1. Department of Electrical Engineering; Federal Rural University of Semi-Arid (UFERSA), Rodovia RN-233, km 01; Caraúbas Rio Grande do Norte, CEP 59780-000 Brazil
2. Department of Communication Engineering; Federal University of Rio Grande do Norte (UFRN), Caixa Postal 1655; Natal Rio Grande do Norte, CEP 59072-970 Brazil