RFID tag distance measurer

Patent metadata

Field	Value
Publication number	US-9442180-B2
Application number	US-201514979205-A
Country	US
Kind code	B2
Filing date	Dec 22, 2015
Priority date	May 23, 2013
Publication date	Sep 13, 2016
Grant date	Sep 13, 2016

Abstract

A radio frequency identification (RFID) tag distance measuring system and method is disclosed. One example includes a first replica path that receives a signal that is simultaneously transmitted to an RFID tag. The first replica path includes a plurality of taps at known distances along the first replica path. Each of the plurality of taps has a first tap input coupled with the first replica path. In addition, an RFID signal receiver receives a return signal from the RFID tag and provides the return signal along a measurement input, wherein each of the plurality of taps have a second tap input coupled with the measurement path. A distance determiner detects at least the first of the plurality of taps to have an output and determine a distance measurement to the RFID tag based thereon.

First claim

We claim:

1. A method for electronically measuring distance to an RFID tag, the method comprising:
transmitting a signal to a radio frequency identification (RFID) tag;
simultaneously transmitting the same signal down a replica path configured with a plurality of comparators;
receiving an RFID tag modified return signal;
transmitting the RFID tag modified return signal to the plurality of comparators;
determining a first activated comparator from the plurality of comparators; and
utilizing a distance along the replica path to the first activated comparator to determine a distance to the RFID tag, wherein the plurality of comparators are located at known distances to provide a pre-defined level of accuracy to the distance being determined.

2. The method of claim 1 further comprising:
utilizing a copper wire as the replica path calibrated to account for a time difference between signal travel speed through the atmosphere and through the copper wire.

3. The method of claim 2 further comprising:
coiling the copper wire to reduce a footprint of the copper wire.

4. The method of claim 1 further comprising:
utilizing a fiber optic cable as the replica path, calibrated to account for a time difference between signal travel speed through the atmosphere and through the fiber optic cable.

5. The method of claim 4 further comprising:
coiling the fiber optic cable to reduce a footprint of the fiber optic cable.

6. The method of claim 1 further comprising:
utilizing silicon as the replica path calibrated to account for a time difference between signal travel speed through the atmosphere and through the silicon.

7. The method of claim 1 wherein the replica path comprises a hybrid cable formed via combination of at least two different materials from the group consisting of: silicon, copper and fiber optic cable; that has been calibrated to account for a time difference between signal travel speed through the atmosphere and the hybrid cable.

8. The method of claim 1 further comprising:
providing at least a second replica path configured with the plurality of comparators at known distances different than the known distances of the plurality of comparators of the replica path; and
selectively transmitting the signal on either the replica path or at least the second replica path coupled with the plurality of comparators.

9. The method of claim 1 further comprising:
providing at least a second replica path configured with the plurality of comparators at known distances different than the known distances of the plurality of comparators of the replica path; and
transmitting the signal down on the replica path and at least the second replica path coupled with the plurality of comparators.

10. The method of claim 1 further comprising:
utilizing a time delay on the signal to generate a time-delayed signal;
transmitting the time-delayed signal down the replica path configured with the plurality of comparators, the time-delayed signal acting as a virtual second replica path;
determining a first activated comparator from the plurality of comparators; and
utilizing a distance along the virtual second replica path to the first activated comparator to determine a distance to the RFID tag.

Assignees

• Trimble Navigation Ltd

Inventors

• Sanders Jeffrey
• Ansell Andrew
• Janky James M

Classifications

• G01S13/75 Primary

  using transponders powered from received waves, e.g. using passive transponders {, or using passive reflectors} · CPC title

• G01S13/74 Primary

  Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems · CPC title

• G01S13/08

  Systems for measuring distance only (indirect measurement G01S13/46) · CPC title

• G01S5/14

  Determining absolute distances from a plurality of spaced points of known location · CPC title

• G01S5/30

  Determining absolute distances from a plurality of spaced points of known location · CPC title