Ambient backscatter tranceivers, apparatuses, systems, and methods for communicating using backscatter of ambient RF signals

• US 9,680,520 B2
• Filed: 07/09/2015
• Issued: 06/13/2017
• Est. Priority Date: 03/22/2013
• Status: Active Grant

• Current Assignee: University of Washington
• Original Assignee: University of Washington
• Inventors: Gollakota, Shyamnath, Liu, Vincent, Parks, Aaron N., Talla, Vamsi, Smith, Joshua R.
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US14/795,719
• Publication Number:
  US 20150311944A1
• Time in Patent Office: 705 Days
• CPC Class Codes: H04B 1/40 Circuits

Abstract

Apparatuses, systems, ambient backscatter transceivers, and methods for modulating a backscatter of an ambient RF signal are described. An example system may include an ambient backscatter transceiver comprising an antenna that is configured to receive a backscattered ambient radio frequency (RF) signal. The ambient backscatter transceiver is configured to demodulate the backscattered ambient RF signal to retrieve first data. The backscattered ambient RF signal is generated by backscattering an ambient RF signal at a first frequency. The ambient RF signal is encoded with modulated to provide second data at a second frequency.

Claims

1. A system comprising:

an ambient backscatter transceiver comprising;

an antenna configured to receive a backscattered ambient radio frequency (RF) signal;

a demodulator coupled to the antenna, the demodulator comprising an averaging circuit configured to reduce variations in the backscattered ambient RF signal, wherein the demodulator is configured to demodulate the backscattered ambient RF signal in part using the averaging circuit to retrieve first data,

wherein the backscattered ambient RF signal is generated by backscattering an ambient RF signal at a first frequency, the ambient RF signal configured to provide second data at a second frequency; and

a transmitter configured to modulate an impedance of the antenna at the first frequency to provide a second backscattered ambient RF signal encoded with another data for transmission to a second ambient backscatter transceiver.

2. The system of claim 1, wherein the ambient backscatter transceiver is a first ambient backscatter transceiver of a plurality of ambient backscatter transceivers, the system further comprising a second ambient backscatter transceiver of the plurality of ambient backscatter transceivers, configured to transmit the first data in the backscattered ambient RF signal by modulating a backscatter of the ambient RF signal at the first frequency.

3. The system of claim 2, wherein the first ambient backscatter transceiver is further configured to transmit third data in a second backscattered ambient RF signal by modulating a backscatter of the ambient RF signal at the first frequency.

4. The system of claim 3, wherein each of the plurality of ambient backscatter transceivers comprises an antenna that is configured to receive the backscattered ambient RF signal and to demodulate the backscattered ambient RF signal to retrieve first data.

5. The system of claim 1, wherein the plurality of ambient backscatter transceivers comprises a respective power harvest circuit that is configured to harvest energy from the ambient RF signal that is used to power the plurality of ambient backscatter transceivers.

6. The system of claim 1, wherein the ambient RF signal is a television broadcast signal, a cellular communication signal, or a WiFi signal.

7. An ambient backscatter transceiver comprising:

an antenna configured to receive a backscattered ambient radio frequency (RF) signal, the backscattered ambient RF signal encoded with first data via backscatter modulation of an ambient RF signal at a first frequency, the ambient RF signal modulated to provide second data at a second frequency;

a receiver coupled to the antenna and configured to demodulate the backscattered ambient RF signal to generate output bits, the receiver comprising an averaging circuit configured to reduce variations in the backscattered ambient RF signal;

a microcontroller coupled to the receiver and configured to decode, at least in part using the averaging circuit, the output bits to retrieve data that is transmitted via the backscattered ambient RF signal; and

a transmitter configured to modulate an impedance of the antenna at the first frequency to provide a second backscattered ambient RF signal encoded with another data for transmission to a second ambient backscatter transceiver.

8. The ambient backscatter transceiver of claim 7, further comprising an output device that is controlled by the microcontroller based on the retrieved data.

9. The ambient backscatter transceiver of claim 7, wherein the transmitter comprises a switching device, wherein the switching device is controlled by the microcontroller.

10. The ambient backscatter transceiver of claim 7, wherein the transmitter is further configured to modulate an impedance of the antenna to backscatter the ambient RF signal to provide a preamble and a header prior to providing the other data.

11. The ambient backscatter transceiver of claim 7, wherein the ambient backscatter transceiver comprises a power harvester configured to harvest energy from the ambient RF signal to power the microcontroller.

12. The ambient backscatter transceiver of claim 7, wherein the receiver comprises:

an averaging circuit configured to provide an average signal having an amplitude that is based on a rolling average of the backscattered ambient RF signal over a time period that is between a time period of the second frequency and the first frequency;

a threshold circuit configured to provide a threshold signal having an amplitude that is based on a rolling average over a time period that is greater than the time period of the first frequency; and

a comparator that is configured to provide output bits based on a comparison of the average signal and the threshold signal.

13. The ambient backscatter transceiver of claim 12, wherein the averaging circuit includes a first resistor-capacitor (RC) circuit, and wherein the threshold circuit comprises a second RC circuit.

14. A method, comprising:

receiving a backscattered ambient radio frequency (RF) signal at an antenna, the backscattered ambient RF signal encoded with first data via backscatter modulation of an ambient RF signal at a first frequency, the ambient RF signal modulated to provide second data at a second frequency;

demodulating the backscattered ambient RF signal to generate output bits, wherein demodulating the backscattered ambient RF signal comprises using an averaging circuit configured to reduce variations in the backscattered ambient RF signal;

decoding the output bits at a microcontroller to retrieve the first data;

receiving the ambient RF signal; and

modulating a backscatter of the ambient RF signal at the first frequency via the antenna to provide a second backscattered ambient RF signal encoded with another data for transmission to an ambient backscatter transceiver.

15. The method of claim 14, further comprising:

receiving the ambient RF signal; and

harvesting energy from the ambient RF signal to power the microcontroller.

16. The method of claim 14, wherein modulating the backscatter of the ambient RF signal via the antenna to provide the second backscattered ambient RF signal encoded with the other data comprises modulating the impedance of the antenna.

17. The method of claim 14, further comprising, prior to modulating the backscatter of the ambient RF signal via the antenna to provide the second backscattered ambient RF signal encoded with the other data, detecting whether another backscattered ambient RF signal is being transmitted.

18. The method of claim 17, wherein detecting whether the other backscattered ambient RF signal is being transmitted comprises detecting alternating reflections and non-reflections of the backscattered ambient RF signal.

19. The method of claim 14, further comprising receiving sensor data from a sensor, wherein the other data is based on the sensor data.

20. The method of claim 14, wherein the backscattered ambient RF signal is modulated according to a bi-phase modulation.

21. The method of claim 14, wherein the first frequency is greater than the second frequency.

22. An ambient backscatter transceiver comprising:

an antenna configured to receive a backscattered ambient radio frequency (RF) signal, the backscattered ambient RF signal encoded with first data via backscatter modulation of an ambient RF signal at a first frequency, the ambient RF signal modulated to provide second data at a second frequency; and

a receiver coupled to the antenna and configured to demodulate the backscattered ambient RF signal to generate output bits, wherein the receiver comprises;

an averaging circuit configured to provide an average signal having an amplitude that is based on a rolling average of the backscattered ambient RF signal over a time period that is between a time period of the second frequency and the first frequency;

a threshold circuit configured to provide a threshold signal having an amplitude that is based on a rolling average over a time period that is greater than the time period of the first frequency;

a comparator that is configured to provide output bits based on a comparison of the average signal and the threshold signal; and

a microcontroller coupled to the receiver and configured to decode the output bits to retrieve data that is transmitted via the backscattered ambient RF signal.

23. The ambient backscatter transceiver of claim 22, wherein the averaging circuit includes a first resistor-capacitor (RC) circuit, and wherein the threshold circuit comprises a second RC circuit.