1. Fraunhofer Institute for Physical Measurement Techniques IPM, Georges-Köhler-Allee 301, 79110 Freiburg, Germany
2. Fraunhofer Institute for Machine Tools and Forming Technology IWU, Nöthnitzer Str. 44, 01187 Dresden, Germany
3. Fraunhofer Institute for High Frequency Physics and Radar Techniques FHR, Fraunhoferstraße 20, 53343 Wachtberg, Germany