1. a Department of Electronic Engineering, Ming-Chuan University, Taipei, Taiwan;, Email: sm.deng@msa.hinet.net
2. b Department of Electronic Engineering, Ming-Chuan University, Taipei, Taiwan
3. c Department of Electrical Engineering, Feng-Chia University, Taichung, Taiwan
4. d Department of Electrical Engineering, Feng-Chia University, Taichung, Taiwan