1. School of Electronic and Information EngineeringSouth China University of TechnologyGuangzhouPeople's Republic of China
2. School of Electronics and InformationGuangdong Polytechnic Normal UniversityGuangzhouPeople's Republic of China
3. National Engineering Technology Research Center for Mobile Ultrasonic DetectionGuangzhouPeople's Republic of China
4. School of Electrical and Computer EngineeringGeorgia Institute of TechnologyAtlantaUSA