GPR inspection of asphalt pavement using an off-ground antenna array

We have published a ground-coupled GPR antenna array, which consists of one transmitter and five receivers, for in situ estimation of the thickness and dielectric permittivity of an asphalt pavement layer. In this paper, we optimize the design of the antipodal Vivaldi antenna to pursue a higher resolution through reducing the late-time ringing. Furthermore, an off-ground antenna array is assembled, and can effectively accelerate the acquisition of common-source GPR datasets. The antenna phase center was calibrated to estimate the velocity and thickness of both the air gap and asphalt pavement layer, through velocity spectrum analysis. Numerical experimental results show that the off-ground antenna array is one ideal method for inspecting asphalt pavements.