RFID Reader

• US 20100289617A1
• Filed: 12/07/2006
• Published: 11/18/2010
• Est. Priority Date: 12/16/2005
• Status: Active Grant

• Current Assignee: SureFlap Ltd.
• Original Assignee: Cambridge Resonant Technologies Ltd. (Merck & Co., Inc.)
• Inventors: Hill, Nicholas Patrick Roland
• Granted Patent: US 9,013,268 B2
• Time in Patent Office: Days
• US Class Current: 340/5.61
• CPC Class Codes: A01K 11/006 Automatic identification systems for animals, e.g. electronic devices, transponders for animals identification systems for access to feeding pens A01K1/0209; ear tags with electronic identification means A01K11/004
• CPC Class Codes: A01K 15/021 Electronic training devices specially adapted for dogs or cats
• CPC Class Codes: E05F 15/76 responsive to devices carried by persons or objects, e.g. magnets or reflectors E05F15/77 takes precedence
• CPC Class Codes: E05F 15/77 using wireless control
• CPC Class Codes: G01V 15/00 Tags attached to, or associated with, an object, in order to enable detection of the object record carriers for use with machines having a detectable tag or marker G06K19/00
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• 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 7/10366 the interrogation device being adapted for miscellaneous applications
• CPC Class Codes: G07C 9/28 the pass enabling tracking or indicating presence

Abstract

Embodiments of the invention relate to the field of RFED (radio frequency identification). Some particularly preferred embodiments relate to a high-Q, so-called “full duplex” (FDX) RFID Reader. An RFID tag reader, the reader comprising: an electromagnetic (em) field generator for generating an electromagnetic (em) field for modulation by said tag, said modulation comprising modulated load of said em field by said tag; a detector system responsive to fluctuations in strength of said em field at said reader; a negative feedback system responsive to said detector system to provide a control signal for said em field generator for controlling said em field generator to reduce said detected fluctuations; and a demodulator responsive to said control of said em field to demodulate said em field modulation by said tag.

Claims

1. An RFID tag reader, the reader comprising:

an electromagnetic (EM) field generator for generating an electromagnetic (EM) field for modulation by said tag, said modulation comprising modulated load of said EM field by said tag;

a detector system responsive to fluctuations in strength of said em field at said reader;

a negative feedback system responsive to said detector system to provide a control signal for said EM field generator for controlling said EM field generator to reduce said detected fluctuations; and

a demodulator responsive to said control of said EM field to demodulate said EM field modulation by said tag.

2. A tag reader as claimed in claim 1 configured for simultaneous operation of said EM field generator and said detector system.

3. A tag reader as claimed in claim 1 wherein said tag comprises a passive tag, and wherein said EM field generator is configured to generate a substantially continuous EM field to power said tag.

4. A tag reader as defined in claim 1 wherein at least one of said EM em field generator and said detector comprises a resonant circuit including a coil with a Q of greater than 50, more preferably greater than 100.

5. A tag reader as defined in claim 1 wherein said EM field generator and said detector system share a common coil for generating said EM field and detecting said EM field fluctuations.

6. A tag reader as defined in claim 1 wherein said feedback system includes an envelope detector to detect an envelope of said modulated EM field.

7. A tag reader as defined in claim 1 wherein said feedback system further comprises a pulse generator to drive said EM field generator responsive to said detector system.

8. A tag reader as defined in claim 7 wherein said pulse generator is configured to control a power supply to said EM field generator, and further comprising a circuit to provide a demand signal, said demand signal being responsive to an energy drawn per cycle of said EM field from said power supply by said EM field generator, and wherein said demodulator is configured to demodulate said demand signal.

9. A tag reader as defined in claim 8 further comprising a control system to control a tuning of said detector system responsive to a quality of said demodulated demand signal.

10. A tag reader as defined in claim 1 wherein said EM field generator and said detector system comprise a shared controllable electrical resonator.

13. A tag reader as defined in claim 1 wherein said modulated load of said EM field by said tag or transponder comprises modulated absorption of said EM field by said tag or transponder.

14. A tag reader as claimed in claim 1 incorporated into an animal flap.

15. A tag reader as claimed in claim 14 wherein said animal flap further comprises an entry control device to inhibit entry of an animal through said animal flap and, responsive to said tag reader detecting an animal bearing a said tag, to allow entry of said tagged animal through said animal flap.

16. An RFID tag reader claim 1, configured for retrofitting to an animal flap in combination with

an animal entry control device to inhibit entry of an animal through said animal flap and, responsive to said tag reader detecting an animal bearing a said tag, to allow entry of said tagged animal through said animal flap,

wherein said tag reader and said animal entry control device form a pet entry control system.

11. (canceled)

12. (canceled)

17. (canceled)

18. An RFID system including a transponder and a reader for the transponder, wherein the reader is configured to use negative feedback to increase the stability of the amplitude of a resonance in the reader in the presence of a modulating transponder.

19. An RFID system as claimed in claim 18 wherein a level of drive into the resonance of a resonant circuit is measured to demodulate said transponder modulation.

20. An RFID system as claimed in claim 18 wherein the residual voltage variation of said amplitude is measured to demodulate said transponder modulation.

21. An RFID system as claimed in claim 18 wherein the system is a full-duplex system.

22. An RFID system as claimed in claim 18 wherein the system is a half-duplex system.

23. An RFID system as claimed in claim 18 wherein said reader comprises a resonant circuit with at least two capacitive paths and a FET to control a variable duty cycle of these paths to match the resonance to a range of frequencies.

24. An RFID system as claimed in claim 19 configured to use the shape of said demodulated modulation to tune the reader to the transponder frequency.

25. A method of remotely interrogating a transponder, the method comprising:

generating an electromagnetic (EM) field for modulation by said transponder, said modulation comprising modulated load of said em field by said transponder;

detecting fluctuations in said EM field caused by said modulation;

applying feedback to said EM field generating to compensate said detected fluctuations; and

detecting said applied feedback to demodulate said modulation of said EM field by said transponder.

26. Apparatus for remotely interrogating a transponder, the apparatus comprising:

means for generating an electromagnetic (EM) field for modulation by said transponder, said modulation comprising load absorption of said EM field by said transponder;

means for detecting fluctuations in said EM field caused by said modulation;

means for applying feedback to said EM field generating to compensate said detected fluctuations; and

means for detecting said applied feedback to demodulate said modulation of said EM field by said transponder.