Changjun Liu

Dr. Liu received a B.S. degree in applied physics from Hebei University, Hebei, China, in 1994, and an M.S. degree in radio physics and a Ph.D. degree in biomedical engineering from Sichuan University, Sichuan, China, in 1997 and 2000, respectively. From 2000 to 2001, he was a post-doctoral researcher at Seoul National University, Seoul, Korea. From 2006 to 2007, he was a visiting scholar at Ulm University, Ulm, Germany. Since 1997, he has been with the School of Electronics and Information Engineering at Sichuan University, where he has been a professor since 2004. He is the executive deputy director of the key laboratory of Wireless Power Transfer of the Ministry of Education, China. He was a senior member of the IEEE and CIE (Chinese Institute of Electronics). From 2006 to 2010, he was an outstanding reviewer for the IEEE Transactions on Microwave Theory and Techniques. He has been the Academy and Technology Leader in Sichuan province since 2023 and was honored with the New Century Excellent Talents at Universities in China from 2009 to 2012. He is the associate editor of IEEE Microwave Wireless Technology Letters and topic editor of IEEE Journal of Microwaves. Dr. Liu has authored two books and more than 200 articles. His current research interests primarily focus on microwave and millimeter-wave wireless power transmission. In his research, he has explored a range of frequencies, from S-band to X-band, for wireless power transmission systems spanning distances from meters to kilometers. He has also done research on wireless power transmission in closed cavities. Additionally, he has conducted studies on microwave rectifiers to optimize their efficiencies and dynamic power ranges. He has been the sole investigator of more than sixteen grants from both government and industry, including six funds from the National Nature Science Foundation of China.

Microwave Wireless Power Transmission (MWPT) is a transformative technology that enables long-distance energy delivery for critical applications such as Space-Based Solar Power (SBSP), aviation power, and wireless sensor networks for the Internet of Things (IoT). To transition from laboratory concepts to ubiquitous real-world deployment, MWPT systems must overcome significant bottlenecks regarding rectification efficiency and operational adaptability. This lecture details advanced methodologies for achieving high-efficiency microwave rectification and extending the dynamic power range. We first address the limitations of conventional rectifier designs, which often suffer from large footprints and high insertion losses due to bulky band-pass filters. A novel topology is presented that utilizes a series band-stop structure—specifically a short-ended λg/8 transmission line—to facilitate effective harmonic recycling while significantly reducing the circuit size. Furthermore, maintaining high conversion efficiency under fluctuating input power levels is a major challenge for traditional rectifiers. By leveraging the nonlinear impedance characteristics of Schottky diodes and implementing adaptive impedance matching, we have developed power-adaptive rectifiers. These designs demonstrate an ultra-wide 31 dB power dynamic range (spanning from -1 dBm to 30 dBm). The lecture concludes with a forward-looking vision for MWPT’s future. We explore how these technical breakthroughs will enable global energy solutions through Solar Power Satellites (SPS), seamless consumer device charging, and powering humanoid robots in industrial environments. Attendees will gain a comprehensive understanding of how innovative circuit design is driving the evolution of microwave energy into a daily reality