Dual-frequency RFID tag with isolated inputs

• US 9,087,281 B2
• Filed: 08/02/2011
• Issued: 07/21/2015
• Est. Priority Date: 06/12/2009
• Status: Active Grant

• Current Assignee: Impinj, Inc.
• Original Assignee: Impinj, Inc.
• Inventors: Maguire, Yael, Oliver, Ronald A., Diorio, Christopher J.
• Primary Examiner(s): Lim, Steven
• Assistant Examiner(s): Adnan, Muhammad
• Application Number:
  US13/196,877
• Publication Number:
  US 20110285511A1
• Time in Patent Office: 1,449 Days
• Field of Search: 340 101- 106
• US Class Current: 1/1
• CPC Class Codes: G06K 19/0724 the arrangement being a circuit for communicating at a plurality of frequencies, e.g. for managing time multiplexed communication over at least two antennas of different types
• CPC Class Codes: G06K 19/07767 the first and second communication means being two different antennas types, e.g. dipole and coil type, or two antennas of the same kind but operating at different frequencies
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H01Q 1/248 provided with an AC/DC converting device, e.g. rectennas
• CPC Class Codes: H01Q 21/30 Combinations of separate antenna units operating in different wavebands and connected to a common feeder system
• CPC Class Codes: H04Q 2213/095 User access; PIN code

Abstract

An Integrated Circuit (IC) for an RFID tag includes two electrically isolated antenna ports for connecting to two antennas, with each antenna port configured to operate at a different frequency range and/or with a different communications protocol. In some embodiments a rectifier coupled to one of the antenna ports is operable to extract energy from an electromagnetic field in a first frequency range, and a demodulator coupled to the other antenna port is operable to demodulate symbols according to an RFID protocol in a second frequency range. In some embodiments the frequency ranges are disjoint, intersecting, or one is a proper subset of the other. In some embodiments each port is coupled to its own rectifier and/or its own modulator and/or its own demodulator. In some embodiments an RFID tag includes the IC and two antennas, each operable in one of the two frequency ranges.

Claims

1. A Radio Frequency Identification (RFID) tag configured to communicate with an RFID reader, the tag comprising:

an Integrated Circuit (IC) including;

a first antenna terminal and a second antenna terminal, wherein the first antenna terminal is coupled to a first input to a first rectifier through a first coupling capacitor and the second antenna terminal is coupled to a second input to the first rectifier through a second coupling capacitor; and

a third antenna terminal and a fourth antenna terminal, wherein the third antenna terminal is coupled to a first input to a second rectifier through a third coupling capacitor and the fourth antenna terminal is coupled to a second input to the second rectifier through a fourth coupling capacitor;

a near-field antenna coupled to the first antenna terminal and the second antenna terminal; and

a far-field antenna coupled to the third antenna terminal and the fourth antenna terminal, wherein the first and second antenna-terminal pair and the third and fourth antenna-terminal pair are electrically isolated such that the near-field antenna and the far-field antenna operate independently from each other when electrically coupled to the IC, and do not share a common reference potential on the IC prior to respective couplings of the near-field antenna and the far-field antenna to the first and second rectifiers.

2. The RFID tag of claim 1, wherein at least one of the near-field antenna and the far-field antenna comprise at least one of:

a patch, a slot, a dipole, a loop, a coil, a spiral, and a horn.

3. The RFID tag of claim 1, wherein the near-field antenna and the far-field antenna operating independently from each other comprises the first rectifier being configured to operate in a first frequency range and the second rectifier being configured to operate in a second frequency range.

4. The RFID tag of claim 1, wherein the IC further includes a first demodulator coupled to the first and second antenna terminals and a second demodulator coupled to the third and fourth antenna terminals.

5. The RFID tag of claim 4, wherein the near-field antenna and the far-field antenna operating independently from each other comprises the first demodulator being operable to demodulate symbols according to a first protocol and the second demodulator being operable to demodulate symbols according to a second protocol.

6. The RFID tag of claim 1, wherein the IC further includes a first modulator coupled to the first and second antenna terminals and a second modulator coupled to the third and fourth antenna terminals.

7. The RFID tag of claim 6, wherein the near-field antenna and the far-field antenna operating independently from each other comprises the first modulator being operable to modulate symbols according to a first protocol and the second modulator being operable to modulate symbols according to a second protocol.

8. The RFID tag of claim 1, wherein the near-field antenna and the far-field antenna operating independently from each other comprises the IC being configured to extract energy from an electromagnetic field incident on one of the first and second antenna-terminal pair and the third and fourth antenna-terminal pair and a demodulator coupled to the other of the first and second antenna-terminal pair and the third and fourth antenna-terminal pair being configured to demodulate symbols according to an RFID protocol.

9. The IC of claim 8, wherein the IC is configured to extract energy and the demodulator is configured to demodulate symbols simultaneously.

10. The RFID tag of claim 1, wherein the near-field antenna and the far-field antenna are formed on a common substrate.

11. An Integrated Circuit (IC) for a Radio Frequency Identification (RFID) tag configured to communicate with an RFID reader, the IC comprising:

a first antenna terminal and a second antenna terminal, wherein the first antenna terminal is coupled to a first input to a first rectifier through a first coupling capacitor and the second antenna terminal is coupled to a second input to the first rectifier through a second coupling capacitor; and

a third antenna terminal and a fourth antenna terminal, wherein the third antenna terminal is coupled to a first input to a second rectifier through a third coupling capacitor and the fourth antenna terminal is coupled to a second input to the second rectifier through a fourth coupling capacitor, wherein

the first rectifier is configured to operate at a first frequency range;

the second rectifier is configured to operate at a second frequency range; and

the first and second antenna-terminal pair and the third and fourth antenna-terminal pair are electrically isolated such that a first antenna coupled to the first and second antenna terminals and a second antenna coupled to the third and fourth antenna terminals operate independently from each other when electrically coupled to the IC, and the first rectifier and the second rectifier do not share a common reference potential on the IC prior to respective couplings of the first and second antenna-terminal pair and the third and fourth antenna-terminal pair to the first and second rectifiers.

12. The IC of claim 11, wherein the first frequency range is one of:

disjoint with the second frequency range;

intersecting with the second frequency range, wherein the first frequency range extends into the second frequency range; and

a proper subset of the second frequency range, wherein the first frequency range is a narrower subset of the second frequency range.

13. The IC of claim 11, further comprising a demodulator coupled to the first and second antenna terminals.

14. The IC of claim 13, wherein the first antenna and the second antenna operating independently from each other comprises the demodulator being configured to demodulate symbols received in the first frequency range according to an RFID protocol and the second rectifier being configured to extract energy from an electromagnetic field in the second frequency range.

15. The IC of claim 11, further comprising a first modulator coupled to the first and second antenna terminals and a second modulator coupled to the third and fourth antenna terminals.

16. The IC of claim 15, wherein the first antenna and the second antenna operating independently from each other comprises the first modulator being configured to modulate symbols according to a first protocol and the second modulator being configured to modulate symbols according to a second protocol.

17. An Integrated Circuit (IC) for a Radio Frequency Identification (RFID) tag configured to communicate with an RFID reader, the IC comprising:

a first antenna terminal and a second antenna terminal, wherein the first antenna terminal is coupled to a first input to a first demodulator through a first coupling capacitor and the second antenna terminal is coupled to a second input to the first demodulator through a second coupling capacitor; and

a third antenna terminal and a fourth antenna terminal, wherein the third antenna terminal is coupled to a first input to a second demodulator through a third coupling capacitor and the fourth antenna terminal is coupled to a second input to the second demodulator through a fourth coupling capacitor, wherein

the first demodulator is configured to demodulate symbols according to a first protocol;

the second demodulator is configured to demodulate symbols according to a second protocol different from the first protocol; and

the first and second antenna-terminal pair and the third and fourth antenna-terminal pair are electrically isolated such that a first antenna coupled to the first and second antenna terminals and a second antenna coupled to the third and fourth antenna terminals operate independently from each other when electrically coupled to the IC, and the first demodulator and the second demodulator do not share a common reference potential on the IC prior to respective couplings of the first and second antenna-terminal pair and the third and fourth antenna-terminal pair to the first and second demodulators.

18. The IC of claim 17, further comprising a first rectifier coupled to the first and second antenna terminals and a second rectifier coupled to the third and fourth antenna terminals, wherein the first rectifier and the second rectifier are configured to operate at substantially different first and second frequency ranges.

19. The IC of claim 18, wherein the first frequency range is one of:

disjoint with the second frequency range;

intersecting with the second frequency range, wherein the first frequency range extends into the second frequency range; and

a proper subset of the second frequency range, wherein the first frequency range is a narrower subset of the second frequency range.