An IR-RIME-SQP-Based Spectrum Modification Method for Shallow Surface Electromagnetic Detection Transmitting Scheme of Metal Traps in Forested Areas

In the electromagnetic detection of shallow subsurface metal snaring traps in forested areas, conventional transmission schemes such as square waves, PRBS and PSO waveforms inevitably excite severe clutter in soils exhibiting viscous remanent magnetization (VRM), which drastically degrades the signal-to-clutter ratio (SCR). To resolve this issue, this paper proposes a spectrum modification method for the transmitting scheme based on an Interval Robust hybrid RIME and Sequential Quadratic Programming (IR-RIME-SQP) algorithm. By coupling the Debye relaxation characteristics of ferromagnetic targets with the soil VRM model, the proposed method concentrates limited transmission energy into a bell-shaped frequency window near the target’s characteristic frequency. Furthermore, interval analysis is introduced to ensure robust performance against the dynamic drift of coil parameters. The feasibility of this novel transmitting scheme is validated through ablation experiments and comparative simulations. Finally, laboratory measurements demonstrate that IR-RIME-SQP provides a more rational and efficient energy allocation strategy, improving the targeted frequency energy retention (TFER) by approximately 16.4% and thereby enhancing both detection efficiency and precision.