Affiliation: | 1. Electric and Electronic Department, University of Oviedo, Campus de Viesques, Edificio 3, E-33204 Gijón, Spain, E-Mail: marcos@ate.uniovi.es;2. Etronecology, S. L., Plaza Primo de Rivera, 1, E-33001 Oviedo, Spain, E-Mail: etron@netcom.es |