1. Department of Electrical Engineering and Information Technology, Circuit and System Technology Group, Heinz Nixdorf Institute, University of Paderborn, Paderborn, Germany
2. Wireless- and Transponder-Systems, Fraunhofer Institute for Microelectronic Circuits and Systems, Duisburg, Germany
3. Wireless Sensors and Systems, Fraunhofer Institute for Microelectronic Circuits and Systems, Duisburg, Germany