Dynamic Focusing of Large Arrays for Wireless Power Transfer and Beyond
We present architectures, circuits, and algorithms for dynamic 3-D lensing and focusing of electromagnetic power in radiative near- and far-field regions by arrays that can be arbitrary and nonuniform. They can benefit applications such as wireless power transfer at a distance (WPT-AD), volumetric sensing and imaging, high-throughput communications, and optical phased arrays. Theoretical limits on system performance are calculated. An adaptive algorithm focuses the power at the receiver(s) without prior knowledge of its location(s). It uses orthogonal bases to change the phases of multiple elements simultaneously to enhance the dynamic range. One class of such 2-D orthogonal and pseudo-orthogonal masks is constructed using the Hadamard and pseudo-Hadamard matrices. Generation and recovery units (GU and RU) work collaboratively to focus energy quickly and reliably with no need for factory calibration. Orthogonality enables batch processing in high-latency and low-rate communication settings. Secondary vector-based calculations allow instantaneous refocusing at different locations using element-wise calculations. An emulator enables further evaluation of the system. We demonstrate modular WPT-AD GUs of up to 400 elements utilizing arrays of 65-nm CMOS ICs to focus power on RUs that convert the RF power to dc. Each RFIC synthesizes 16 independently phase-controlled RF outputs around 10 GHz from a common single low-frequency reference. Detailed measurements demonstrate the feasibility and effectiveness of RF lensing techniques presented in this article. More than 2 W of dc power can be recovered through a wireless transfer at distances greater than 1 m. The system can dynamically project power at various angles and at distances greater than 10 m. These developments are another step toward unified wireless power, sensing, and communication solutions in the future.
© 2021 IEEE. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. Manuscript received June 26, 2020; revised September 30, 2020; accepted November 2, 2020. Date of publication November 25, 2020; date of current version June 29, 2021. This work was supported in part by Caltech's Space Solar Power Project (SSPP). This article was approved by Associate Editor Pietro Andreani. The authors would like to thank N. Chua, A. Fikes, R. Ghazarian, C. Keller, F. Tebbi, and D. Yue for their assistance with certain aspects of system programming, assembly, and evaluation. They also appreciate helpful comments and discussion by A. Ayling, A. Fikes, B.V Gurses, C. Ives, D. Sarkar, and E. Williams. The authors would also like to acknowledge the original contributions of Prof. K. Sengupta to the concept of RF lensing. They are also indebted to the anonymous reviewers and the associate editor whose thorough and thoughtful feedback noticeably improved this manuscript. The analysis of RF lensing, the multi-element focusing algorithm based on an orthogonal basis, the secondary volumetric refocusing, and pseudo Hadamard matrices were developed by A. Hajimiri. The hardware architecture was conceived and designed by A. Hajimiri, B. Abiri, F. Bohn, and M. Gal-Katziri. The IC was designed by B. Abiri, F. Bohn, and M. Gal-Katziri with input from A. Hajimiri. The RU was designed and implemented by B. Abiri. The emulator was conceived and implemented by A. Hajimiri and M. H. Manohara.
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