Arrays of phase-shifted antennas, made of several singleelement antennas, are commonly used in air radar and communication systems to obtain very directive radiation patterns. In this paper, we propose to apply this technology to GPR. Firstly, a theoretical study of linear arrays is presented, allowing to determine the influences of the element number, their spacing and phase-shift. Secondly, field experiments have been carned out, consisting of Common Receiver Gathers with two single 100 MHz antennas, in order to reconstruct sections acquired with arrays of 21 transmitters and a single receiver. The results lead to greater signal to noise ratios and penetration depths. Lastly, with the aim to build an actual array of transmitters, antennas of several kinds have been made and tested.