H-field shaping using a shorting loop

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

a RFID reader, including:

a plurality of antennas that each is configured to generate an electromagnetic field that includes a magnetic field component, and

a plurality of shorting loops that each at least partially surrounds the antenna, wherein each shorting loop is configured to distort the magnetic field component to improve a definition of a border of a read region related to each antenna, wherein each read region together form a plurality of adjacent read regions; and

a plurality of RFID tokens, including a first RFID token that is within a first read region, a second RFID token that is within a second read region, and a third RFID token that is outside of and adjacent to the first read region, and outside of the second region,

wherein the RFID reader operates to detect that the first RFID token is within the first read region, to detect that the second RFID token is within the second read region, not to detect that the third RFID token is within the first read region, and not to detect that the third RFID token is within the second region, in accordance with each shorting loop improving the definition of the border of the read region related to each antenna.

2. The RFID system of claim 1 , wherein each shorting loop is displaced from each antenna by a gap, wherein a size of the gap is selected to balance a read range and a discrimination factor.

3. The RFID system of claim 2 , wherein the discrimination factor corresponds to a signal strength difference between the first RFID token and the third RFID token.

4. The RFID system of claim 2 , wherein the gap is a constant distance between the shorting loop and the antenna.

5. The RFID system of claim 2 , wherein the gap is a variable gap.

6. The RFID system of claim 1 , wherein the RFID reader is configured to provide power to a corresponding antenna, to provide a first modulated signal to the corresponding antenna, and to receive a second modulated signal from the corresponding antenna.

7. The RFID system of claim 1 , wherein each antenna is a circular antenna, wherein each shorting loop is a circular shorting loop, and wherein the circular shorting loop surrounds the circular antenna.

8. The RFID system of claim 1 , wherein each shorting loop is made of a copper material.

9. The RFID system of claim 1 , wherein each shorting loop is configured to constrain the electromagnetic field outside of each read region.

10. The RFID system of claim 1 , wherein a first signal strength of the first RFID token is more than 10 dB greater than a second signal strength of the third RFID token that is adjacent to the first RFID token.

11. The RFID system of claim 1 , wherein the plurality of RFID tokens includes a first set that has the first RFID token, a second set that has the second RFID token, and a third set that has the third RFID token;

wherein the first set is within the first read region, the second set is within the second read region, and the third set is outside of the first read region; and

wherein the RFID reader operates to detect that the first set is within the first read region, to detect that the second set is within the second read region, and not to detect that the third set is within the first read region.

12. The RFID system of claim 1 , wherein the plurality of RFID tokens includes a first stack that has the first RFID token, a second stack that has the second RFID token, and a third stack that has the third RFID token; and

wherein the first stack steers the magnetic field component vertically inside the first read region, and wherein the second stack steers the magnetic field component vertically inside the second read region.

13. The RFID system of claim 1 , wherein the plurality of RFID tokens includes a first stack that has the first RFID token, a second stack that has the second RFID token, and a third stack that has the third RFID token;

wherein the third stack is adjacent to the first stack; and

wherein the RFID reader operates to detect that the first stack is within the first read region, to detect that the second stack is within the second read region, and not to detect that the third stack is within the first read region.

14. The RFID system of claim 1 , wherein the RFID reader further includes:

a motherboard; and

a plurality of daughter boards that are coupled to the motherboard and to the plurality of antennas.

15. The RFID system of claim 1 , wherein the RFID reader further includes:

a motherboard; and

a plurality of daughter boards that are coupled to the motherboard and to the plurality of antennas, wherein one of the plurality of daughter boards is coupled to more than one of the plurality of antennas.

16. The RFID system of claim 1 , wherein the RFID reader further includes:

a motherboard; and

a plurality of daughter boards that are coupled to the motherboard and to the plurality of antennas, wherein one of the plurality of daughter boards is configured to drive more than one of the plurality of antennas using multiplexed signals.

17. The RFID system of claim 1 , wherein the RFID reader further includes:

a motherboard; and

a plurality of daughter boards that are coupled to the motherboard and to the plurality of antennas, wherein one of the plurality of daughter boards is configured to perform simultaneous reads using more than one of the plurality of antennas.

18. A method of performing radio frequency identification (RFID), comprising:

providing a RFID reader, including:

providing a plurality of antennas that each generates an electromagnetic field that includes a magnetic field component, and

providing a plurality of shorting loops that each at least partially surrounds the antenna, wherein each shorting loop distorts the magnetic field component to improve a definition of a border of a read region related to each antenna, wherein each read region together form a plurality of adjacent read regions;

providing a plurality of RFID tokens, including a first RFID token that is within a first read region, a second RFID token that is within a second read region, and a third RFID token that is outside of and adjacent to the first read region, and outside of the second read region;

detecting that the first RFID token is within the first read region, in accordance with each shorting loop improving the definition of the border of the read region related to each antenna;

detecting that the second RFID token is within the second read region, in accordance with each shorting loop improving the definition of the border of the read region related to each antenna;

not detecting that the third RFID token is within the first read region, in accordance with each shorting loop improving the definition of the border of the read region related to each antenna; and

not detecting that the third RFID token is within the second read region, in accordance with each shorting loop improving the definition of the border of the read region related to each antenna.

19. The method of claim 18 , further comprising:

driving more than one of the plurality of antennas using multiplexed signals.