1. Department for Electrical EngineeringUniversity of Applied Sciences OffenburgBadstraße 24D‐77652OffenburgGermany
2. Department of Measurement and ControlKarlsruhe Institute of TechnologyEngler‐Bunte‐Ring 21D‐76131KarlsruheGermany
3. Department of ElectronicsTechnical University of Sofia8, Kliment Ohridski Blvd.BG‐1756SofiaBulgaria