The objective of the thesis is to experimentally characterize a shaped antenna system on a target, in a difficult case where the various entities are strongly coupled. An original method consists in measuring the waves backscattered by the carrier under test equipped with antennas, by connecting these to different load impedances, and thus to carry out measurements in reflection, in an anechoic chamber, taking into account the advantages but also the constraints associated with this means. The equations must be established, allowing to trace the characteristics of the antennas according to the RCS (Radar Cross Section) measured for the various loads. These being by nature non-linear, a search for solutions (analytical and/or algorithmic) will have to be conducted. Parametric analyses will then have to identify the sensitivity of the method to the choice of loads and the intrinsic characteristics of the antennas. Variations of the method exist, for example by dissociating temporally the various internal phenomena. A characterization prototype will have to be realized, allowing to reach the desired characteristics by measurement. A metrological study will have to allow to quantify the uncertainties of measurement of the various methods and their impacts on the parameters of interest. The final objective of this thesis is to establish the perimeters of use (performances and limits) of this method and its of this method and its variants, and to compare them to more classical methods.