Résumé
Near-field vector measurement can be used toimage devices or material. From optics to microwaves, thistechnique uses different method and theoretical supports. Ourtest bench, working in the band 55 to 65 GHz and its capacity toimage a buried structure on a commercial chip from GaN systemare presented here. The influence of the bow-tie probe shape andthe distance of measure is discussed. The capacity of our systemto image a buried structure is detailed thought the informationof modulus and phase of the near field reflected voltage.