International audienceThe feasibility of generating arbitrary wavefronts within a time-reversal electromagnetic chamber (TREC) has been demonstrated both theoretically and experimentally. Though originally motivated for EMC tests, the generation of coherent wavefronts within a reverberating cavity has a potential interest in antenna testing, too. In this paper, the generation of locally planar wavefronts is addressed by means of numerical simulations involving a 2D cavity, for a scalar electric field. The relationship between the quality of the wavefronts and its defining parameters (bandwidth, curvature, phase center, etc.) is investigated