Volume 12, Issue 3 (September 1989)
Pulse Shapes from Ground Penetrating Radar
A number of technical reports have discussed the use of ground penetrating radar equipment in examining highway structures for deterioration. Several of these reports provide expressions or calculational techniques that purport to describe the shape of the radar pulse returning from voids within the structure, such as the thin air gap at a delamination within a concrete bridge deck or the larger voids that can develop between a concrete slab and the soils beneath. None of the theories has been developed with the use of correct electromagnetic theory (Maxwell's equations and a two-interface reflection coefficient); it is not surprising, therefore, that the pulse shape computations and observed pulse shapes sometimes fail to agree. In this paper the correct means of computing the shape of radar pulses returning from voids is presented with some results, and new approaches for computerized detection of structural defects are discussed.