1. North University of China, Key Laboratory of Instrument Science and Dynamic Measurement, Ministry of Education, Taiyuan, Shanxi 030051, China
2. Beijing Jiaotong University, School of Electronic and Information Engineering, Beijing 100044, ChinacTsinghua University, Institute of Microelectronics, Beijing 100044, China
3. Beijing Jiaotong University, School of Electronic and Information Engineering, Beijing 100044, China
4. Tsinghua University, Institute of Microelectronics, Beijing 100044, China