1. Department of Electrical Engineering, Ecole Polytechnique de Masuku (USTM), Franceville, Gabon
2. Department of physics sciences, Laboratory of multidisciplinary, Ecole Nationale Supérieure (ENS), Franceville, Gabon
3. Faculté de Sciences Physiques, Laboratoire de Modélisation et Simulation de Composant (LMSC), Ecole Polytechnique de Masuku (USTM), Franceville, Gabon