Characterization of transient bow-tie antennas for ground-penetrating radar

Abstract

In this paper a comprehensive characterization of transient bow-tie antennas for GPR applications is presented. In particular the characteristic impedance of a transient bow-tie antenna above different types of ground, as a function of its flare angle is given. The time-domain reflection coefficient of the transient bow-tie antenna above the ground is derived and also plotted as a function of flare angle. This result shows that there exists an optimal flare angle which gives minimal reflection at the antenna terminal for various ground types. Additionally, here we also investigate the characteristic impedance as a function of antenna elevation above the ground. Moreover, in this paper the subsurface footprints of bow-tie antennas as a function of flare angle for different ground types are shown. This result shows that depending on the target's size, the size of footprint can be adjusted by varying the flare angle in order to reduce clutter from ground surface. The analysis is carried out in the frequency-domain using the mixed-potential integral equation (MPIE) method for problems in multi-layer media, which is solved numerically by the method of moments. The solution in the time domain for transient antennas is obtained using the Fourier transform method and a time window technique to remove open-end reflections.