1. Department of Communication Engineering, Federal University of Rio Grande do Norte, UFRN, Caixa Postal 1655, CEP: 59078-970, Natal, RN, Brazil
2. Group of Telecommunications and Applied Electromagnetism, Federal Institute of Education, Science and Technology of Paraíba, IFPB, Av. Primeiro de Maio 720, CEP: 58015-430, João Pessoa, PB, Brazil