1. Department of Engineering, University of Sannio, Benevento, Italy. E-mail: giuseppe.cardone@unisannio.it
2. Moscow Institute of Radio Engineering, Electronics and Automation, Technical University, Moscow, Russia. E-mail: pas-se@yandex.ru
3. DSGA, University of Sannio, Benevento, Italy. E-mail: cperugia@unisannio.it