RFID verifier

• US 20070013522A1
• Filed: 08/01/2006
• Published: 01/18/2007
• Est. Priority Date: 09/16/2004
• Status: Active Grant

• Current Assignee: Printronix
• Original Assignee: Printronix
• Inventors: Chiu, Lihu
• Granted Patent: US 7,479,883 B2
• Time in Patent Office: Days
• US Class Current: 340/572.100
• CPC Class Codes: G01R 31/2822 of microwave or radiofrequency circuits of attenuation, gain, e.g. using network analyzers G01R27/28
• 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 is configured to vary a slope for a ramp-modulated interrogating signal to determine the slope at which an interrogated RFID tag no longer responds to the interrogating signal. In this fashion, the RFID verifier may obtain a measure of quality for the interrogated RFID tag with respect to the tag'"'"'s ability to decode ramp-modulated signals.

Claims

14. An RFID tag verification method, comprising:

interrogating an RFID tag with an interrogating RF signal;

ramp-modulating the interrogating RF signal; and

varying a slope for the ramp modulation to determine a first measure of quality for the RFID tag.

1. An RFID verifier, comprising:

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

a processor operable to vary a slope of a ramp modulation for the interrogating signal to obtain a first measure of quality for the interrogated RFID tag.

2. The RFID verifier of claim 1, wherein the transceiver is a superheterodyne transceiver.

3. The RFID verifier of claim 1, wherein the transceiver is a homodyne transceiver.

4. The RFID verifier of claim 1, further comprising:

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

a received signal strength indicator operable to measure a power of the backscattered signal;

wherein the processor is further operable to compare the interrogating signal power and power for the backscattered signal to obtain a second measure of quality for the interrogated RFID tag.

5. The RFID verifier of claim 1, further comprising:

a display operable to display an image of the interrogated RFID tag, wherein the RFID verifier is configured such that fiducials on the display guide a user to locate the RFID verifier at a desired range from the interrogated RFID tag.

6. The RFID verifier of claim 5, wherein the RFID verifier is further configured so that the fiducials are oriented within the display such that if the RFID verifier is oriented so that the interrogated RFID tag has a predetermined relationship with the oriented fiducials, the oriented RFID verifier has a predetermined angular orientation with respect to an antenna beam for the interrogated RFID tag.

7. The RFID verifier of claim 6, wherein the oriented RFID verifier is also at a predetermined range from the interrogated RFID tag.

8. The RFID verifier of claim 7, wherein the predetermined relationship of the interrogated RFID tag and the oriented fiducials is that the interrogated RFID tag is centered within the oriented fiducials.

9. The RFID verifier of claim 8, wherein the RFID verifier is further configured so that the fiducials may be oriented within the display at a first orientation and at a second orientation such that if the RFID verifier is first oriented so that the interrogated RFID tag has a predetermined relationship with the first-oriented fiducials, the first-oriented RFID verifier has a first predetermined angular orientation with respect to the antenna beam for the interrogated RFID tag and such that if the RFID verifier is second oriented so that the interrogated RFID tag has a predetermined relationship with the second-oriented fiducials, the second-oriented RFID verifier has a second predetermined angular orientation with respect to the antenna beam for the interrogated RFID tag, the first angular orientation and the second angular orientation being on opposing sides of the antenna beam.

10. The RFID verifier of claim 6, wherein the RFID verifier is further configured to measure the backscattere signal power as the RFID verifier is moved from the first angular orientation to the second angular orientation.

11. The RFID verifier of claim 1, further comprising:

a GPS module operable to determine GPS coordinates of the interrogated RFID tag and the RFID verifier.

12. The RFID verifier of claim 11, wherein the RFID verifier is configured to process the GPS coordinates of the interrogated RFID tag to determine desired GPS coordinates of the RFID verifier such that if the RFID verifier is located at a the desired GPS coordinates, the located RFID verifier is at a desired range from the interrogated RFID tag.

13. The RFID verifier of claim 12, wherein the RFID verifier is further configured to process the GPS coordinates of the interrogated RFID tag to determine the desired GPS coordinates of the RFID verifier such that if the RFID verifier is located at the desired GPS coordinates, the located RFID verifier also has a predetermined angular relationship with respect to an antenna beam for the interrogated RFID tag.

15. The method of claim 14, wherein varying the slope comprises varying the slope until the RFID tag no longer responds to the interrogating RF signal.

16. The method of claim 14, further comprising:

measuring the power of the interrogating RF signal;

receiving a modulated RF signal from the interrogated RFID tag;

measuring the power of the received modulated RF signal; and

comparing the measured powers to provide a second measure of quality for the interrogated RFID tag.

17. The method of claim 16, wherein measuring the power of the received modulated RF signal comprises measuring the power of the received modulated signal at a plurality of locations with respect to an antenna beam for the interrogated RFID tag.

16-1. The method of claim 14, further comprising comparing the measured powers at the plurality of locations to determine an optimal location for an RFID reader.

17-2. The method of claim 16, further comprising:

interrogating a second RFID tag with a second interrogating RF signal from the optimal location;

measuring the power of the second interrogating RF signal;

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

measuring the power of the received second modulated RF signal; and

comparing the measured powers of the received second modulated signal and the second interrogating RF signal to provide a measure of quality for the interrogated second RFID tag.

18. An RFID verifier, comprising:

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

means for measuring the interrogating signal power;

means for measuring the signal power from the interrogated RFID tag;

means for comparing the measured interrogating signal power and RFID tag signal power to obtain a first measure of quality for the interrogated RFID tag; and

means for varying a ramp modulation for the interrogating signal power to obtain a second measure of quality of the interrogated RFID tag.

19. The RFID verifier of claim 18, wherein the transceiver is a superheterodyne transceiver.

20. The RFID verifier of claim 18, wherein the transceiver is a homodyne transceiver.