1. Deptartment of Electrical Engineering, Kwangwoon University, 447‐1, Wolgye‐Dong, Nowon‐Gu, Seoul, Korea
2. Korea Electrotechnology Research Institute, Changwon, Korea
3. Department of Electrical Engineering, Kwangwoon Graduate School, 447‐1, Wolgye‐Dong, Nowon‐Gu, Seoul, Korea