[1] Hiroshima Univ, Fac Engn, Hiroshima, Japan
[2] Tohoku Univ, Res Inst Elect Commun, Sendai, Miyagi, Japan
[3] Univ Twente, Fac Appl Phys, Low Temp Div, Enschede, Netherlands
[4] Saitama Univ, Fac Engn, Dept Elect & Elect Syst, Saitama, Japan
[5] Inst Elect Informat & Commun Engineers Japan, Tokyo, Japan
[6] Inst Elect Engn Japan, Tokyo, Japan