oa Applicability of phased array antenna to ground penetrating radar

Ground Penetrating Radar (GPR) has been widely used to detect objects in shallow subsurface. Although a bow-tie antenna, which is the major antenna in practice, provides clear cross sections in the shallow subsurface especially under survey line, the resolution in the direction of cross-line depends strongly on the spatial interval between neighboring survey lines. Moreover, no subsurface image could be obtained for subsurface beneath complex artificial structures on the surface since no survey line may be drawn above the structures. These are the two major problems in the current practice of GPR surveys. We would like to propose a method to overcome these two problems with the use of phased array antenna as a radar source. We conducted some numerical simulations usuing a 3D-FDTD method and examined the performance of the antenna in terms of signal-to-noise ratio of the generated electromagnetic (EM) wavefield and response to slanted EM wavefield input. Our numerical resuts indicate that the application of the phased array system to GPR could enhance the signal-to-noise ratio for reflectors located lateral to the survey line, and has a potential to be used as an angular scanner imaging tool that has not been attempted in the conventional GPR system. The latter may also indicate that the number of survey lines could be reduced to lower the cost of GPR surveys.