1. School of Electrical and Computer Engineering, National Technical University of Athens, 15780 Athens, Greece
2. Department of Electrical and Computer Engineering, University of Western Macedonia, 50100 Kozani, Greece
3. Interuniversity Microelectronics Centre (IMEC), 3001 Leuven, Belgium
4. Associated Division ESAT-INSYS (INSYS), Integrated Systems, KULeuven, Kapeldreef 75, 3001 Leuven, Belgium