1. Institut für Mikrowellentechnik und Photonik, Technische Universität Darmstadt; Merckstraße 25 64283 Darmstadt Germany
2. Department of Information Technologies, Mathematics and Physics Comrat State University; Galatsan Street 17 MD-3800 Comrat Moldova
3. Department of High Frequency Electronics Technische Universität Darmstadt; Merckstraße 25 64283 Darmstadt Germany
4. Faculty of Physics and Engineering Moldova State University; A. Mateevici Street 60 MD-2009 Chisinau Moldova