1. Universidade Federal de Minas Gerais,Graduate Program in Electrical Engineering,Belo Horizonte,MG,Brazil,31270-901
2. Centro Federal de Educacão Tecnológica de Minas Gerais,Department of Electrical Engineering,Belo Horizonte,Brazil
3. Universidade Federal de Minas Gerais,Department of Electrical Engineering,Belo Horizonte,Brazil