1 research outputs found
Retrodirective Antenna Array Approach to Achieve Maximum Theoretical Beam Efficiency in Microwave Wireless Power Transfer
Efficient long range wireless power transfer (WPT) is realized if the
distance between the source and receiver is less than the Fraunhoffer distance.
This distance increases proportionally to the square root of the antenna size
so to achieve efficient long range WPT, larger antennas are mandatory, but that
comes with difficulty in implementing both the feeding network and beamforming
control of the antenna. Several proposed implementations require power-hungry
processors rendering implementation impractical. An alternative to reduce usage
of digital processing is in the form of retrodirective antenna arrays. Its core
operation is to track an incoming signal's direction of arrival and resend it
to the same direction. This can be implemented by analog circuits.
Retrodirective capability on both the generator and rectenna arrays creates a
feedback loop that produces a high efficiency WPT channel. In this paper, we
characterize the dynamics of this phenomenon using a discrete-time state-space
model based on S-parameters and show that the system can naturally achieve
maximum theoretical WPT efficiency. We further confirmed the theoretical
analysis through a hardware experiment using a 12-port circuit board with
measurable S-parameters mimicking a deterministic wireless channel. The results
of the hardware experiment show agreement with the proposed theoretical
framework.Comment: This work has been submitted to the IEEE for possible publication.
Copyright may be transferred without notice, after which this version may no
longer be accessible. 9 pages, 11 figures, 1 table, submitted to the IEEE
Transactions on Theory and Techniques on September 22, 202