1. Ph.D. Program in Electrical and Comm. Engineering Department; Feng Chia University; Taichung 40724 Taiwan Republic of China
2. Department of Electrical Engineering; Chien Hsin University of Science and Technology; Chung-Li, Tao-yuan, 32097 Taiwan Republic of China
3. Department of Electrical Engineering; Feng Chia University; Taichung, 40724 Taiwan Republic of China