Granted Patent B2

US 8,405,509 · App. 13/301,565 · Granted Mar 26, 2013

Abstract

Claims (45)

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

a plurality of antennas of different polarizations;

a plurality of diodes coupled to the plurality of antennas respectively;

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

a set of one or more current controllers coupled to the plurality of diodes;

wherein, in a receiving mode, the set of one or more current controllers is configured to forward bias at least one of the diodes to receive radio frequency signals from an RFID reader; and

wherein, in a transmitting mode, the set of one or more current controllers is configured to change a backscatter state of at least one of the antennas according to data to be transmitted from the RFID tag.

2. The RFID tag of claim 1 , wherein the set of one or more 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 RFID tag of claim 1 , further comprising:

a controller configured to sequentially connect the antennas to a control voltage.

4. The RFID tag of claim 1 , wherein the set of one or more 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 RFID tag of claim 1 , wherein the plurality of diodes are mounted in vicinity of respective feed points to which the diodes are connected.

6. The RFID tag of claim 1 , wherein the receiver 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; and

a plurality of current controllers coupled to the plurality of diodes respectively;

wherein the current controllers are configured to selectively forward bias one or more of the diodes to allow signals received via respective one or more of the antennas to reach the receiver; and

wherein the current controllers are further configured to selectively ground one or more of the antennas to modulate backscatter.

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 polarizations.

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 mounted in vicinity of the feed points to which the diodes are connected.

12. A radio frequency device, comprising:

an antenna;

a receiver;

a diode coupled between the antenna and the receiver; and

a controllable circuit path coupled to the diode, wherein the circuit path is controlled in a first mode to provide a forward bias current to the diode and in a second mode to reverse bias the diode;

wherein the forward bias current is configured to allow radio frequency signals received by the antenna to reach the receiver via the diode; and

wherein when reverse biased, the diode is configured to prevent signals received by the antenna from reaching the receiver.

13. The device of claim 12 , wherein the circuit path is configured to change a state of the antenna according to data to be transmitted via modulating backscatter by the antenna.

14. The device of claim 13 , wherein the circuit path comprises a current controller configured to selectively provide the forward bias current and change the state of the antenna.

15. The device of claim 14 , wherein the state of the antenna is changed via the circuit path connecting the antenna to ground and disconnecting the antenna from the ground.

16. The device of claim 13 , wherein the circuit path comprises a transistor coupled between the diode and ground; the transistor has a gate; when the gate is biased at a first voltage, the transistor provides the forward bias current to the diode; when the gate is biased at a second voltage, the transistor stops the forward bias current.

17. The device of claim 16 , wherein the gate is configured to be biased according to the data to be transmitted to change the state of the antenna for backscattering via changing an impedance between the antenna and the ground.

18. The device of claim 16 , wherein the transistor is configured to alternate, according to the data to be transmitted, between connecting the antenna to the ground and disconnecting the antenna from the ground.

19. The device of claim 13 , wherein the antenna has a plurality of feed points for the receiver; and the diode is coupled to one of the plurality of feed points for the receiver.

20. The device of claim 19 , further comprising:

a second diode coupled between the receiver and a second feed point of the plurality of feed points; and

a second controller circuit path coupled to the second diode to selectively forward bias and reverse bias the second diode.

Assignments (8)