1. College of Electronic Engineering and Automation, Guilin University of Electronic Technology, Guilin 541004, P. R. China
2. Guangxi Key Laboratory for Nonlinear Circuit and Optical Communication, (Guangxi Normal University), Guilin, Guangxi 541004, P. R. China
3. Office of State Asset Management, Guilin University of Electronic Technology, Guilin 541004, P. R. China