A Wigner-Ville, time-frequency approach to TNT detection in nuclear quadrupole resonance experiments

To minimize the risks involved in humanitarian demining requires a sensitivity setting close to unity, resulting in a very high false alarm rate. Nuclear quadrupole resonance detection, based on the spin echoes from nuclear spin relaxation, is a promising example of a highly specific detector that directly addresses the properties of the explosive rather than the mine casing. However, the data aquisition time necessary to obtain a sufficiently high sensitivity is long due to the extremely poor signal-to-noise-ratio of the spin echoes. Besides improvements in the hardware, it is important to pursue better signal analytic techniques. We present a time-frequency approach based on theWigner-Ville quasi-distribution for the analysis of nuclear quadrupole resonance data. We calculate ROC curves for real data obtained under laboratory conditions and show the technique presents a substantial improvement over popular demodulation techniques, especially for signals with poor signal-to-noise ratio.