Design of an improved dipole antenna for detecting enclosure structure defects by crosshole GPR

In underground engineering, the enclosure structure is the most critical part to guarantee the safety of construction. However, defects such as voids or cracks might appear in the structure, which will lead to accidents of foundation pit. In this paper, an improved dipole antenna is designed for detecting enclosure structure defects by a stepped frequency crosshole Ground Penetrating Radar (GPR). In order to obtain more desirable performance, the antenna parameters including the half-cone angle θ, the feeding gap g, the cylinder radius r and the cylinder length l are designed and optimized by the FEM method. The optimized antenna has a center frequency of 0.52GHz and can work well in the frequency range from 0.45GHz to 1.55GHz. Moreover, the antenna is fabricated and tested in a physical model. The result shows that the designed antenna has good performance and can serve for enclosure structure defects detection.