[1] Saule Technol, Wroclaw Technol Pk,11 Dunska St,Sigma Bldg, PL-54130 Wroclaw, Poland
[2] Univ Roma Tor Vergata, Dept Elect Engn, Via Politecn 1, I-00133 Rome, Italy
[3] Saule Res Inst, Wroclaw Technol Pk,11 Dunska St,Sigma Bldg, PL-54130 Wroclaw, Poland
[4] Poznan Univ Tech, Fac Mat Engn & Tech Phys, Piotrowo 3, PL-60965 Poznan, Poland