1. Department of Electrical and Computer Engineering, National University of Singapore, Singapore 119260
2. A*STAR Institute of Microelectronics, Singapore 117685
3. National University of Singapore (Suzhou) Research Institute, Suzhou 215123, China
4. Department of Electrical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
5. Industrial Technology Research Institute, Chutung 31040, Taiwan