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

• US 10,033,424 B2
• Filed: 05/22/2017
• Issued: 07/24/2018
• Est. Priority Date: 03/22/2013
• Status: Active Grant

• Current Assignee: University of Washington
• Original Assignee: University of Washington
• Inventors: Gollakota, Shyamnath, Smith, Joshua R., Liu, Vincent, Parks, Aaron N., Talla, Vamsi
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US15/601,836
• Publication Number:
  US 20170331509A1
• Time in Patent Office: 428 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:

a transceiver comprising;

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

a demodulator coupled to the antenna, the demodulator comprising an averaging circuit configured to average the RF signal across a plurality of samples of the RF signal to generate at least two power levels, the at least two power levels representative of a backscattered RF signal, wherein the demodulator is configured to demodulate the backscattered RF signal into output bits based on the at least two power levels.

2. The system of claim 1, wherein the averaging circuit is configured to identify the at least two average power levels based on the averaging of the RF signal across the plurality of samples of the RF signal.

3. The system of claim 2, wherein the demodulator is configured to decode the at least two power levels into data from the backscattered RF signal.

4. The system of claim 2, wherein to identify the at least two average power levels, the averaging circuit is further configured to implement an envelope detector.

5. The system of claim 1, wherein the transceiver further comprises:

a power harvester circuit that is configured to harvest energy from the RF signal based on a range and broadcast power of the RF signal.

6. The system of claim 5, wherein the transceiver further comprises:

a microcontroller configured to receive harvested power from the power harvester circuit to provide power to the microcontroller.

7. The system of claim 6, wherein the microcontroller is further configured to control output devices based on the output bits, the output devices coupled to the microcontroller.

8. The system of claim 1, wherein the RF signal is a television broadcast signal, a cellular communication signal, a WiFi signal, or combinations thereof.

9. The system of claim 1, wherein the transceiver further comprises:

a transmitter configured to modulate an impedance of the antenna at a frequency different than a frequency of the RF signal to provide a backscattered RF signal.

10. The system of claim 1, wherein the antenna is tuned to receive a subset of the ultra-high frequency (UHF) band.

12. The receiver of claim 1, further comprising:

a threshold circuit configured to provide a threshold signal including an amplitude that is an average of two voltage levels of the at least two voltage levels of the average signal; and

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

11. A receiver comprising:

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

an averaging circuit configured to provide an average signal including at least two voltage levels based on a rolling average over a plurality of samples of the RF signal for a time period associated with a backscatter modulation frequency, the backscatter modulation frequency being a different frequency than a frequency of the RF signal, the at least two voltage levels representative of a backscattered RF signal.

13. The receiver of claim 11, wherein the averaging circuit includes a first resistor-capacitor (RC) circuit, and wherein the threshold circuit comprises a second RC circuit.

14. The receiver of claim 11, wherein the backscattered RF signal modulated at the backscatter modulation frequency.

15. The receiver of claim 11, wherein the time period associated with the backscatter modulation frequency corresponds to time period greater than a time period of the backscatter modulation frequency.

16. A method, comprising:

averaging a radio frequency (RF) signal incident on an antenna across a plurality of samples of the RF signal to generate at least two power levels, the at least two power levels representative of a backscattered RF signal, the backscatter frequency of the backscattered RF signal being a different frequency than a frequency of the RF signal; and

demodulating the backscattered RF signal to generate output bits.

17. The method of claim 16, further comprising:

harvesting energy from the RF signal to power the microcontroller.

18. The method of claim 16, wherein averaging the RF signal across the plurality of samples of the RF signal to generate the at least two power levels comprises calculating a rolling average over a plurality of samples of the RF signal for a time period associated with the backscatter frequency.

19. The method of claim 16, where demodulating the backscattered RF signal to generate output bits comprises:

averaging two power levels of the at least two power levels to generate a threshold signal; and

comparing the at least two power levels to the threshold signal to generate the output bits.

20. The method of claim 16, further comprising:

controlling at least one output device based on the output bits.