Dual bit encoding / decoding of RFID signal

• US 20070126582A1
• Filed: 12/01/2005
• Published: 06/07/2007
• Est. Priority Date: 12/01/2005
• Status: Active Grant

• Current Assignee: Sony Corporation Of America (Sony Group Corp.)
• Original Assignee: Intel Corporation
• Inventors: Posamentier, Joshua
• Granted Patent: US 7,791,478 B2
• Time in Patent Office: Days
• US Class Current: 340/572.200
• CPC Class Codes: H04L 27/28 with simultaneous transmission of different frequencies each representing one code element

Abstract

In some embodiments of a radio frequency identification (RFID) system, multiple bits of data may be encoded at the same time based on a frequency shift key (FSK) modulation technique using multiple frequencies, by permitting any or all of the frequencies to be modulated on a carrier wave at the same time. In some embodiments a parallel but asymmetric down-conversion of the frequencies may allow both frequencies to be detected with identical filters.

Claims

1. An apparatus, comprising

a radio frequency identification (RFID) device capable of processing a radio frequency (RF) signal modulated with a first frequency and a second frequency, the two frequencies representing two-bit combinations by being simultaneously present or absent in any of these four combinations:

a) the first frequency present and the second frequency absent;

b) the first frequency absent and the second frequency present;

c) the first and second frequencies both present; and

d) the first and second frequencies both absent.

2. The apparatus of claim 1, wherein the RFID device is capable of modulating the RF signal for transmission through an antenna.

3. The apparatus of claim 1, wherein the RFID device is capable of demodulating the RF signal after the RF signal has been received through an antenna.

4. The apparatus of claim 1, wherein the RFID device comprises an RFID tag.

5. The apparatus of claim 1, wherein the RFID device comprises an RFID reader.

6. The apparatus of claim 1, wherein the RFID device comprises:

a down converter to convert the RF signal to an intermediate frequency (IF) signal that may be modulated with the first and second frequencies;

a first filter coupled to the down converter and a first detector coupled to the first filter, the first filter and the first detector to detect if the IF signal is modulated with the first frequency; and

a second filter coupled to the down converter and a second detector coupled to the second filter, the second filter and the second detector to detect if the IF signal is modulated with the second frequency.

7. The apparatus of claim 6, further comprising a circuit to convert outputs of the first and second detectors to a two-bit binary value.

8. The apparatus of claim 1, comprising:

a first down converter to convert the RF signal to an intermediate frequency (IF) signal that may be modulated with the first and second frequencies;

a second down converter coupled to the first down converter to convert the IF signal to first base band signal in which the first frequency is represented by a particular frequency at a first output;

a third down converter coupled to the first down converter to convert the IF signal to second base band signal in which the second frequency is represented by the particular frequency at a second output;

a first filter coupled to the second down converter and a first detector coupled to the first filter, the first filter and the first detector to detect a presence of the particular frequency at the first output;

a second filter coupled to the third down converter and a second detector coupled to the second filter, the second filter and the second detector to detect a presence of the particular frequency at the second output.

9. The apparatus of claim 8, further comprising a circuit coupled to the first output and the second output to convert the presence of the particular frequency at the first output and the presence of the particular frequency at the second output to a two-bit binary value.

10. The apparatus of claim 8, wherein the first filter is a low pass filter.

11. The apparatus of claim 8, wherein the second filter is a low pass filter.

12. A system, comprising:

a dipole antenna; and

a radio frequency identification (RFID) receiver circuit coupled to the dipole antenna, the RFID receiver circuit having circuitry to

demodulate a radio frequency (RF) signal modulated with two different frequencies;

simultaneously detect a presence of each of the two different frequencies modulated on the RF signal; and

map said presence into a two-bit binary value.

13. The system of claim 12, wherein the circuitry to simultaneously detect comprises circuitry to detect each of these combinations:

a presence of a first of the two frequencies, simultaneous with an absence of a second of the two frequencies;

an absence of the first frequency, simultaneous with a presence of the second frequency;

a simultaneous presence of both the first and second frequencies; and

a simultaneous absence of both the first and second frequencies.

14. The system of claim 13, wherein the circuitry to simultaneously detect comprises a down converter, a first filter, and a second filter.

15. A system comprising:

a dipole antenna;

a radio frequency identification (RFID) transmission circuit coupled to the dipole antenna, the RFID transmission circuit comprising

circuitry to convert a two-bit binary value into two different frequencies;

circuitry to modulate the first and second frequencies onto a radio frequency (RF) carrier wave;

wherein the circuitry to modulate is capable of modulating the first and second frequencies onto the carrier wave in each of these combinations;

the first frequency simultaneous with the second frequency, to represent a first two-bit binary value;

the first frequency but not the second frequency, to represent a second two-bit binary value;

the second frequency but not the first frequency, to represent a third two-bit binary value; and

neither the first frequency nor the second frequency, to represent a fourth two-bit binary value.

16. The system of claim 15, wherein the transmission circuit is part of an RFID tag.

17. The system of claim 16, wherein the two-bit binary value is part of an identification code for the RFID tag.

18. A method, comprising:

demodulating, in a radio frequency identification (RFID) device, a carrier wave modulated with first and second frequencies;

detecting a presence of the first frequency and a presence of the second frequency simultaneously in any of the combinations of

the first frequency but not the second frequency;

the second frequency but not the first frequency;

both the first and second frequencies; and

neither the first nor the second frequency; and

converting the detected combination into a two-bit binary value, wherein each of the four combinations represents a different two-bit binary value.

19. The method of claim 18, further comprising repeating said demodulating, detecting, and converting to detect an identification code for an RFID tag.

20. The method of claim 18, wherein said demodulating comprises down converting the carrier wave to an intermediate frequency modulated with the first and second frequencies.

21. The method of claim 20, where said demodulating further comprises down converting the intermediate frequency.