School of Electrical Engineering, Korea University, Seoul 136-713, Korea.|School of Electrical Engineering, Korea University, Seoul 136-713, Korea.|School of Electrical Engineering, Korea University, Seoul 136-713, Korea.|School of Electrical Engineering, Korea University, Seoul 136-713, Korea.|School of Electrical Engineering, Korea University, Seoul 136-713, Korea.|School of Electrical Engineering, Korea University, Seoul 136-713, Korea.|School of Electrical Engineering, Korea University, Seoul 136-713, Korea.|School of Electrical Engineering, Korea University, Seoul 136-713, Korea.