1. Department of Electrical and Computer Engineering, Duke University, Durham, NC, USA
2. Department of Electrical and Computer Engineering, Rhineland-Palatinate Technical University, Kaiserslautern, Germany
3. Research Centre for Electric Vehicles and Department of Electrical and Electronic Engineering, The Hong Kong Polytechnic University, Hong Kong
4. Department of Electrical Engineering and the State Key Laboratory of Terahertz and Millimeter Waves, City University of Hong Kong, Hong Kong, SAR, China