1. Laboratory of Electronics and Signal Processing, Department of Physics, Faculty of Science, University of Dschang, P.O. Box 67, Dschang, Cameroon
2. Department of Physics, Faculty of Science, University of Douala, P.O. Box 24157, Douala, Cameroon
3. Laboratory of Mechanics and Modeling of Physical Systems, Faculty of Science, University of Dschang, P.O. Box 67, Dschang, Cameroon