Systems and methods for RFID positioning

Patent metadata

Field	Value
Publication number	US-12045681-B2
Application number	US-202318378483-A
Country	US
Kind code	B2
Filing date	Oct 10, 2023
Priority date	Feb 12, 2021
Publication date	Jul 23, 2024
Grant date	Jul 23, 2024

Abstract

Systems and methods for radiolocation using backscatter RFID tags and a special-purpose reader that produces a SFCW RF interrogation signal comprising N carrier frequencies. A backscattered interrogation signal from a backscatter RFID tag is down-converted using at least a portion of the generated SFCW RF interrogation signal. RSP corresponding to the N carrier frequencies are determined. RSS may be determined to improve performance. A distance between the RFID reader and the backscatter RFID tag may be estimated based on at least a summation of differences between RSPs corresponding to adjacent carrier frequencies.

First claim

What is claimed is:

1. A method comprising:
generating, by a signal generator of a radio frequency identification (RFID) reader, a stepped-frequency continuous wave (SFCW) radio frequency (RF) interrogation signal comprising N carrier frequencies;
splitting off at least a portion of the generated SFCW RF interrogation signal and routing the generated SFCW RF interrogation signal to a local down converter;
transmitting at least a portion of the generated SFCW RF interrogation signal by a transmitting (Tx) antenna of the RFID reader;
receiving, by a receiving (Rx) antenna of the RFID reader and in response to the transmitting, a backscattered signal from one or more backscatter RFID tags;
down-converting the received backscattered signal using at least a portion of the generated SFCW RF interrogation signal;
determining, from the down-converted signal, received signal phases (RSPs) corresponding to the N carrier frequencies; and
estimating a distance between the RFID reader and one or more of the backscatter RFID tags based on a summation of differences between RSPs corresponding to adjacent carrier frequencies;
wherein:
determining the RSPs corresponds to the N carrier frequencies and a received signal strength (RSS) from the down-converted signal; and
the method further comprises determining a delay profile using both a normalized complex received signal from the down-converted signal and an un-normalized complex received signal from the down-converted signal.

2. The method of claim 1 further comprising:
estimating an improved distance measurement between the RFID reader and one or more of the backscatter RFID tags based on the delay profile; and
outputting the improved estimate of the distance measurement.

3. The method of claim 2 further comprising:
determining the normalized complex received signal from the down-converted signal; and
determining the un-normalized complex received signal from the down-converted signal.

4. The method of claim 1 , wherein the backscattered signal received from one or more of the backscatter RFID tags comprises a version of the SFCW RF interrogation signal that is modulated and backscattered by one or more of the backscatter RFID tags.

5. The method of claim 1 , wherein the down-converting is performed by a local down-converter of the RFID reader; and
wherein the local down-converter is configured to output an in-phase (I) output and quadrature (Q) output corresponding to the backscattered signal.

6. The method of claim 1 , wherein the SFCW RF interrogation signal is characterized by a sequence of stepped frequencies in a 5.8 GHz industrial, scientific, and medical (ISM) band; and
wherein each of the stepped frequencies are characterized by a dwell time.

7. The method of claim 1 further comprising utilizing three or more RFID readers to triangulate a location of one or more of the backscatter RFID tags.

8. The method of claim 1 , wherein the receiving comprises receiving, by the (Rx) antenna of the RFID reader, and in response to the transmitting, backscattered signals from a plurality of backscatter RFID tags and estimating a distance between the RFID reader and the plurality of backscatter RFID tags.

9. The method of claim 1 further comprising sensing one or more structures between the RFID reader and one or more of the backscatter RFID tags based on delayed or multipath components of the backscattered signal.

10. The method of claim 1 further comprising:
determining the normalized complex received signal from the down-converted signal;
determining the un-normalized complex received signal from the down-converted signal;
estimating an improved distance measurement between the RFID reader and one or more of the backscatter RFID tags based on the delay profile; and
outputting the improved estimate of the distance measurement.

11. The method of claim 10 , wherein the backscattered signal received from one or more of the backscatter RFID tags comprises a version of the SFCW RF interrogation signal that is modulated and backscattered by one or more of the backscatter RFID tags;
wherein the down-converting is performed by a local down-converter of the RFID reader; and
wherein the local down-converter is configured to output an in-phase (I) output and quadrature (Q) output corresponding to the backscattered signal.

12. The method of claim 11 , wherein the SFCW RF interrogation signal is characterized by a sequence of stepped frequencies in a 5.8 GHz industrial, scientific, and medical (ISM) band; and
wherein each of the stepped frequencies are characterized by a dwell time.

13. A radio frequency identification (RFID) radiolocation system comprising:
a signal generator configured to output a stepped-frequency continuous wave (SFCW) radio frequency (RF) interrogation signal comprising N carrier frequencies;
a transmitting (Tx) antenna;
a receiving (Rx) antenna configured to receive a backscattered signal from one or more backscatter RFID tags;
a down-converter configured to output a down-converted signal comprising an in-phase (I) output and a quadrature-phase (Q) output;
a splitter in communication with the signal generator, the Tx antenna, and the down-converter, wherein the splitter is configured to send:
a first portion of the SFCW RF interrogation signal to the Tx antenna; and
a second portion of the SFCW RF interrogation signal to the down-converter;

a software-defined radio configured to digitize and filter the down-converted signal from the down-converter; and
one or more processors in communication with the software-defined radio, one or more of the processors configured to:
determine, from the down-converted signal, received signal phases (RSPs) corresponding to the N carrier frequencies;
estimate a distance between the RFID radiolocation system and one or more of the backscatter RFID tags based on a summation of differences between RSPs corresponding to adjacent carrier frequencies; and
output the estimate of the distance;

wherein:
one or more of the backscatter RFID tags comprise a quantum tunneling tag (QTT);
determining the RSPs corresponds to the N carrier frequencies and a received signal strength (RSS) from the down-converted signal; and
one or more of the processors are further configured to:
determine a normalized complex received signal from the down-converted signal;
determine an un-normalized complex received signal from the down-converted signal;
determine a delay profile using both the normalized complex received signal and the un-normalized complex received signal;
estimate an improved distance measurement between the RFID radiolocation system and one or more of the backscatter RFID tags based on the delay profile; and
output the improved estimate of the distance measurement.

14. The system of claim 13 , wherein one or more of the processors are further configured to determine the RSS from the down-converted signal.

15. The system of claim 13 , wherein the backscattered signal received from one or more of the backscatter RFID tags comprises a version of the SFCW RF interrogation signal that is modulated and backscattered by one or more of the backscatter RFID tags.

16. The system of claim 13 , wherein the SFCW RF interrogation signal is characterized by a sequence of stepped frequencies in a 5.8 GHz ISM band; and
wherein each of the stepped frequencies are characterized by a dwell time.

17. The system of claim 13 further comprising one or more amplifiers.

18. A system comprising:
three or more radiolocation systems, each compri

Assignees

• Georgia Tech Res Inst
• Univ Of Rome Tor Vergata

Inventors

• Qi Cheng
• Amato Francesco
• Durgin Gregory David

Classifications

• G01S13/536

  using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves · CPC title

• G01S7/414

  Discriminating targets with respect to background clutter · CPC title

• G06K7/10118

  the sensing being preceded by at least one preliminary step · CPC title

• G06K7/10009

  sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves · CPC title

• G06K7/10099

  the directional field being used for pinpointing the location of the record carrier, e.g. for finding or locating an RFID tag amongst a plurality of RFID tags, each RFID tag being associated with an object, e.g. for physically locating the RFID tagged object in a warehouse · CPC title