Phased-array transmitters for GPR surveys

Abstract

The antennas commonly used in ground penetrating radar surveys have wide illumination, but limited spatial resolution. To overcome this limitation, we propose the use of phased-array transmitters, which allow us to direct the electromagnetic energy. We first perform a theoretical analysis to determine the influence of the number of antennas, the antenna spacing and the phase shifts between antennas. This analysis is useful to define the direction of the main lobe of the radiation pattern and its width. The simulations, which show the versatility of using phased arrays as compared to a single antenna, have been done to determine the best array parameters to image a given interface. On the basis of these simulations, we acquired common-receiver gathers with two single 100 MHz antennas to simulate a single survey involving 21 phase-shifted transmitter antennas and a single-receiver antenna. We have improved the signal-to-noise ratio, and the lateral coherence of the reflection events, and obtained a greater penetration depth as a consequence of the energy focusing.