; 2; 3; 4; 5]. In recent years, attention has been widely paid to electric field detection. Many achievements have been made in electric field detection, in such aspects as theoretical modeling, detection and identification, and tracking and localization of underwater objects with an electric field. The electric field of an underwater object has been widely used in the methods used to detect objects [6; 7; 8; 9; 10; 11; 12]. Unlike a corrosion-related underwater electric field, an induced electric field is generated by the variation of the magnetic flux in the adjacent space during the motion, rolling, or swaying of a magnetic object. Vessels, underwater vehicles, and their corresponding rotating accessories, such as the main axis and propeller, contain ferromagnetic metals with residual magnetism in most cases. A large magnetic field is also caused if these metals are in a geomagnetic field for a long time and the metals become magnetized. In underwater target detection, electric field detection is gradually combined with underwater moving platforms, and the research focus on moving platforms has gradually shifted from instability platforms, such as buoys and submersibles, to platforms with good underwater mobility and a larger detection range, such as unmanned boats and UUVs. As for a detection platform, the electric field induced by the motion of a magnetic object exists as a background disturbance in the underwater object detection of the platform. The induced electric field should, therefore, be inhibited.