METHOD AND APPARATUS FOR IMPROVING RECEPTION OF AN RFID TAG RESPONSE

• US 20140035731A1
• Filed: 07/31/2012
• Published: 02/06/2014
• Est. Priority Date: 07/31/2012
• Status: Active Grant

• Current Assignee: Symbol Technologies, LLC (Zebra Technologies Corporation)
• Original Assignee: Motorola Solutions, Inc.
• Inventors: CHAN, Yiu Kwong, SHACHER, Aviv
• Granted Patent: US 9,000,894 B2
• Time in Patent Office: Days
• US Class Current: 340/10.3
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas

Abstract

A method and apparatus for improving reception of responsive RFID signals is provided. The method includes transmitting a plurality of interrogation signals each having a different polarization to activate one or more RFID tags. Responsive signals from the RFID tags are analyzed for receive symbol quality data to select a transmit polarization subset. These polarizations are then used for transmitting further interrogation signals to the RFID tags. The apparatus includes a dual element orthogonal radiator coupled to a transmitter and receiver. A processor controls the transmitter and receiver to transmit a series of RFID interrogation signals each having a different polarization, and receive a series of responsive signals from one or more RFID tags. The responsive signals are analyzed to select a particular a transmit polarization subset that will improve reception of future responsive signals from the RFID tags.

Claims

1. A method comprising:

transmitting a plurality of interrogation signals to activate one or more RFID tags, each of the plurality of interrogation signals being transmitted with a different polarization;

receiving a plurality of responsive signals from the one or more RFID tags;

analyzing receive symbol quality data for each of the plurality of responsive signals using quality parameters to select a transmit polarization subset;

transmitting further interrogation signals to the one or more RFID tags using the a transmit polarization subset.

2. The method of claim 1, wherein transmitting the plurality of interrogation signals further comprises determining a beginning polarization, an end polarization and a polarization step size for transmitting a plurality of interrogation signals.

3. The method of claim 2, which includes periodically repeating the method to update the transmit polarization subset.

4. The method of claim 3, wherein periodically repeating the method comprises repeating the method on one or more of the following group of periodic schedules:

hour, shift, day, week or month.

5. The method of claim 2, which includes repeating the method to update the transmit polarization subset when the receive symbol quality data falls below a threshold.

6. The method of claim 5, wherein the threshold is based upon one or more of the following group of quality parameters:

bit error rate, packet error rate, total data errors, RFID tag read rate or RFID tag capture rate.

7. The method of claim 1, wherein transmitting the plurality of interrogation signals each having a different polarization further comprises varying a magnitude of orthogonally phased interrogation signal components to produce a transmitted interrogation signal having a selected polarization.

8. The method of claim 1, wherein the a transmit polarization subset results in the further interrogation signals arriving at the one or more RFID tags at a substantially linear polarization with respect to the one or more RFID tags.

9. A method comprising:

transmitting a plurality of interrogation signals to activate one or more RFID tags, each of the plurality of interrogation signals being transmitted with a different polarization;

receiving a plurality of responsive signals from the one or more RFID tags;

analyzing receive symbol quality data for each of the plurality of responsive signals using quality parameters to exclude certain polarizations to provide a transmit polarization subset;

transmitting further interrogation signals to the one or more RFID tags using the a transmit polarization subset.

10. The method of claim 9, wherein transmitting the plurality of interrogation signals further comprises determining a beginning polarization, an end polarization and a polarization step size for transmitting a plurality of interrogation signals.

11. The method of claim 10, which includes periodically repeating the method to update the transmit polarization subset.

12. The method of claim 11, wherein periodically repeating the method comprises repeating the method on one or more of the following group of periodic schedules:

hour, shift, day, week or month.

13. The method of claim 11, which includes repeating the method when the receive symbol quality data triggers updating the transmit polarization subset.

14. The method of claim 13, wherein the trigger for updating is based upon one or more of the following group of quality parameters:

bit error rate, packet error rate, total data errors, RFID tag read rate or RFID tag capture rate.

15. The method of claim 9, wherein transmitting the plurality of interrogation signals each having a different polarization further comprises varying a magnitude of orthogonally phased interrogation signal components to produce a transmitted interrogation signal having a selected polarization.

16. A system comprising:

an antenna system having a first antenna element with a first polarization and a second antenna element having a second polarization being orthogonal to the first polarization;

a transmitter coupled to the antenna system;

a receiver coupled to the antenna system;

a processor coupled to the transmitter and receiver and programmed to;

control the transmitter to transmit a series of RFID interrogation signals to one or more RFID tags, each of the series of RFID interrogation signals having a varied transmit polarization;

control the receiver to receive a series of responsive signals from the one or more RFID tags;

analyze receive symbol quality data for each of the series of responsive signals using quality parameters to select a transmit polarization subset; and

transmit further interrogation signals to the one or more RFID tags using the transmit polarization subset.

17. The system of claim 16, wherein the processor is further programmed to periodically re-transmit the series of RFID interrogation signals.

18. The system of claim 17, wherein the processor is further programmed to periodically re-transmit the series of RFID interrogation signals using one or more of the following group of periodic schedules:

hour;

shift;

day;

week;

month.

19. The system of claim 16, wherein the processor is further programmed to analyze receive quality data using one or more of the following group of quality parameters for each of the series of responsive signals:

bit error rate;

package error rate;

total data errors;

RFID tag read rate;

RFID tag capture rate.

20. The system of claim 16, wherein the processor is further programmed select the transmit polarization subset such that transmission of the further interrogation signals results in the further interrogation signals arriving at the one or more RFID tags at a substantially linear polarization with respect to the one or more RFID tags.