1. Graduate Institute of Electronics Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan
2. Research Center for Applied Sciences, Academia Sinica, No. 128, Sec. 2, Academia Road, Taipei 11529, Taiwan
3. Department of Electrical Engineering, National Cheng Kung University, No. 1, University Road, Tainan City 701, Taiwan