[1] Department of Electrical Engineering, Nagoya University, Nagoyo, 464, Japan
[2] Fuji Electric Co., Ltd., Kawasaki, 210, Japan
[3] Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Toyohashi, Japan
[4] Department of Electronic Engineering, Mie University, Tsu 514, Japan
[5] Department of Electrical Engineering, Nagoya University, Nagoyo, 464, Japan