BACKGROUND

Some estimates suggest that the number of connected devices worldwide will increase to 50-200 billion by 2020, with global spending reaching 1.7 trillion in that same year. Connected devices are used at multiple levels of society, from a personal level (for example, wearable devices) to a community level (for example, smart cities). In addition, energy consumption demands are increasing exponentially due to the development of processor-heavy applications, higher data communication rates and technologies, and increased usage of multimedia content. On the other hand, battery technology is constrained by limited space and is currently unable to keep up with the expansion of power needs. Replenishment and maintenance of batteries are costly and critical to device performance. Battery-related issues are a main concern in military, consumer, and commercial markets.

Wireless energy transfer is useful for charging rechargeable batteries, such as batteries used in sensors and mobile devices. Commercially available wireless charging systems have limitations such as low charging rates, need for line-of-sight alignment, and close contact with the device to be charged.

SUMMARY OF THE INVENTION

A method and system are provided to transfer energy wirelessly to power devices by employing distributed energy beam forming, ambient RF energy harvesting, or a combination thereof.

In some embodiments, a controllable, programmable distributed wireless radio frequency (RF)-based charging system and method are provided that include and utilize both hardware and software platforms. The hardware platform includes programmable energy transmitters (ETs) and adaptive energy harvesters coupled with energy-receiving target devices. The software platform remotely manages the hardware profiles and resources (e.g., energy waveforms and transmission powers), schedules energy transmissions from the energy transmitters, and commands switching of the ETs between two modes of RF energy transmission for wireless charging and data access point for data communication. This allows the energy transmitters to be configured adaptively based on the ambient energy availability, energy needs and number of energy-requesting target devices in a network. Under the software control, the energy transmitters can cooperatively form focused beams of energy to transmit power to a set of target devices using radio frequencies within, for example, a license-free industrial, scientific and medical (ISM) band. The energy-receiving target devices, such as sensors, Internet of Things (IoT) enabled appliances, and mobile and/or wearable equipment that are coupled with the adaptive energy harvesters, can utilize the energy contained within the transmitted beams, as well as ambient RF sources, for directly powering their operation or for charging a battery and/or capacitor for subsequent use. The coupled software and hardware platforms can flexibly monitor a wide range of areas, build live energy maps, estimate future energy demands, establish energy and data communications with devices, facilitate interoperability among devices, and detect and/or localize new devices within a coverage area.

Other aspects of the method and system include the following:

1. A method for distributed wireless charging, comprising:

in a network comprising at least two spatially distributed energy transmitters, an energy receiving target device, and a controller comprising one or more processors and memory, and machine readable instructions stored in the memory executable by the one or more processors, the steps of:

receiving, at the controller, a communication from the energy receiving target device or from one of the energy transmitters comprising a need for energy by the energy receiving target device; and

transmitting, by the controller to the at least two energy transmitters, instructions for wireless transmission of radio frequency (RF) energy from the at least two energy transmitters to the energy harvesting target device.

2. The method of embodiment 1, further comprising:

transmitting RF energy to form constructive interference at the energy harvesting target device by the at least two energy transmitters; and

converting energy contained in the RF energy into electrical energy by energy harvesting circuitry in the energy harvesting target device for immediate use or for storage.

3. The method of any of embodiments 1-2, wherein each of the energy transmitters is operative to adjust one or more of a frequency, a phase, and a time of transmission of the RF energy to form constructive energy beams at the energy harvesting target device.
4. The method of any of embodiments 1-3, wherein the instructions transmitted by the controller include one or more of a power level to be transmitted, a duration of transmission, an identification of the energy receiving target device, and a schedule of transmission.
5. The method of any of embodiments 1-4, wherein the instructions transmitted by the controller include one or more of switching the energy transmitters on and off, changing a power level transmitted by each of the energy transmitters, and changing a duration of energy transmission of each of the energy transmitters.
6. The method of any of embodiments 1-5, wherein the instructions transmitted by the controller include active data communication protocols, the communications protocols including at least WiFi, ZigBee, and Bluetooth protocols; a role of each energy transmitter, the roles including an energy transfer mode and a data access point communication mode; and a duration of the roles of the energy transmitters.
7. The method of any of embodiments 1-6, further comprising transmitting, from the energy harvesting target device to one or more of the energy transmitters or to the controller, an indication of one or more of an energy discharging rate, an ambient RF energy harvesting rate, or an energy storage level at the energy harvesting target device.
8. The method of any of embodiments 1-7, further comprising transmitting feedback, from the energy harvesting target device to one or more of the energy transmitters, comprising an indication of a received signal strength from the energy transmitters or channel estimations.
9. The method of any of embodiment 8, further comprising, in response to the feedback, iteratively adjusting one or more of frequency, phase, or timing of the RF energy from one or more of the energy transmitters to optimize constructive interference at the energy harvesting target device.
10. The method of any of embodiments 1-9, wherein the energy harvesting target device further harvests RF energy from an ambient RF source.
11. The method of embodiment 10, wherein the ambient RF source is harvested from radio signals, cellular signals, global system for mobile (GSM) signals, or digital or analog television signals.
12. The method of any of embodiments 1-11, wherein the energy receiving target device is one of a set of multiple energy receiving target devices in the network, and the instructions include scheduling transmissions of energy over time to each of the energy receiving target devices.
13. The method of any of embodiments 1-12, wherein the energy receiving target device is one of a set of multiple energy receiving target devices in the network, and the controller is operative to apportion energy transmission between multiple ones of the energy harvesting target devices based on current energy levels of each energy harvesting target device, a number of the energy harvesting target devices, and an estimated future energy demand.
14. The method of any of embodiments 1-13, wherein the energy receiving target device is one of a set of multiple energy receiving target devices in the network, and the controller is operative to register, authenticate or track a location of each of the multiple energy harvesting target devices.
15. The method of any of embodiments 1-14, wherein the energy receiving target device is one of a set of multiple energy receiving target devices in the network, and the controller includes an energy map stored in the memory, the energy map comprising an updatable compilation of present and historical energy levels of the multiple energy harvesting target devices.
16. The method of any of embodiments 1-15, further comprising switching each of the energy transmitters between an energy transmission mode and a data communication mode.
17. The method of any of embodiments 1-16, wherein each of the energy transmitters comprises a software-defined radio configurable by communications from the controller, and an antenna in communication with the software-defined radio.
18. The method of any of embodiments 1-17, wherein one or more of the energy transmitters further comprise a data access point or a gateway for the network.
19. The method of any of embodiments 1-18, wherein the energy harvesting target device is a sensor, an Internet of Things-enabled device or appliance, a mobile device, an air-borne device, a wearable device, an implantable device, or a computing device.
20. The method of any of embodiments 1-19, wherein the energy harvesting target device includes energy harvesting circuitry operative to convert energy contained in RF energy into electrical energy for immediate use or for storage.
21. The method of embodiment 20, wherein the energy harvesting circuitry includes an antenna, a DC voltage rectifier in communication with the antenna, and an energy storage device in communication with the DC voltage rectifier.
22. The method of any of embodiments 20-21, wherein the energy harvesting circuitry includes a stage optimized for high RF to DC conversion efficiency for low input power levels and a stage optimized for high input power levels.
23. The method of any of embodiments 20-22, wherein the energy harvesting circuitry includes impedance matching circuitry to optimize RF to DC conversion efficiency over a desired frequency range.
24. The method of any of embodiments 20-23, wherein the energy storage device comprises a battery or a capacitor.
25. A system for distributed wireless charging, comprising:

a network comprising at least two spatially distributed energy transmitters, an energy receiving target device, and a controller comprising one or more processors and memory, and machine readable instructions stored in the memory executable by the one or more processors, the controller operative to carry out operations comprising:

receiving a communication from at least one energy harvesting target device; and

transmitting to at least two energy transmitters instructions for wireless transmission of radio frequency energy from the at least two energy transmitters to the energy harvesting target device.

26. The system of embodiment 25, wherein the controller is operative to transmit instructions including one or more of a power level to be transmitted, a duration of transmission, an identification of the energy receiving target device, and a schedule of transmission.
27. The system of any of embodiments 25-26, wherein the controller is operative to transmit instructions including one or more of switching the energy transmitters on and off, changing a power level transmitted by each of the energy transmitters, and changing a duration of energy transmission of each of the energy transmitters.
28. The system of any of embodiments 25-27, wherein the controller is operative to transmit instructions including active data communication protocols, the communications protocols including at least WiFi, ZigBee, and Bluetooth protocols; a role of each energy transmitter, the roles including an energy transfer mode and a data access point communication mode; and a duration of the roles of the energy transmitters.
29. The system of any of embodiments 25-28, wherein each of the energy transmitters is operative to adjust one or more of a frequency, a phase, and a time of transmission of the RF energy to form constructive energy beams at the energy harvesting target device.
30. The system of any of embodiments 25-29, wherein each of the energy transmitters comprises a software-defined radio configurable by communications from the controller, and an antenna in communication with the software-defined radio.
31. The system of any of embodiments 25-30, wherein one or more of the energy transmitters further comprise a data access point or a gateway for the network.
32. The system of any of embodiments 25-31, wherein one or more of the energy transmitters is operative to optimize constructive interference at the energy harvesting target device in response to the feedback, by iteratively adjusting one or more of frequency, phase, or timing of the RF energy.
33. The system of any of embodiments 25-32, wherein the energy receiving target device includes energy harvesting circuitry operative to convert energy contained in the RF energy into electrical energy for immediate use or for storage.
34. The system of embodiment 33, wherein the energy harvesting circuitry includes an antenna, a DC voltage rectifier in communication with the antenna, and an energy storage device in communication with the DC voltage rectifier.
35. The system of embodiment 34, wherein the energy storage device comprises a battery or a capacitor.
36. The system of any of embodiments 33-35, wherein the energy harvesting circuitry includes a stage optimized for RF energy conversion efficiency at low input power levels and a stage optimized for RF energy conversion efficiency at high input power levels.
37. The system of any of embodiments 33-36, wherein the energy harvesting circuitry includes impedance matching circuitry to optimize RF energy conversion efficiency over a desired frequency range.
38. The system of any of embodiments 25-37, wherein the energy harvesting target device is operative to further harvest RF energy from an ambient RF source.
39. The system of embodiment 38, wherein the ambient RF source is harvested from radio signals, cellular signals, global system for mobile (GSM) signals, or digital or analog television signals.
40 The system of any of embodiments 25-39, wherein the energy harvesting target device is operative to transmit, to one or more of the energy transmitters or to the controller, an indication of one or more of an energy discharging rate, an ambient RF energy harvesting rate, or an energy storage level at the energy harvesting target device.
41. The system of any of embodiments 25-40, the energy harvesting target device is operative to transmit, to one or more of the energy transmitters, feedback comprising an indication of a received signal strength from the energy transmitters or channel estimations.
42. The system of any of embodiments 25-41, wherein the energy receiving target device is one of a set of multiple energy receiving target devices in the network, and the controller is operative to transmit instructions including scheduling transmissions of energy over time to each of the energy receiving target devices.
43. The system of any of embodiments 25-42, wherein the energy receiving target device is one of a set of multiple energy receiving target devices in the network, and the controller is operative to apportion energy transmission between multiple ones of the energy harvesting target devices based on current energy levels of each energy harvesting target device, a number of the energy harvesting target devices, and an estimated future energy demand.
44. The system of any of embodiments 25-43, wherein the energy receiving target device is one of a set of multiple energy receiving target devices in the network, and the controller is operative to register, authenticate or track a location of each of the multiple energy harvesting target devices.
45. The system of any of embodiments 25-44, wherein the energy receiving target device is one of a set of multiple energy receiving target devices in the network, and the controller includes an energy map stored in the memory, the energy map comprising an updatable compilation of present and historical energy levels of the multiple energy harvesting target devices.
46. The system of any of embodiments 25-45, wherein the energy harvesting target device is a sensor, a sensor mote, an Internet of Things-enabled device or appliance, a mobile device, an air-borne device, a wearable device, an implantable device, or a computing device.
47. A control system for distributed wireless charging, comprising:

a controller comprising one or more processors and memory, and machine-readable instructions stored in the memory that, upon execution by the one or more processors cause the system to carry out operations comprising:

receiving a communication from at least one energy harvesting target device; and

transmitting to at least two energy transmitters instructions for wireless transmission of radio frequency energy from the at least two energy transmitters to the energy harvesting target device.

48. The control system method of embodiment 47, wherein the controller is operative to transmit instructions including one or more of a power level to be transmitted, a duration of transmission, an identification of the energy receiving target device, and a schedule of transmission.
49. The control system any of embodiments 47-48, wherein the controller is operative to transmit instructions including one or more of switching the energy transmitters on and off, changing a power level transmitted by each of the energy transmitters, and changing a duration of energy transmission of each of the energy transmitters.
50. The control system any of embodiments 47-49, wherein the controller is operative to transmit instructions including use of one or more of active data communication protocols, the communications protocols including at least WiFi, ZigBee, and Bluetooth protocols; a role of each energy transmitter, the roles including an energy transfer mode and a data access point communication mode; and a duration of the roles of the energy transmitters.
51. The control system of any of embodiments 47-50, wherein the controller is operative to transmit instructions including scheduling transmissions of energy over time to multiple energy receiving target devices.
52. The control system of any of embodiments 47-51, wherein the controller is operative to transmit instructions to apportion energy transmission between multiple energy harvesting target devices based on current energy levels of each energy harvesting target device, a number of the energy harvesting target devices, and an estimated future energy demand.
53. The control system of any of embodiments 47-52, wherein the controller is operative to register, authenticate or track a location of each of multiple energy harvesting target devices.
54. The control system of any of embodiments 47-53, wherein the controller includes an energy map stored in the memory, the energy map comprising an updatable compilation of present and historical energy levels of multiple energy harvesting target devices.

