1. a Department of Electronic Engineering, Ching Yun University, Jung-Li 320, Taiwan, R.O.C.;, Email: yfc01@cyu.edu.tw
2. b Department of Electronic Engineering, Ching Yun University, Jung-Li 320, Taiwan, R.O.C.
3. c Department of Physics, National Taiwan University, Taipei 10617, Taiwan, R.O.C.