Method of allocating digital data coming from transponders and a reader thereto

• US 9,013,277 B2
• Filed: 12/01/2008
• Issued: 04/21/2015
• Est. Priority Date: 12/11/2007
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Muehlmann, Ulrich
• Primary Examiner(s): Zimmerman, Brian
• Assistant Examiner(s): Lau, Kevin
• Application Number:
  US12/747,080
• Publication Number:
  US 20100265044A1
• Time in Patent Office: 2,332 Days
• Field of Search: None
• US Class Current: 340/10.4
• 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 7/10019 resolving collision on the communication channels between simultaneously or concurrently interrogated record carriers. collision between the communication channels used by wireless communication devices, where the solution is not particularly adapted for RFIDs or the like, H04W74/08

Abstract

In a method of allocating digital data (55a, 55b) coming from transponders, a reader (1) receives a first signal (13) that comprises a first signal component (7) coming from a first transponder (2) and a second signal component (8) coming from a second transponder (3). The digital data (55a) coming from the first transponder (2) are encoded in the first signal component (7) and digital data (55b) coming from the second transponder (3) are encoded in the second signal component (8). Second and third signals (10, 11) are generated by subjecting the first signal (13) to an in-phase and to an in-quadrature demodulation. The digital data (55a, 55b) of the first and second transponders (2, 3) are encoded in the second and third signals (10, 11). Clusters (51-54) of the digital data (55 a, 55b) associated with a constellation diagram, which is related to the second and third signals (10, 11), are allocated to the first and second transponder (2, 3).

Claims

1. A method of allocating digital data coming from transponders, comprising the steps of:

receiving at a reader a first signal that comprises a first signal component coming from a first transponder and a second signal component coming from a second transponder during a same time slot in which the first and second transponders respond to an inventory command from the reader at different time points, wherein digital data coming from the first transponder are encoded in the first signal component and digital data coming from the second transponder are encoded in the second signal component;

generating second and third signals by subjecting the first signal to an in-phase and to an in-quadrature demodulation; and

allocating clusters of the digital data associated with a constellation diagram, which is related to the second and third signals, to the first and second transponders, wherein a first pair of the clusters is only related to the first transponder, a second pair of the clusters is only related to the second transponder, the centers of gravity of the first pair of the clusters are symmetric to the origin of the constellation diagram, and the centers of gravity of the second pair of the clusters are symmetric to the origin of the constellation diagram.

2. The method of claim 1, wherein the digital data are encoded in the first and second signal components by means of an Amplitude Shift Keying modulation scheme.

3. The method of claim 1, further comprising

mapping the digital data of the first pair of clusters to a first pair of constellation points within the constellation diagram, and mapping the digital data of the second pair of clusters to a second pair of constellation points;

the constellation points of the first pair of constellation points being symmetric to the origin of the constellation diagram and the constellation points of the second pair of constellation points being symmetric to the origin of the constellation diagram.

4. The method of claim 3, wherein the coordinates of the constellation points of the first pair of constellation points are (1;

j) and (−

1, −

j) and the coordinates of the constellation points of the second pair of constellation points are (−

1;

j) and (1, −

j).

9. The method of claim 1, wherein the first pair of the clusters comprises a first cluster that only corresponds to logical 1 of the first signal component coming from the first transponder and a second cluster that only corresponds to logical 0 of the first signal component coming from the first transponder.

10. The method of claim 9, wherein the second pair of the clusters comprises a third cluster that only corresponds to logical 1 of the second signal component coming from the second transponder and a fourth cluster that only corresponds to logical 0 of the second signal component coming from the second transponder.

5. A reader configured to communicate with a plurality of transponders, comprising:

a receiver configured to receive a first signal that comprises a first signal component coming from a first transponder and a second signal component coming from a second transponder during a same time slot in which the first and second transponders respond to an inventory command from the reader at different time points, wherein digital data coming from the first transponder are encoded in the first signal component and digital data coming from the second transponder are encoded in the second signal component; and

an IQ-demodulator configured to generate second and third signals by subjecting the first signal to an in-phase and to an in-quadrature demodulation;

wherein the reader is configured to allocate clusters of the digital data associated with a constellation diagram, which is related to the second and third signals, to the first and second transponders, wherein a first pair of the clusters is only related to the first transponder, a second pair of the clusters is only related to the second transponder, the centers of gravity of the first pair of the clusters are symmetric to the origin of the constellation diagram, and the centers of gravity of the second pair of the clusters are symmetric to the origin of the constellation diagram.

6. The reader of claim 5, wherein the digital data are encoded in the first and second signal components by means of an Amplitude Shift Keying modulation scheme.

7. The reader of claim 5, further being configured to map the digital data of the first pair of clusters to a first pair of constellation points within the constellation diagram, and to map the digital data of the second pair of clusters to a second pair of constellation points;

the constellation points of the first pair of constellation points being symmetric to the origin of the constellation diagram; and

the constellation points of the second pair of constellation points being symmetric to the origin of the constellation diagram.

8. The reader of claim 7, wherein the coordinates of the constellation points of the first pair of constellation points are (1;

j) and (−

1, −

j) and the coordinates of the constellation points of the second pair of constellation points are (−

1;

j) and (1, −

j).

11. The reader of claim 5, wherein the first pair of the clusters comprises a first cluster that only corresponds to logical 1 of the first signal component coming from the first transponder and a second cluster that only corresponds to logical 0 of the first signal component coming from the first transponder.

12. The reader of claim 11, wherein the second pair of the clusters comprises a third cluster that only corresponds to logical 1 of the second signal component coming from the second transponder and a fourth cluster that only corresponds to logical 0 of the second signal component coming from the second transponder.