1. a Department of Electrical Engineering Korea Advanced Institute of Science and Technology (KAIST) 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Korea
2. b Agency for Defense Development Yuseong P. O. Box 35-3, Daejeon 305-600, Korea
3. c Agency for Defense Development Yuseong P. O. Box 35-3, Daejeon 305-600, Korea
4. d Agency for Defense Development Yuseong P. O. Box 35-3, Daejeon 305-600, Korea
5. e Department of Electrical Engineering Korea Advanced Institute of Science and Technology (KAIST) 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Korea