1 School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore
2 State Key Laboratory of Millimeter Waves, Southeast University, Nanjing 210096, China
3 Electrical Engineering, Kulicke & Soffa Pte. Ltd., Singapore 554369, Singapore
4 School of Microelectronics Science and Technology, Sun Yat-sen University, Zhuhai 519082, China
5 School of Information and Engineering, Shandong University, Qingdao 266237, China
6 School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
7 e-mail: zhangjingjing@seu.edu.cn
8 e-mail: qjwang@ntu.edu.sg
9 e-mail: luoyu@ntu.edu.sg