1. a Graduate Institute of Communications Engineering, and Department of Electronic Engineering, National Changhua University of Education, 1 Jin-De Road, Changhua, Taiwan 500, R.O.C.
2. b Graduate Institute of Communications Engineering, and Department of Electronic Engineering, National Changhua University of Education, 1 Jin-De Road, Changhua, Taiwan 500, R.O.C.;, Email: iecher@cc.ncue.edu.tw
3. c Department of Electrical Engineering, National Yunlin University of Science and Technology, 123 University Road, Section 3, Douliou, Yunlin, Taiwan 640, R.O.C.