1. a Department of Electronic Engineering , National Taiwan University of Science and Technology , No. 43, Sec.4, Keelung Rd., Taipei 106, Taiwan, R.O.C. Phone: Fax: E-mail:
2. b Department of Electronic Engineering , National Taiwan University of Science and Technology , No. 43, Sec.4, Keelung Rd., Taipei 106, Taiwan, R.O.C.