1. Department MHS, FGAN-FHR, D-53343 Wachtberg, Germany, essen@fgan.de
2. Department MHS, FGAN-FHR, D-53343 Wachtberg, Germany
3. Fraunhofer IAF, D-79108 Freiburg, Germany, Michael.Schlechtweg@IAF.Fraunhofer.de
4. Fraunhofer IAF, D-79108 Freiburg, Germany