Method and apparatus for RFID communication

• US RE43,918 E1
• Filed: 09/28/2007
• Issued: 01/08/2013
• Est. Priority Date: 11/20/1992
• Status: Expired due to Term

• Current Assignee: Round Rock Research LLC
• Original Assignee: Round Rock Research LLC
• Inventors: Tuttle, Mark E., Lake, Rickie C., Schicht, Steven F., Tuttle, John R.
• Primary Examiner(s): CHU, GABRIEL L
• Application Number:
  US11/864,718
• Time in Patent Office: 1,929 Days
• Field of Search: None
• US Class Current: 714/25
• CPC Class Codes: G01R 31/01 Subjecting similar articles in turn to test, e.g. "go/no-go" tests in mass production; Testing objects at points as they pass through a testing station testing of cables continuously passing the testing apparatus G01R31/59; testing dielectric strength or breakdown voltage G01R31/12
• 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 31/3025 Wireless interface with the DUT
• CPC Class Codes: G01R 31/303 of integrated circuits G01R31/305 - G01R31/315 take precedence
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• 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

Abstract

A plurality of battery-operated transceivers encapsulated by lamination to form a sheet of independent transceivers is tested in a two piece fixture that forms an enclosure surrounding each in-sheet transceiver. Each enclosure has an antenna for transmitting a command signal to the transceiver at a known power level and for receiving a reply message from the transceiver containing a power level measurement made by the transceiver. Test methods using the fixture of the present invention are also described.An RFID tag and interrogator may each include a transmitter and a receiver. The tag and interrogator may communicate with each other at different frequency bands and may communicate in accordance with a wireless communication protocol.

Claims

1. A method of testing the RF communication operation of an RF transponder, comprising the steps of:

providing a sheet characterized by first and second opposite faces and a thickness;

mounting on the sheet an RF transponder that includes a transponder RF antenna;

positioning a first RF shield so as to abut the first face of the sheet;

positioning a second RF shield so as to abut the second face of the sheet, the second RF shield being in the shape of a cup having a mouth abutting said second face, wherein the first and second RF shields are positioned so that the first and second RF shields together form a closed cavity which completely surrounds and encloses the transponder RF antenna except where the thickness of the sheet separates the first RF shield from the mouth of the second RF shield, wherein said thickness is sufficiently small so that the first and second RF shields prevent any RF signals within the cavity from radiating outside the cavity;

positioning a test fixture RF antenna within the cavity;

transmitting an RF signal from the test fixture antenna;

detecting a response by the transponder to the RF signal; and

subsequently removing the transponder from proximity to the first and second shields and the test fixture RF antenna, so that no shielding obstructs the transponder RF antenna from sending and receiving RF radiation at any angle.

2. A method according to claim 1, wherein the cavity encloses the entire RF transponder.

3. A method according to claim 1, wherein the sheet has no shielding mounted thereon that obstructs RF radiation from the transponder RF antenna.

4. A method according to claim 1, wherein:

the first RF shield is in the shape of a cup having a mouth abutting the first face; and

the step of positioning the second RF shield further comprises aligning the mouth of the second shield with the mouth of the first shield.

5. A method according to claim 1, wherein the step of positioning the test fixture RF antenna within the cavity comprises:

mounting the test fixture RF antenna to a surface of one of the two RF shields;

connecting an RF transmission line to the test fixture RF antenna; and

passing the transmission line through an opening in said one RF shield to extend outside the cavity.

6. A method according to claim 1, further comprising the step of:

fabricating the sheet to include electrically conductive material adjacent the mouth of the second RF shield so as to improve RF shielding of the cavity.

7. A method according to claim 1, wherein the RF signal is transmitted at a predetermined wavelength, and wherein the RF shields are dimensioned to improve the gain of the cavity at that wavelength.

8. A method according to claim 1, wherein the RF signal is transmitted at a predetermined wavelength, and wherein the RF shields are dimensioned so that the cavity resonates at that wavelength.

9. A method of testing the RF communication operation of a plurality of RF transponders, comprising the steps of:

providing a sheet characterized by first and second opposite faces and a thickness;

mounting on the sheet a plurality of RF transponders, wherein each transponder includes a transponder RF antenna;

positioning a first test fixture section having a first RF shield so that the first RF shield abuts the first face of the sheet;

positioning a second test fixture section so as to abut the second face of the sheet, wherein;

the second test fixture section includes a plurality of RF shields,

each RF shield in the second test fixture section is in the shape of a cup having a mouth abutting said second face of the sheet,

the first and second test fixture sections so that each RF shield in the second test fixture section encircles a corresponding one of the transponder RF antennas so as to form, in combination with the first RF shield, a closed cavity that completely surrounds and encloses said corresponding transponder RF antenna except where the thickness of the sheet separates the first RF shield from the mouth of said RF shield in the second test fixture section, and

said thickness is sufficiently small so that the first and second RF shields prevent any RF signals within the cavity from radiating outside the cavity;

positioning within each cavity a corresponding test fixture RF antenna;

transmitting an RF signal from each test fixture antenna;

detecting a response by each transponder to the RF signal transmitted by its corresponding test fixture antenna; and

subsequently removing each transponder from proximity to the first and second test fixture sections and the test fixture RF antennas, so that no shielding obstructs each transponder RF antenna from sending and receiving RF radiation at any angle.

10. A method according to claim 9, wherein the each cavity encloses the entire corresponding RF transponder.

11. A method according to claim 9, wherein:

the first RF shield is in the shape of a plurality of cups so that each cup has a mouth abutting the first face of the sheet; and

the step of positioning the second RF shield further comprises aligning each mouth of the second shield with a corresponding mouth of the first shield.

12. A test fixture for testing the RF communication operation of an RF transponder which is mounted on a sheet which extends beyond the perimeter of the transponder, the RF transponder having an antenna for receiving RF signals, comprising:

first and second RF shields, the second RF shield being in the shape of a cup having a mouth;

an alignment mechanism for positioning the first and second RF shields to abut opposite sides of the sheet so that the mouth encircles the transponder antenna and so that the combination of the first and second RF shields forms a closed cavity completely surrounding and enclosing the transponder antenna except where the sheet separates the two RF shields, wherein the distance by which the sheet separates the two RF shields is small enough to prevent any RF signals within the cavity from radiating outside the cavity; and

a test fixture RF antenna mounted within the cavity.

13. A test fixture according to claim 12, further comprising:

a test fixture RF transmitter having an output connected to the test fixture RF antenna so that the RF antenna radiates RF signals to the transponder RF antenna; and

a test fixture RF receiver having an input connected to the test fixture RF antenna so that the RF receiver receives any responses transmitted by the RF transponder in response to said RF signals.

14. A test fixture according to claim 12, wherein the cavity encloses the entire transponder.

15. A test fixture according to claim 12, wherein:

the first RF shield is in the shape of a cup having a mouth abutting the first face; and

the alignment mechanism aligns the mouth of the second shield with the mouth of the first shield.

16. A method according to claim 12, further comprising:

an RF transmission line connected to the test fixture RF antenna;

wherein the transmission line extends through an opening in one of the RF shields so as to extend outside the cavity.

17. A test fixture according to claim 12, further comprising a test fixture RF transmitter for providing to the transponder antenna RF test signals having a predetermined wavelength, wherein the first and second RF shields are dimensioned to improve the gain of the cavity at that wavelength.

18. A test fixture according to claim 12, further comprising a test fixture RF transmitter for providing to the transponder antenna RF test signals having a predetermined wavelength, wherein the first and second RF shields are dimensioned so that the cavity resonates at that wavelength.

19. A test fixture for testing the RF communication operation of a plurality of RF transponders mounted on a sheet, each RF transponder having an RF antenna, comprising:

a first test fixture section including a first RF shield;

a second test fixture section including a plurality of RF shields each of which is in the shape of a cup having a mouth;

an alignment mechanism for positioning the first and second test fixture sections to abut opposite sides of the sheet so that each RF shield in the second test fixture section encircles a corresponding one of the transponder antennas so as to form, in combination with the first RF shield, a closed cavity that completely surrounds and encloses said corresponding transponder RF antenna except where the sheet separates the first RF shield from the mouth of said RF shield in the second test fixture section, wherein the distance by which the sheet separates the first RF shield from each RF shield of the second test fixture section is small enough to prevent any RF signals within each cavity from radiating outside that cavity; and

a test fixture RF antenna mounted within each cavity.

20. A test fixture according to claim 19, wherein:

the first RF shield is in the shape of a plurality of cups so that each cup has a mouth abutting the sheet; and

the alignment mechanism aligns each mouth of the second shield with a corresponding mouth of the first shield.

21. A system for performing radio frequency communications, the system comprising:

one or more first antennas;

an interrogator communicatively coupled to the one or more antennas to transmit a first command; and

a radio frequency identification (RFID) tag comprising;

one or more second antennas, at least one of the one or more second antennas being a dipole antenna;

a battery;

a random number generator to generate one or more random numbers; and

processing circuitry electrically coupled to the one or more antennas, the battery, and the random number generator, the processing circuitry configured to operate in a first state and a second state that uses more battery power than the first state, and a second state that uses more battery power than the first state, the processing circuitry further configured to transition from the first state to the second state upon receipt of the first command and to communicate a message to the interrogator at a time based at least in part on a first random number generated by the random number generator.

22. The system of claim 21, wherein the message comprises at least one random number generated by the RFID tag.

23. The system of claim 22, wherein the interrogator is further configured to transmit at least an additional command including the at least one random number to identify the RFID tag.

24. The system of claim 21, wherein the interrogator is further configured to transmit at least a second command that includes a selection indicator, and the processing circuitry is further configured to communicate the message if the selection indicator corresponds to one or more bits stored on the RFID tag.