Modelling and processing of ultra wide band scattering of buried targets

Among the techniques which may be proposed for detection and reconnaissance of abandoned mines, very short pulse scattering analysis should be very helpful, by itself or combined with other sensors information. It is well known that the field scattered by a target illuminated by an ultra wide band (UWB) pulse contains a lot of information: high resolution imaging (location and strength of diffracting centers), dispersive phenomena and resonances, to which could be added polarimetric characteristics for example, which should be very useful to detect and identify abandoned mines. Apart from data acquisition, simulation of electromagnetic behaviour of such scenarios is essential to determine what is, on a given impulse response, the impact of the numerous parameters involved in the scenario description and by the way help and orient the subsequent signal processing. Among these parameters should be included those related to the medium (surface roughness, volume heterogeneities, frequency dispersion...) as well as those related to the measurement system and in particular the pulse shape. The point is then to be able to extract the supposed discriminating features from the received scattered signals, and computations should be accurate enough to highlight these features without introducing numerical artefacts. This paper deals with finite difference in time domain (FDTD) scattering modelling, results and processing of such scenarios. EM modelling of UWB diffraction, UWB scattering in free space, and UWB scattering of buried objects are discussed