1. a Department of Electronic Engineering, Ming-Chuan University, Taipei, Taiwan, R.O.C.
2. b Department of Electronic Engineering, Ming-Chuan University, Taipei, Taiwan, R.O.C.
3. c Department of Electrical Engineering, Feng-Chia University, Taichung, Taiwan, R.O.C.
4. d Department of Electrical Engineering, Feng-Chia University, Taichung, Taiwan, R.O.C.