High Efficiency Distributed Beamforming RF Energy Transfer using a Closed-loop Energy Receiver

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The amount of ambient radio frequency (RF) energy, such as those from Wi-Fi and Bluetooth transmitters, is continuing to increase due to the proliferation of internet-of-things (IoT) devices in our environment. However, the underlying technological challenges have hindered the effective combination of energy from multiple transmitters by using distributed beamforming to harvest useful RF energy for a remote IoT device. This project aims to overcome these technological challenges to develop a high-efficiency distributed beamforming technique to combine energy from multiple RF transmitters and direct it to a remote IoT energy receiver. The project also aims to develop a high-efficiency RF-to-DC converter circuit. It will enable a new technique for harvesting RF energy which will be useful for IoT, biomedical, and remote sensing applications. These techniques are transformative for harvesting RF energy with beamforming capability at ultra-low power levels. The research outcomes from this project will be integrated with a graduate-level curriculum offering, a power management integrated circuits (PMIC) course. All designs and results of this project will be made public on the project website. This project will also engage undergraduate and high school students through a high school summer internship program and the Northeastern University’s Undergraduate Program for Leaders In Future Transformation (UPLIFT) program. The project team will work with the College of Engineering Multi-Cultural Engineering program to increase the diversity of students engaged in NSF Research Experiences for Undergraduates (REU) program. The graduate and undergraduate students participating in this project will be trained on semiconductor chip design. This project aims to develop a high-efficiency distributed beamforming-based RF energy harvesting technique that combines energy from multiple RF energy transmitters and directs it toward a remotely located energy receiver. Effective distributed beamforming requires closed-loop optimization between energy transmitters and the energy receiver. However, the overhead power consumption of sensing and communication needed to realize closed-loop optimization render conventional distributed beamforming techniques inefficient. To overcome the overhead power consumption of communication, this project will develop a new backscatter communication method. The backscatter communication system will enable an ultra-low-power feedback technique for closed-loop optimization. For sensing phase and frequency offset among energy transmitters, a new ultra-low-power energy detection-based sensing platform will also be developed. The project also aims to develop a new RF-to-DC rectifier topology to enable high-efficiency RF energy harvesting across a wide range of received power levels. Accompanying the RF-to-DC converter design will be a maximum power tracking scheme that will provide output impedance matching to realize maximum efficiency operating point for the rectifier. The combination of beamforming, high-efficiency RF-to-DC conversion, ultra-low-power sensing, and backscattering communication will enable a significant increase in RF energy harvesting. The project also includes development of an RF energy transfer protocol to be implemented in wireless networks. A hardware demonstration of the proposed solutions will be carried out using test chips of the energy harvesting system.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.