[1] Department of Electrical Engineering, Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550, Japan
[2] Sumitomo Electric Industries, Ltd., 5-33 Kitahama 4-chome, Chuo-ku, Osaka 541-0041, Japan
[3] Kyocera Corp., 6 Takeda Tobadono-cho, Fushimi-ku, Kyoto 612-8501, Japan