1. a Institute of Computer and Communication Engineering, Department of Electrical Engineering, National Cheng Kung University, Tainan, Taiwan, R.O.C.
2. b Institute of Computer and Communication Engineering, Department of Electrical Engineering, National Cheng Kung University, Tainan, Taiwan, R.O.C.
3. c Department of Electronic Engineering, National University of Tainan, Tainan, Taiwan, R.O.C.;, Email: cychen57@mail.nutn.edu.tw