Professor Yang Xin's research group at the School of Electrical and Information Engineering, Hunan University, in collaboration with Professor Zhu Xuefeng from Huazhong University of Science and Technology, Academician of the Chinese Academy of Engineering and Dean Ouyang Xiaoping's team from the School of Materials Science and Engineering at Xiangtan University, and Professor Andrea Alù from the City University of New York, have created a digital Non-Foster system in the field of high-power acoustic emission for the first time, using digital control technology and silicon carbide MOSFET switch devices.
By controlling the amplitude correlation between the port output voltage and current, this system synthesizes real-time "counterintuitive" negative impedance characteristics with dispersion effects, enhancing the bandwidth of subwavelength resonant systems. This breakthrough surpasses the Chu physical limit in acoustic conversion, offering significant potential applications in long-distance information transmission and detection using sound waves and electromagnetic waves. The achievement was published in Nature Communications on May 21.
Non-Foster components, also known as "negative capacitance" or "negative inductance," defy Foster's reactance theory and do not exist naturally, requiring active devices and negative impedance transformation for realization.
Since the inception of Non-Foster components, understanding and research on them have been continuously explored and expanded. However, analog Non-Foster circuits have limitations in available parameter space due to passive RLC component values and tolerances, making continuous real-time adjustments impossible. Existing Non-Foster components struggle to fully utilize their broadband matching capabilities and practical application potential.
Professor Yang Xin's research group achieves real-time synthesis of equivalent negative impedance characteristics with dispersion effects by arbitrarily controlling the amplitude correlation between port output voltage and current. Through a pre-compiled adaptive proportional-resonant controller in a digital microprocessor, excellent active tracking performance and real-time adjustable capabilities at different operating frequencies are achieved. Furthermore, a leap in power levels is achieved using switch power electronic devices.
Most importantly, the team ensures the stability of the transfer function's poles in a large parameter range within the stable region of the complex plane through controller design, successfully avoiding the inherent instability of Non-Foster circuits. The proposed digital Non-Foster circuit provides stable, real-time equivalent negative impedance characteristics with dispersion effects in long-distance image transmission processes. Compared to analog Non-Foster matching networks, it increases the operating bandwidth of acoustic emission devices by more than five times and enhances power processing capabilities by over three orders of magnitude. The principles and methods can be widely applied in various subwavelength resonant system equipment, holding significant engineering application value.
Experimental setup diagram and results comparison diagram in the airwave transmission system. Images provided by the participants.
The reviewers of the paper believe that this research is of significant importance to the field and deserves attention; it is much more flexible than the widely studied linear non-Foster matching, and can provide higher levels of operating power and better efficiency.
The research was supported by the National Natural Science Foundation and the Hunan Talent Gathering Engineering Project. In addition, Professor Yang Xin's research group has applied for 17 patents (10 of which have been granted) in the field of high-power electroacoustic emission.
Related paper information: Link to the paper
