APPARATUSES, SYSTEMS, AND METHODS FOR COMMUNICATING USING MIMO AND SPREAD SPECTRUM CODING IN BACKSCATTER OF AMBIENT SIGNALS

• US 20180241604A1
• Filed: 04/20/2018
• Published: 08/23/2018
• Est. Priority Date: 02/11/2014
• Status: Active Grant

• Current Assignee: University of Washington
• Original Assignee: University of Washington
• Inventors: Gollakota, Shyamnath, Smith, Joshua R., Parks, Aaron N., Liu, Angli
• Granted Patent: US 10,270,639 B2
• Time in Patent Office: Days
• CPC Class Codes: H04B 1/40 Circuits
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04K 2203/20 for contactless carriers, e.g. RFID carriers record carriers with integrated circuit chips including means for preventing undesired reading or writing from or to record carriers by hindering electromagnetic reading or writing G06K19/07318; arrangements for sensing record carriers including arrangements for protecting the interrogation against piracy attacks G06K7/10257
• CPC Class Codes: H04K 3/25 based on characteristics of target signal or of transmission as countermeasure against surveillance H04K3/827, e.g. using direct sequence spread spectrum or fast frequency hopping spread spectrum techniques H04B1/69

Abstract

Apparatuses, systems, ambient RF backscatter transceivers, and methods for communicating using MIMO and spread spectrum coding of backscattered ambient RF signals are described. An example system may include an ambient RF backscatter transceiver that include an antenna configured to receive a backscattered ambient radio frequency (RF) signal, and a receiver coupled to the antenna. The receiver may be configured to demodulate the backscattered ambient RF signal using one of multiple input, multiple output multiplexing demodulation or spread spectrum code demodulation to retrieve the first data. The backscattered ambient RF signal may be generated by backscattering an ambient RF signal at a first frequency. The ambient RF signal may be configured to provide other data at a second frequency.

Claims

1. An apparatus comprising:

a first antenna configured to receive a first version of a backscattered radio frequency (RF) signal;

a second antenna configured to receive a second version of the backscattered RF signal;

a receiver coupled to the first antenna and the second antenna, wherein the receiver is configured to utilize analog circuitry to perform demodulation of the backscattered RF signal to provide output bits using at least one of;

(1) multiple input, multiple output (MIMO) multiplexing demodulation, or

(2) spread spectrum code demodulation; and

power harvest circuitry configured to harvest power from the RF signal power the demodulation.

2. The apparatus of claim 1, wherein the spread spectrum code demodulation is based on demodulating the backscattered RF signal into a pseudorandom string of bits.

3. The apparatus of claim 2, wherein the power harvest circuitry coupled to the first antenna, the power harvest circuitry further configured to receive the backscattered RF signal from the first antenna.

4. The apparatus of claim 2, further comprising:

a microcontroller coupled to the receiver and configured to decode the output bits to retrieve the data provided by the backscattered RF signal, wherein the power harvest circuitry is further configured to provide the power that was harvested to the microcontroller.

5. The apparatus of claim 2, wherein the receiver comprises:

a first envelope detector circuit configured to filter out transitions of the first version of the backscattered RF signal received at the first antenna to provide a first signal envelope.

6. The apparatus of claim 5, wherein the receiver further comprises:

a code circuit configured to provide a threshold value based on an average of I and Q values of the first signal envelope, the code circuit configured to compute the average of the I and Q values over the chip duration.

7. The apparatus of claim 6, wherein the receiver further comprises:

a threshold circuit configured to provide an output based on a comparison of the threshold value to a rolling average of threshold values provided by the code circuit.

8. The apparatus of claim 6, wherein the code circuit is further configured to demodulate the backscattered RF signal based on an in-phase and quadrature-phase correlation to generate the respective I and Q values.

9. The apparatus of claim 8, wherein the code circuit further comprises a summation circuit configured to add the magnitude of the in-phase component and the magnitude of the quadrature-phase component to generate a sum signal utilized in the average of the I and Q values.

10. The apparatus of claim 6, wherein the power harvest circuitry is further configured to provide the power that was harvested to the code circuit.

11. The apparatus of claim 5, wherein the receiver further comprises:

a second envelope detector circuit configured to filter out transitions of the second version of the backscattered RF signal received at the second antenna to provide a second signal envelope;

a multiple input, multiple output (MIMO) multiplexing demodulation circuit configured to determine a ratio of the first signal envelope to the second signal envelope; and

a threshold circuit configured to provide an output based on a comparison of a threshold value to the ratio of the first signal envelope to the second signal envelope.

12. An apparatus comprising:

an antenna configured to receive a backscattered radio frequency (RF) signal, the backscattered RF signal comprising data encoded using spread spectrum coding; and

a receiver coupled to the antenna, wherein the receiver is configured to demodulate the backscattered RF signal using a spread spectrum code demodulation circuit to provide output bits, wherein the spread spectrum code demodulation circuit comprises analog circuitry configured to discriminate between codes of the spread spectrum coding.

13. The apparatus of claim 12, wherein the spread spectrum code demodulation circuit configured to demodulate the backscattered RF signal based on a sum of a magnitudes of an in-phase component of the backscattered RF signal and a quadrature-phase component of the backscattered RF signal.

14. The apparatus of claim 12, wherein a string of the backscattered RF signal having a first value is alternative ones and zeroes, and another string of the backscattered. RF signal having a second value is all zeroes.

15. The apparatus of claim 12, further comprising:

a microcontroller coupled to the receiver and configured to decode the output bits to retrieve the data.

16. The ambient RF backscatter transceiver of claim 12, wherein the spread spectrum code demodulation circuit further comprises a summation circuit configured to add a magnitude of an in-phase component and a magnitude of a quadrature-phase component to produce a sum signal, wherein the summation circuit comprises:

an amplifier configured to provide the sum signal at an output based on the magnitude of the in-phase component and the magnitude of the quadrature-phase component received at a first input, wherein a second input of the amplifier is coupled to a reference node;

a first resistor configured to provide the magnitude of the in-phase signal to the first input of the amplifier; and

a second resistor configured to provide the magnitude of the quadrature-phase signal to the first input of the amplifier.

17. A method, comprising:

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

demodulating the backscattered ambient RF signal using spread spectrum code demodulation based on a chip duration; and

retrieving the first data based on a demodulated backscattered ambient RF

18. The method of claim 17, wherein, while demodulating the backscattered RF signal using spread spectrum code demodulation, demodulating the ambient backscattered RF signal based on an in-phase and quadrature-phase correlation.

19. The method of claim 18, wherein the backscattered RF signal is modulated at a chip rate and a chip length, wherein a chip of the backscattered RF signal having a first value is alternative ones and zeroes, and a chip of the backscattered ambient RF signal having a second value is all zeroes, the method further comprising:

multiplying the backscattered ambient RF signal at a zero degree reference;

accumulating the multiplied signal at the zero degree reference to generate an in-phase component;

extracting a magnitude of the in-phase component;

multiplying the backscattered ambient RF signal at a ninety degree reference;

accumulating the multiplied signal at the ninety degree reference to generate a quadrature-phase component; and

extracting a magnitude of the quadrature-phase component.

20. The method of claim 19, further comprising adding the magnitude of the in-phase component and the magnitude of the quadrature-phase component to produce a sum signal.