Nonlinear detection of land mines using wide bandwidth time-reversal techniques

Alexander Sutin; Brad Libbey; Victor Kurtenoks; Douglas Fenneman; Armen Sarvazyan

doi:10.1117/12.673714

18 May 2006 Nonlinear detection of land mines using wide bandwidth time-reversal techniques

Alexander Sutin, Brad Libbey, Victor Kurtenoks, Douglas Fenneman, Armen Sarvazyan

Proceedings Volume 6217, Detection and Remediation Technologies for Mines and Minelike Targets XI; 62171B (2006) https://doi.org/10.1117/12.673714
Event: Defense and Security Symposium, 2006, Orlando (Kissimmee), Florida, United States

Abstract

Time reversal acoustic (TRA) focusing allows concentration of elastic energy at a location in the soil being investigated to detect landmines. The TRA process is conducted by broadcasting a wide bandwidth signal and recording the surface vibration by a Laser Doppler Vibrometer (LDV). The system impulse response from speaker to the LDV output can then be computed by cross correlating the original and recorded signals for each channel. Each transducer re-radiates the time reversal impulse response. This provides efficient focusing of the seismic wave in both space and time, thus enhancing the nonlinear effects associated with soil and landmine vibrations. Using orthogonal initial signals the suggested TRA procedure can be implemented simultaneously with multiple transmitters to increase the scanning speed. The nonlinear effects were investigated using a phase inversion method where the TRA signal is broadcast a second time with an opposite sign and the two received signals are added in post processing. The summed signal contains mainly the results of nonlinear wave interaction and tends to cancel the linear response. Small scale land mine detection experiments were conducted using a laser Doppler vibrometer and an array of speakers in the frequency band 50-500Hz. They demonstrate that the TRA system provides high concentration of elastic wave energy in the tested area. The measurements of spectral density of the TRA focused signal reveal increased spectral density in the vicinity of mine resonance frequencies. The nonlinear TRA phase inversion method shows higher contrast between mine and no mine than the linear TRA method.

Citation Download Citation

Alexander Sutin, Brad Libbey, Victor Kurtenoks, Douglas Fenneman, and Armen Sarvazyan "Nonlinear detection of land mines using wide bandwidth time-reversal techniques", Proc. SPIE 6217, Detection and Remediation Technologies for Mines and Minelike Targets XI, 62171B (18 May 2006); https://doi.org/10.1117/12.673714

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