1. School of Microelectronics, Southern University of Science and Technology, Shenzhen 518055, China
2. Department of Electrical and Electronic Engineering (Joint Appointment with School of Biomedical Sciences), The University of Hong Kong, Pokfulam Road, Hong Kong, China
3. Engineering Research Center of Integrated Circuits for Next-Generation Communications, Ministry of Education, Southern University of Science and Technology, Shenzhen 518055, China