RFID verifier system with grade classification

• US 7,400,989 B2
• Filed: 09/27/2004
• Issued: 07/15/2008
• Est. Priority Date: 09/27/2004
• Status: Active Grant

• Current Assignee: TSC Auto ID Technology Co., Ltd.
• Original Assignee: Printronix
• Inventors: Chiu, Lihu M., Chapman, Theodore A.
• Primary Examiner(s): Barbee; Manuel L.
• Application Number:
  US10/951,573
• Publication Number:
  US 20060068701A1
• Time in Patent Office: 1,387 Days
• Field of Search: 702/58, 702/81
• US Class Current: 702/81
• CPC Class Codes: G01R 31/2822 of microwave or radiofrequency circuits of attenuation, gain, e.g. using network analyzers G01R27/28
• CPC Class Codes: G01R 31/309 of printed or hybrid circuits or circuit substrates
• 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 7/0095 Testing the sensing arrangement, e.g. testing if a magnetic card reader, bar code reader, RFID interrogator or smart card reader functions properly testing of electrical circuits G01R31/28
• CPC Class Codes: G06K 7/10465 the interrogation device being capable of self-diagnosis, e.g. in addition to or as part of the actual interrogation process testing of electrical circuits in general G01R31/28

Abstract

An RFID verifier includes a transmit signal strength indicator (TSSI) and a receive signal strength indicator (RSSI). Using the TSSI, the RFID verifier may determine the amount of power an interrogated RFID tag is illuminated with. Similarly, using the RSSI, the RFID verifier may determine the amount of power returned to the RFID verifier by the RFID tag. By processing the returned power and the illuminating power with a transfer function, the RFID verifier may provide an absolute indicia of quality for the interrogated RFID tag.

Claims

1. An RFID tag verification method, comprising:

determining an optimal location from which an absolute measure of quality may be measured from a first RFID tag;

from a second location;

determining a measure of quality for the first RFID tag to establish a transfer function between the measure of quality at the second location and the absolute measure of quality from the optimal location;

interrogating a second RFID tag with a first interrogating RFID signal;

measuring the power of the interrogating RF signal;

receiving a modulated RF signal from a second interrogated RFID tag;

measuring the power of the received modulated RF signal from the second interrogated RFID tag; and

processing the measured powers from the interrogated second RFID tag with the transfer function to provide an absolute measure of quality for the interrogated second RFID tag.

2. The RFID tag verification method of claim 1, wherein determining a first location from which an absolute measure of quality may be measured from a first RFID tag comprises:

from a plurality of locations, interrogating the first RFID tag with a second interrogating RFID signal, the second interrogating RFID signal having the same power as the first interrogating RFID signal;

at each of the locations in the plurality of locations, receiving a modulated RF signal from a first interrogated RFID tag;

measuring the power of the received modulated RF signal from the first interrogated RFID tag for each of the locations in the plurality;

comparing the measured powers of the received modulated signal from the first interrogated RFID tag to determine the greatest power, wherein the location with the greatest power is the first location.

3. The method of claim 2, further comprising:

classifying the second RFID tag based upon its absolute measure of quality.

4. The method of claim 3, wherein the classification comprises classifying the second RFID tag into either a passing grade or a failing grade.

5. The method of claim 4, wherein the passing grade comprises a plurality of passing grades.

6. The method of claim 3, wherein the classification of the second RFID tag is further based upon additional information.

7. The method of claim 6, wherein the additional information comprises SKU information.

8. A system, comprising:

a bar code label printer; and

an RFID verifier including;

a transceiver operable to interrogate with an interrogating signal an RFID tag and to receive a resulting backscattered signal from the interrogated RFID tag;

a transmit signal strength indicator operable to measure the interrogating signal power;

a received signal strength indicator operable to measure the signal power from the interrogated RFID tag; and

a processor operable to compare the measured interrogating signal power and RFID tag signal power to obtain an measure of quality for the interrogated RFID tag, the processor being configured to classify the measure of quality with reference to a predetermined absolute measure of quality, wherein the interrogated RFID tag is associated with an article, the system being configured to apply a bar code label from the printer to the article if the measure of quality is classified into an acceptable grade of quality.

9. The system of claim 8, wherein the classification of the measure of quality is a function of SKU information from the article.

10. The system of claim 8, wherein the transceiver is a superheterodyne transceiver.

11. The system of claim 8, wherein the transceiver is a homodyne transceiver.

12. An RFID tag verification method, comprising:

determining an optimal location from which an absolute measure of quality may be measured from a first RFID tag;

from a second location;

determining a measure of quality for the first RFID tag to establish a transfer function between the measure of quality at the second location and the absolute measure of quality from the optimal location;

interrogating a second RFID tag with a first interrogating RFID signal;

measuring the power of the interrogating RF signal;

receiving a modulated RF signal from a second interrogated RFID tag;

measuring the power of the received modulated RF signal from the second interrogated RFID tag; and

processing the measured powers from the interrogated second RFID tag with the transfer function to identify an antenna type implemented in the second RFID tag.