Design and Optimization of Dual-Coil Passive Magnetic Field Amplification System

In underwater magnetic detection, the challenge of capturing weak magnetic signals due to environmental noise and long-distance magnetic signal attenuation remains an urgent optimization problem. To address this issue, we introduce a passive magnetic field amplification system composed of two solenoids with different configurations, serving as a pre-stage device for magnetic sensors to achieve magnetic field convergence and enhance the magnetic flux density directly measured by the sensing equipment. The equivalent circuit model of the passive system was first derived through theoretical analysis, establishing the corresponding gain expression. Subsequently, a high-precision inductance computation method based on numerical integration was implemented, coupled with high-performance computing resources to conduct systematic parametric analysis of key operational parameters. Finally, validation experiments conducted on the COMSOL Multiphysics simulation platform demonstrate that the relative error between theoretical calculations and simulation data is controlled within 2%, confirming the engineering feasibility of this optimization scheme.