sensors Article Electromagnetic Detection System with Magnetic Dipole Source for Near-Surface Detection Xian Liao 1 , Zhengyu Xu 1,*, Wei Liu 2, Heng-Ming Tai 3, Jie Zhou 1, Xiao Ma 1 and Zhihong Fu 1 1 School of Electrical Engineering, Chongqing University, Chongqing 400044, China; ...