Hsing-Chung Liang and Chung Len Lee
Department of Electronic Engineering
Chang Gung University
Taoyuan, Taiwan 333, R.O.C.
E-mail: hcliang@mail.cgu.edu.tw
+Department of Electronics Engineering
National Chiao Tung Unviersity
Hsinchu, Taiwan 300, R.O.C.
E-mail: cllee@cc.nctu.edu.tw