**Author details**

José R. Montejo-Garai1 \*, Jorge A. Ruiz-Cruz2 and Jesús M. Rebollar1

1 Grupo de Electromagnetismo Aplicado, Information Processing and Telecommunications Center, Universidad Politécnica de Madrid, Madrid, Spain

2 Escuela Politécnica Superior, Universidad Autónoma de Madrid, Madrid, Spain

\*Address all correspondence to: jr@etc.upm.es

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
