Systems and methods to selectively connect antennas to receive and backscatter radio frequency signals

• US 8,115,637 B2
• Filed: 06/03/2008
• Issued: 02/14/2012
• Est. Priority Date: 06/03/2008
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Tuttle, John R.
• Primary Examiner(s): TRIEU, VAN THANH
• Application Number:
  US12/132,594
• Publication Number:
  US 20110279232A1
• Time in Patent Office: 1,351 Days
• Field of Search: 340/572.1, 340/572.4, 340/572.5, 340/572.7, 340/539.1, 340/10.1, 340/10.3, 340/10.4, 343/725, 343/895, 473/351, 473/353, 455/41.1, 455/193.1, 455/271
• US Class Current: 340/572.7
• 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 19/0725 the arrangement being a circuit for emulating a plurality of record carriers, e.g. a single RFID tag capable of representing itself to a reader as a cloud of RFID tags
• CPC Class Codes: G06K 19/07773 Antenna details antennas for wireless devices, e.g. RFID tags, in general H01Q1/22
• CPC Class Codes: G06K 7/10316 using at least one antenna particularly designed for interrogating the wireless record carriers antennas in general H01Q1/22

Abstract

Systems and methods to selectively attach and control antennas via diodes and current sources. In one embodiment, a system includes: an RFID reader having a plurality of reader antennas of different polarizations to transmit radio frequency signals; and at least one RFID tag. The RFID tag includes: a plurality of tag antennas of different polarizations; a plurality of diodes coupled to the plurality of tag antennas respectively; a receiver coupled to the plurality of diodes to receive the radio frequency signals from the tag antennas when the diodes are forward biased; and a set of one or more current controllers coupled to the plurality of diodes. In a receiving mode the controllers selectively forward bias the diodes to receive the signals from the RFID reader. In a transmitting mode the controllers selectively change the state of the tag antennas to transmit data via backscattering the radio frequency signals.

Claims

1. A radio frequency identification (RFID) system, comprising:

an RFID reader having a plurality of reader antennas of different polarizations to transmit radio frequency signals; and

at least one RFID tag, the RFID tag comprising

a plurality of tag antennas of different polarizations,

a plurality of diodes coupled to the plurality of tag antennas respectively,

a receiver coupled to the plurality of diodes to receive the radio frequency signals from the tag antennas when the diodes are forward biased, and

a set of one or more current controllers coupled to the plurality of diodes, in a receiving mode the set of current controllers to forward bias at least one of the diodes to receive signals from the RFID reader, in a transmitting mode the set of current controllers to change a backscatter state of at least one of the tag antennas to transmit data via backscattering the radio frequency signals.

2. The system of claim 1, wherein the set of current controllers comprises a plurality of transistors coupled between the plurality of diodes and ground;

when in the transmitting mode a gate of the transistors is controlled according to data being transmitted to modulate the radio frequency signals backscattered by at least one of the antennas;

when in the receiving mode, the gate is applied a voltage to forward bias at least one of the diodes.

3. The system of claim 1, wherein the RFID tag further includes a controller to sequentially connect the tag antennas to a control voltage.

4. The system of claim 1, wherein the set of current controllers comprises a transistor coupled between the plurality of diodes and ground;

when in the transmitting mode a gate of the transistor is controlled according to data being transmitted to modulate backscattering by the antennas in parallel;

when in the receiving mode, the gate is applied a voltage to forward bias the diodes in parallel.

5. The system of claim 1, wherein the plurality of diodes are mounted in vicinity of respective feed points to which the diodes are connected.

6. The system of claim 1, wherein the receiver, the diodes, and the set of controllers are integrated on a single semiconductor substrate.

7. A radio frequency identification (RFID) tag, comprising:

a receiver;

a plurality of antennas;

a plurality of diodes coupled between the plurality of antennas and the receiver, the diodes to provide signal paths between the antennas and the receiver when the diodes are forward biased; and

a plurality of current controllers coupled to the plurality of diodes respectively, the current controllers controllable to selectively forward bias the diodes and to selectively ground the antennas to modulate backscatter by the antennas.

8. The RFID tag of claim 7, wherein the plurality of current controllers comprise a plurality of transistors;

wherein gates of the transistors are controllable to selectively forward bias the diodes and to selectively ground the antennas to modulate backscatter by the antennas.

9. The RFID tag of claim 7, wherein the plurality of antennas have different polarization.

10. The RFID tag of claim 9, wherein the plurality of antennas comprise:

a conductive patch having a plurality of feed points;

a ground element; and

a dielectric layer coupled between the conductive path and the ground element;

wherein the diodes are coupled to the feed points.

11. The RFID tag of claim 10, wherein the diodes are placed in vicinity of the feed points to which the diodes are connected.

12. A radio frequency identification (RFID) tag, comprising:

a receiver;

a plurality of antennas;

a plurality of diodes coupled between the plurality of antennas and the receiver; and

a transistor coupled to the plurality of diodes, when in a receiving mode the transistor to provide a current to forward bias the diodes, when forward biased the diodes to provide signals from the antennas to the receiver, when in a transmitting mode the transistor to selectively ground the antennas to modulate backscatter by the antennas.

13. The RFID tag of claim 12, wherein the plurality of antennas are formed on a planar surface to create a spherical electromagnetic antenna pattern.

14. The RFID tag of claim 12, wherein the plurality of antennas includes two dipole antennas orthogonally formed on the planar surface and a loop antenna formed on the planar surface.

15. A radio frequency device, comprising:

an antenna;

a receiver;

a diode coupled between the antenna and the receiver, when forward biased the diode to provide radio frequency signals received at the antenna to the receiver; and

a controllable circuit path coupled to the diode, the circuit path to selectively provide a forward bias current to the diode, the circuit path to change a state of the antenna to transmit data via modulating backscatter by the antenna.

16. The device of claim 15, wherein the circuit path comprises a current controller to selectively provide the forward bias current and to change the state of the antenna.

17. The device of claim 16, wherein the current controller comprises a transistor coupled between the diode and ground;

when the transistor is biased at a first voltage, the transistor provides the forward bias current to the diode;

when the transistor is biased at a second voltage, the transistor stops the forward bias current;

wherein the transistor is adjustable to change an impedance between the antenna and the ground to change the state of the antenna for backscattering when the transistor is biased according to data being transmitted.

18. The device of claim 17, wherein to change the state of the antenna to modulate backscattering, the transistor alternates between connecting the antenna to the ground and disconnecting the antenna from the ground.

19. The device of claim 15, further comprising:

an antenna system including the antenna, the antenna system having a plurality of feed points for the receiver;

wherein the diode is coupled to one of the plurality of feed points to the receiver.

20. A method implemented in a radio frequency identification system, the method comprising:

applying a first voltage to a control point of an electronic current path to forward bias a diode coupled between an antenna and a receiver, wherein when forward biased an impedance of the diode for signals propagating from the antenna to the receiver is reduced; and

applying a voltage to the control point according to data to be transmitted via the antenna to change an impedance of the current path to modulate backscattering of electromagnetic waves backscattered by the antenna.

21. The method of claim 20, wherein the electronic current path comprises a path between a source and a drain of a transistor;

and the control point comprises a gate of the transistor.