1. Department of Electrical and Electronic EngineeringRitsumeikan University 1‐1‐1 Nojihigashi Kusatsu Shiga 525‐8577 Japan
2. Ritsumeikan Global Innovation Research OrganizationRitsumeikan University 1‐1‐1 Nojihigashi Kusatsu Shiga 525‐8577 Japan
3. Department of Electrical and Electronic EngineeringTokyo Institute of Technology Meguro‐ku Tokyo 152‐8552 Japan
4. Atsugi Research CenterAdvanced Technology Research LaboratoriesIdemitsu Kosan Co.,Ltd. Atsugi Kanagawa 243‐0206 Japan