1. Department of Broadband Infocommunications and Electromagnetic Theory, Budapest University of Technology and Economics, Egry J. u. 18, H-1521 Budapest, Hungary
2. Laboratoire de Génie Electrique de Paris, CNRS – Supélec – UPS – UPMC, 11 rue Joliot-Curie, 91192 Gif-sur-Yvette Cedex, France