Non-Gaussian beamforming for wireless power transfer optimization
System and methods are described herein for providing wireless power to a target device, such as a laptop computer, a mobile phone, a vehicle, robot, or an unmanned aerial vehicle or system (UAV) or (UAS). A tunable multi-element transmitter may transmit electromagnetic radiation (EMR) to the target device using any of a wide variety of frequency bands. A location determination subsystem and/or range determination subsystem may determine a relative location, orientation, and/or rotation of the target device. For a target device within a distance range for which a smallest achievable waist of the Gaussian beam of the EMR at an operational frequency is smaller than the multi-element EMR receiver of the target device, a non-Gaussian beamform may be determined to increase efficiency, decrease overheating, reduce spillover, increase total power output of rectenna receivers on the target device, or achieve another target power delivery goal.
1. A method for providing wireless power to an unmanned aerial vehicle, comprising:
receiving location data of a target device relative to a tunable multi-element transmitter configured to transmit electromagnetic radiation (EMR) to the target device;
determining within which of a first distance range and a second distance range the target device is located from the tunable multi-element transmitter,
wherein the first distance range includes distances at which a smallest achievable waist of a Gaussian beam of the EMR transmitted by the tunable multi-element transmitter is larger than a multi-element EMR receiver of the target device and
wherein the second distance range includes distances at which the smallest achievable waist of the Gaussian beam of the EMR transmitted by the tunable multi-element transmitter is smaller than the multi-element EMR receiver of the target device; and
transmitting EMR from the tunable multi-element transmitter to the multi-element EMR receiver of the target device
(i) using a Gaussian beamform when the target device is determined to be within the first distance range and
(ii) using a non-Gaussian beamform when the target device is determined to be within the second distance range.
2. The method of claim 1 , wherein the target device is determined to be within the second distance range such that transmitting EMR from the tunable multi-element transmitter to the multi-element EMR receiver of the target device comprises transmitting a non-Gaussian beamform.
3. The method of claim 2 , wherein the receiver is divided into a plurality of sub-receivers and a combiner circuit is configured to combine power from each of the sub-receivers.
4. A system to provide wireless power to an unmanned aerial vehicle, comprising:
a tunable multi-element transmitter to transmit electromagnetic radiation (EMR) to a target device
(i) using a Gaussian beamform when the target device is determined to be within a first distance range and
(ii) using a non-Gaussian beamform when the target device is determined to be within a second distance range;
a location determination subsystem to determine a location of the target device relative to the tunable multi-element transmitter, based on received location data; and
a range determination subsystem to determine within which of the first distance range and the second distance range the target device is located relative to the multi-element transmitter,
wherein the first distance range includes distances at which a smallest achievable waist of a Gaussian beam of the EMR transmitted by the tunable multi-element transmitter is larger than a multi-element EMR receiver of the target device and
wherein the second distance range includes distances at which the smallest achievable waist of the Gaussian beam of the EMR transmitted by the tunable multi-element transmitter is smaller than the multi-element EMR receiver of the target device.
5. The system of claim 4 , wherein the target device is an unmanned aerial vehicle (UAV).
6. The system of claim 5 , wherein the receiver comprises a multi-element receive aperture.
7. The system of claim 6 , wherein the multi-element receive aperture comprises a plurality of harvester elements configured to convert EMR to an electric current.
8. The system of claim 4 , further comprising a power monitoring system to receive an indication of a power characteristic of an electric current produced from the EMR received by the receiver of the target device.
9. The system of claim 8 , wherein the indication of the power characteristic comprises a temperature measurement.
10. The system of claim 8 , wherein the indication of the power characteristic comprises a temperature measurement associated with the target device, and wherein the system further comprises an infrared camera to capture the temperature measurement.
11. The system of claim 8 , wherein the power characteristic comprises a voltage characteristic of the electric current.
12. The system of claim 11 , wherein the voltage characteristic comprises a root mean square (RMS) voltage.
13. The system of claim 8 , wherein the power characteristic comprises a current characteristic of the electric current produced from the received EMR by the receiver.
14. The system of claim 4 , wherein the location data comprises data received from a camera viewing the target device.
15. The system of claim 4 , wherein the location data comprises data obtained from images captured by a camera on the target device.
16. The system of claim 4 , wherein the location data comprises data from the target device.
17. The system of claim 16 , wherein the location data is provided by one or more transponders on the target device.
18. The system of claim 17 , wherein the location data is obtained by transmitting a query signal to the target device and receiving a response signal from the one or more transponders on the target device.
19. The system of claim 16 , wherein the location data comprises a relative location and an orientation of the target device.
20. The system of claim 16 , wherein the location determination subsystem is configured to determine a relative location based on a relative time-of-flight measurement of a received signal.
21. The system of claim 16 , wherein the location determination subsystem is configured to determine a relative location based on a time-of-flight measurement of a received signal.
22. The system of claim 16 , wherein the location determination subsystem is configured to determine a relative location based on a phase-offset measurement of a received signal.
23. The system of claim 16 , wherein the location determination subsystem is configured to determine a relative location based on a code phase shift measurement of a received signal.
24. The system of claim 16 , wherein the location determination subsystem is configured to determine a relative location based on a code phase delay measurement of a received signal.
25. The system of claim 16 , wherein the location determination subsystem is configured to determine a relative location based on a frequency-offset measurement of a received signal.
26. The system of claim 16 , wherein the location determination subsystem is configured to determine a relative location based on an angle-of-arrival measurement of a received signal.
27. The system of claim 4 , further comprising a beamform calculator to determine the target, non-Gaussian beamform when the target device is determined within the second distance range.
28. The system of claim 27 , wherein the beamform calculator is configured to determine the target beamform by calculating the target beamform using nonlinear multiple-input-multiple-output (M IMO) techniques.
29. The system of claim 27 , wherein the beamform calculator is configured to determine the target beamform by calculating the target beamform using nonlinear time-reversal beamform calculation techniques.
30. The system of claim 27 , wherein the beamform calculator is configured to determine the target beamform having a non-Gaussian field distribution that approximates a ring-shaped distribution of EMR incident on the receiver of the target device.
31. The system of claim 27 , wherein the beamform calculator is configured to determine the target beamform based on a weighted function of (i) uniformly distributing EMR incident on the receiver and (ii) reducing spillover EMR on the edges of the receiver.