REAL-TIME WIRELESS POWER TRANSFER CONTROL FOR PASSIVE BACKSCATTERING DEVICES

• US 20150091706A1
• Filed: 09/30/2013
• Published: 04/02/2015
• Est. Priority Date: 09/30/2013
• Status: Active Grant

• Current Assignee: Duke University, Ricoh Company Limited
• Original Assignee: Duke University
• Inventors: Chemishkian, Sergey, Reynolds, Matthew S., Arnitz, Daniel
• Granted Patent: US 9,754,139 B2
• Time in Patent Office: Days
• US Class Current: 340/10.34
• CPC Class Codes: G06K 7/10158 methods and means used by the interrogation device for reliably powering the wireless record carriers using an electromagnetic interrogation field
• CPC Class Codes: H02J 50/20 using microwaves or radio frequency waves
• CPC Class Codes: H02J 50/70 involving the reduction of electric, magnetic or electromagnetic leakage fields

Abstract

A method and apparatus is disclosed herein for real-time wireless power transfer control. In one embodiment, a system comprises: an RF-energy harvesting sensor tag operable to generate a first backscatter signal and at least one base station operable to deliver RF power to the sensor tag by emitting a first waveform comprising a plurality of subcarriers, wherein the first backscatter signal is generated by the sensor tag by modulated scattering of the first waveform as incident upon the sensor tag, and further wherein the at least one base station subsequently emits a second waveform determined at least in part by a closed-loop feedback control algorithm responsive to measurements of the first backscatter signal.

Claims

1. A wireless power distribution system comprising:

an RF-energy harvesting sensor tag operable to generate a first backscatter signal; and

at least one base station operable to deliver RF power to the sensor tag by emitting a first waveform comprising a plurality of subcarriers,

wherein the first backscatter signal is generated by the sensor tag by modulated scattering of the first waveform as incident upon the sensor tag,

and further wherein the at least one base station subsequently emits a second waveform determined at least in part by a closed-loop feedback control algorithm responsive to measurements of the first backscatter signal.

2. The wireless power distribution system defined in claim 1 wherein the amplitudes and phases of each of the plurality of subcarriers are selected so as to increase the output of a nonlinear energy harvester collecting energy from the first waveform.

3. The wireless power distribution system defined in claim 1 wherein the second waveform is selected to increase a ratio of harvestable power versus incident power in comparison to the first waveform.

4. The wireless power distribution system defined in claim 1 wherein the measurements comprise amplitude and phase of at least one subcarrier of the backscatter signal.

5. The wireless power distribution system defined in claim 1 wherein the at least one base station selects the second waveform by adjusting the amplitude and phase of the first waveform so that the sensor tag receives a waveform more closely resembling the second waveform in response to the at least one base station transmitting the first waveform.

6. The wireless power distribution system defined in claim 1 wherein the at least one base station selects the second waveform by adjusting the first waveform to compensate for one or more of a group consisting of:

variations in channel gains between the at least one base station and the sensor tag, RF disturbance noise, RF measurement noise, and changing harvested energy targets.

7. The wireless power distribution system defined in claim 1 wherein the at least one base station selects the second waveform by adjusting the first waveform to enforce an incident waveform at the sensor tag.

8. The wireless power distribution system defined in claim 1 wherein at least one of the plurality of sensor tags comprises an RFID tag or an RF energy harvesting sensor node.

9. The wireless power distribution system defined in claim 1 wherein the at least one base station comprises a multi-input multi-output (MIMO) base station.

10. A method for delivering power to an RF-energy harvesting backscatter sensor tag, the method comprising:

transmitting, using a transmitter of a base station, a first waveform;

measuring, using a receiver of the base station, a backscattered signal from the backscatter transponder, the backscattered signal resulting from the sensor tag performing modulated scattering of the first waveform as an incident upon the sensor tag;

computing adjustments to the first waveform based on measurements of the backscattered signal and applying the adjustments to create a second waveform; and

transmitting the second waveform to the sensor tag.

11. The method defined in claim 10 wherein measuring the backscattered waveform comprises measuring amplitudes and phases of subcarriers comprising the backscattered waveform.

12. The method defined in claim 10 wherein the adjustments comprise amplitude and phase adjustments to subcarriers in the first waveform.

13. The method defined in claim 10 further comprising using a feedback closed-loop control algorithm to create the second waveform based on measurements of a backscatter signal.

14. The method defined in claim 10 wherein the amplitudes and phases of each of the plurality of subcarriers of the second waveform are selected so as to increase the output of a nonlinear energy harvester collecting energy from the second waveform.

15. The method defined in claim 10 wherein the second waveform results in an increase of a ratio of harvestable power versus incident power in comparison to the first waveform.

16. The method defined in claim 10 wherein adjusting the first waveform to create the second waveform enables the sensor tag to receive through a communication channel a waveform more closely resembling the first waveform in response to transmitting the second waveform.

17. The method defined in claim 10 wherein the first waveform is adjusted to compensate for one or more of a group consisting of:

variations in channel gains between the at least one base station and the sensor tag, RF disturbance noise, RF measurement noise, and changing harvesting energy targets.

18. The method defined in claim 10 wherein the first waveform is adjusted to create the second waveform to enforce an incident waveform at the sensor tag in response to transmitting the second waveform.

19. An article of manufacture having one or more recordable media storing instructions thereon which when executed by a system cause the system to perform a method for delivering power to an RF-energy harvesting backscatter sensor tag, the method comprising:

transmitting, using a transmitter of a base station, a first waveform;

measuring, using a receiver of the base station, a backscattered signal from the backscatter transponder, the backscattered signal resulting from the sensor tag performing modulated scattering of the first waveform as an incident upon the sensor tag;

computing adjustments to the first waveform based on measurements of the backscattered signal and applying the adjustments to create a second waveform; and

transmitting the second waveform to the sensor tag.

20. The article of manufacture defined in claim 19 wherein adjusting the first waveform to create the second waveform enable the sensor tag to receive a waveform more closely resembling the first waveform in response to transmitting the second waveform.

21. A base station for use in a communication system having at least one RF harvesting backscatter sensor tag, the base station comprising:

a transmitter to transmit a first waveform and a second waveform;

a receiver to receive a backscattered signal from the tag, the backscattered signal resulting from the sensor tag performing modulated scattering of the first waveform;

a measurement unit coupled to the receiver to measure the backscattered waveform signal;

a memory coupled to the measurement unit to store the measurements; and

a controller, coupled to the memory, the transmitter, the receiver and the measurement unit, to compute adjustments to the first waveform based on the measurements of the backscattered signal and to cause the transmitter to transmit the second waveform to the sensor tag, the second waveform representing the first waveform with the adjustments the adjustments applied thereto.