A portable frequency domain electromagnetic system for shallow metal targets detection

In this paper, a portable frequency domain electromagnetic system CEM-2 is presented for shallow metal targets detection. This paper discusses the detection principle of frequency domain electromagnetic system, introduces hardware implementation, presents test results of each module, and gives the system’s imaging results in field tests. Sinusoidal pulse width modulation technique is employed in this system to produce single-frequency or multi-frequencies synthetic electromagnetic signals with signal to noise ratio of about 85 dB. After integration, the CEM-2 system’s in-phase noise level is about 90 ppm while the quadrature response is about 100 ppm. The experiment results of CEM-2 agree well with the simulation ones both from signatures and amplitudes. The experiment for detecting targets of different sizes and materials conducted in field indicates that CEM-2 system can be used to distinguish metallic and ferrous objects.