[1] Grad. Sch. of Sci. and Engineering, Saitama Univ., 255 shimo-ohkubo, Urawa 338-8570, Japan
[2] Div. Electron. Telecommunication E., Kwandong University, 7 Imchun-li, Yangyang-up, Yangyang-gun, Kangwon-do, Korea, Republic of
[3] Tosoh Hyuga Corporation, 1 Funabatyou, Hyuga 883-0065, Japan