An investigation of time-reversal techniques in seismic landmine detection

Time-reversal focusing of elastic waves in inhomogeneous media: an application to an elastic-wave landmine detection system

“…Time-reversal focusing has demonstrated significant improvements in surface displacements at a focus point when compared to other excitation methods. 2 The previous study by Norville et al observed no evidence of the super-resolution phenomenon which has been observed in other examinations of time-reversal focusing 3 and is predicted by theoretical examinations of super-resolution. 4,5 Results are generated using a three dimensional finite-difference time-domain model of elastic wave propagation.…”

“…The theory of time-reversal focusing and it's implementation have been well documented in the literature. 2,[6][7][8] For this reason, only a brief introduction is offered here and the reader is encouraged to consult the references for further detail.…”

Time-reversal focusing of elastic surface waves with an asymmetric surface layer

“…The signal used to interrogate the soil is a swept frequency chirp signal that sweeps from 30 Hz to 2 kHz. 15 For display purposes, the results are presented as the response to a differentiated Gaussian pulse with a center frequency of 900 Hz. The process used to create the time-reversal drive signals is described in earlier work.…”

“…1). 11,13 A large concrete wedge-shaped tank is filled with approximately 50 tons of damp compacted sand. Sand is chosen as the background medium because its seismic properties are similar to many types of soil, and because it is straightforward to recondition disturbed sand.…”

“…Only limited-scale studies in any type of granular media have been performed, 10,11 indicating a need for further study. The complexity of wave propagation in soil goes beyond that of many common fluids or elastic media.…”