Characterization and reduction of background noise for the detection of plastic anti-personnel landmine in mineralized soil

Abstract

If the continuous-wave electromagnetic induction (EMI) method is used to detect plastic anti-personnel (PAP) landmines in strongly mineralized soil, background noise may interfere with and further submerge the weak secondary field generated by the landmine. To analyze quantitatively the characteristics of this noise, a semi-space homogenous medium model was developed based on a cylindrical coordinate system. The results of simulation show that, in the signal of the background noise generated by the mineralized soil, the real component dominates whereas the imaginary component is insensitive to changes in the electromagnetic properties and sensor height. A noise reduction method based on the quadrature electromagnetic method is proposed. Assuming a spherical model for the ferromagnetic components of the PAP landmine, an optimal excitation frequency of the primary field was determined. By considering the phase shift in the sensor and signal processing circuit, a method was developed to determine a sensor pre-correction. In addition, an experimental platform was built that included a PCB-based double-D EMI sensor, a data acquisition card, and a three-dimensional scanning slideway. Experimental tests with a PAP landmine buried in clay, laterite, and magnetite produced results that corroborated the above theoretical analysis. The quadrature electromagnetic method is still able to detect secondary fields with high signal-to-noise ratio generated by the PAP landmine buried 15 cm deep in the magnetite.

Boundary-Element Analysis of Magnetic Polarization Tensor for Metallic Cylinder

“…Besides, from Faraday's Law, the received voltage can also be calculated as = 2 0 2 (21) Combining equation (20) and equation ( 21), it can be noticed that of the tensor is equal to the z-component of the scattered magnetic field. Besides, from the similar deviations, and also have this property, which can be obtained by the x and y components of the scatted magnetic field respectively.…”

“…The limit of the system is that it can detect the SS316 hypodermic needle piece with the length of 0.5 mm and a diameter of 650 μm and a weight of around 0.6 mg. A digital procession algorithm using dual channels was proposed by Bai et al to distinguish the metal and the product [18]. The design of sensor detector to cancel the coupling between the coils and balance the background field gives good performance in differentiating the landmine in mineralized soil [19][20]. However, it is still a challenge for researchers to classify the harmful metal object from a range of metal objects.…”

Classification of unexploded ordnance-like targets with characteristic response in transient electromagnetic sensing

“…Various geophysical methods have been used for UXO detection [5,6], such as magnetic detection, electromagnetic induction (EMI), and ground-penetrating radar. Among these methods, EMI sensing employs low frequencies ranging from tens of hertz to hundreds of kilohertz to increase sensitivity to conducting targets, but it leads to nearly complete loss in spatial resolution [7][8][9]. A series of forward models, such as the single dipole model [10], normalized surface magnetic source model [11], and orthonormalized volume magnetic source model [12], has been designed for target discrimination.…”