System and method for communicating with an RFID transponder with reduced noise and interference

• US 6,639,509 B1
• Filed: 09/07/1999
• Issued: 10/28/2003
• Est. Priority Date: 03/16/1998
• Status: Expired due to Term

• Current Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Original Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Inventors: Martinez, Rene D.
• Primary Examiner(s): POPE, DARYL C
• Application Number:
  US09/390,461
• Time in Patent Office: 1,512 Days
• Field of Search: 340/10.4, 340/10.1, 340/572.1, 340/572.5, 340/572.4, 340/10.34, 340/10.54, 342/42, 455/127, 455/106, 455/70
• 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

Abstract

The RFID interrogator further comprises a microcontroller module adapted to provide high level commands to the interrogator, a DSP module for processing received/transmitted data and controlling radio operations, and a radio module for transmitting and receiving RF signals to/from an RFID transponder. A first embodiment of the RFID interrogator comprises an RF carrier source providing a carrier signal, a processor providing an information signal, and plural modulation stages coupled to the RF carrier source for modulating the information signal onto the carrier signal using on/off keying modulation. The plural modulation stages are controlled in unison by control signals the said processor. The plural modulation stages provide dynamic range of greater than 25 dB between respective on and off states of the modulated signal. A second embodiment of the RFID interrogator comprises an RF carrier source providing a carrier signal, a modulator receiving the carrier source and modulating an information signal thereon to provide a modulated RF signal, and an amplification stage coupled to the modulator. The amplification stage splits the modulated RF signal into first and second components, and amplifies the first and second components separately. The first and second components are thereafter recombined. The split operation of the amplification stage provides a better match with the downstream transmission path than an individual amplifier. A third embodiment of the RFID interrogator comprises an RF carrier source providing a carrier signal, a demodulator combining a received signal with the RF carrier to provide a baseband signal, and an attenuator coupled to the demodulator for absorbing high frequency components of the baseband signal. The baseband signal further comprises in phase (I) and quadrature phase (Q) components. The high frequency components of the baseband signal pass through the high-pass filter to the resistor termination, where they are absorbed.

Claims

1. A communication device, comprising:

an RF carrier source providing a carrier signal;

a processor providing an information signal; and

plural modulation stages coupled to said RF carrier source and adapted to modulate said information signal onto said carrier signal using on/off keying modulation, said plural modulation stages being controlled in unison by control signals from said processor to provide a modulated signal.

2. The communication device of claim 1, wherein at least one of said plural modulation stages comprises a mixer adapted to combine said carrier signal with said information signal to provide said modulated signal having on and off states in correspondence with said information signal.

3. The communication device of claim 1, wherein at least one of said plural modulation stages comprises an amplifier being responsive to said control signals to amplify said carrier signal only during on states of said information signal.

4. The communication device of claim 1, wherein at least one of said plural modulation stages comprises a switch having a first position coupled to a transmission path and a second position not coupled to said transmission path, said switch being responsive to said control signals to couple said modulated signal to said transmission path only during on states of said information signal.

5. The communication device of claim 4, further comprising a resistor termination coupled to said second position of said switch, said modulated signal being coupled to said resistor termination during off states of said information signal.

6. The communication device of claim 1, wherein at least one of said plural modulation stages comprises a phase shift device coupled in parallel with an amplifier, said phase shift device being responsive to said control signals to reverse phase of said modulated signal during off states of said information signal, and further comprises a combiner coupled to said amplifier and said phase shift device for combining signals therefrom, said combiner effectively canceling said modulated signal during said off states of said information signal by combining said phase reversed modulated signal thereto.

7. The communication device of claim 1, wherein said modulated signal comprises dynamic range of greater than 25 dB between respective on and off states thereof.

8. A method for communicating a signal with on/off key modulation, comprising the steps of:

providing a carrier signal; and

modulating said carrier signal with an information signal to provide a modulated signal having on and off states in correspondence with said information signal, said modulating step being carried out by plural successive stages in unison.

9. The method of claim 8, wherein the modulating step further comprises the step of coupling said modulated signal to a transmission path only during said on states of said modulated signal.

10. The method of claim 8, wherein the modulating step further comprises the step of amplifying said modulated signal only during said on states of said modulated signal.

11. The method of claim 8, wherein the modulating step further comprises the step of mixing said carrier signal with said information signal.

12. A communication device, comprising:

an RF carrier source providing a carrier signal;

a modulator receiving said carrier source and modulating an information signal thereon to provide a modulated RF signal;

an amplification stage coupled to said modulator, said amplification stage splitting said modulated RF signal into first and second components and amplifying said first and second components separately, said first and second components being thereafter recombined to provide an amplified modulated RF signal; and

a receiving stage adapted to receive a backscattered modulated signal from an radio frequency identification (RFID) transponder, wherein said amplification stage is matched to said receiving stage to thereby reduce leakage of said amplified modulated RF signal into said received backscatter modulated signal.

13. The communication device of claim 12, further comprising a circulator adapted to pass said amplified modulated signal in a first direction therethrough for transmission to an RFID transponder and said received backscatter modulated signal from said RFID transponder in a second direction therethrough opposite said first direction.

14. The communication device of claim 12, wherein said amplification stage further comprises a first quadrature hybrid adapted to split said modulated RF signal into said first and second components having a phase difference therebetween.

15. The communication device of claim 12, wherein said amplification stage further comprises first and second power amplifiers receiving said first and second components respectively and providing amplification thereto.

16. The communication device of claim 14, wherein said amplification stage further comprises a second quadrature hybrid adapted to combine said first and second components of said modulated RF signal amplified by said first and second power amplifiers, respectively.

17. The communication device of claim 12, wherein said phase difference further comprises approximately 90°

.

18. The communication device of claim 16, wherein said first and second quadrature hybrids further comprise respective isolated signal paths for communicating reflected power from said first and second power amplifiers therefrom.

19. The communication device of claim 18, wherein said amplification stage further comprises resistor terminations coupled to said isolated signal paths.

20. The communication device of claim 15, wherein said first and second power amplifiers are each driven at a saturation level.

21. A communication device, comprising:

an RF carrier source providing a carrier signal;

a modulator receiving said carrier source and modulating an information signal thereon using on/off keying to provide a modulated RF signal; and

an amplification stage coupled to said modulator, said amplification stage being driven at a saturation level to provide an amplified modulated RF signal.

22. The communication device of claim 21, wherein said amplification stage splits said modulated RF signal into first and second components and amplifies said first and second components separately, said first and second components being recombined thereafter.

23. The communication device of claim 22, wherein said amplification stage further comprises a first quadrature hybrid adapted to split said modulated RF signal into said first and second components having a phase difference therebetween.

24. The communication device of claim 23, wherein said amplification stage further comprises first and second power amplifiers receiving said first and second components respectively and providing amplification thereto.

25. The communication device of claim 24, wherein said amplification stage further comprises a second quadrature hybrid adapted to combine said first and second components of said modulated RF signal amplified by said first and second power amplifiers, respectively.

26. The communication device of claim 23, wherein said phase difference further comprises approximately 90°

.

27. The communication device of claim 24, wherein said first and second quadrature hybrid further comprises respective isolated signal paths for communicating reflected power from said first and second power amplifiers therefrom.

28. The communication device of claim 27, wherein said amplification stage further comprises resistor terminations coupled to said isolated signal paths.

29. A method for communicating a signal, comprising the steps of:

providing a carrier signal;

modulating an information signal onto said carrier signal using on/off keying to provide a modulated RF signal; and

amplifying said modulated RF signal at a saturation level to reduce amplitude variation of said modulated signal.

30. The method of claim 29, wherein said amplifying step further comprises splitting said modulated RF signal into first and second components and amplifying said first and second components separately.

31. The method of claim 30, further comprising the step of recombining said first and second components after said amplifying step.

32. The method of claim 30, wherein said amplifying step further comprises splitting said modulated RF signal into said first and second components having a phase difference therebetween.

33. The method of claim 32, wherein said phase difference comprises 90°

.

34. The method of claim 30, further comprising the step of communicating reflected power produced in said amplifying step to a resistor termination.

35. A device for communicating signals to and from a radio frequency identification (RFID) transponder, comprising:

an RF carrier source providing a carrier signal;

a transmitter adapted to transmit said carrier signal to said RFID transponder at a desired power level;

a demodulator mixing a backscatter modulated signal received from said RFID transponder with said RF carrier to provide a baseband signal; and

an attenuator coupled to said demodulator for absorbing high frequency components of said baseband signal.

36. The communication device of claim 35, wherein said baseband signal further comprises in phase (I) and quadrature phase (Q) components.

37. The communication device of claim 36, wherein said attenuator further comprises a high-pass filter and a resistor termination, said high frequency components of said baseband signal passing through said high-pass filter to said resistor termination.

38. The communication device of claim 37, further comprising a circulator adapted to pass said carrier signal in a first direction therethrough for transmission to said RFID transponder and said backscatter modulated signal in a second direction therethrough opposite said first direction, said circulator being coupled to said demodulator.

39. The communication device of claim 38, further comprising a directional coupler disposed closely adjacent to a final amplification stage of said transmitter, said directional coupler passing said carrier signal to said demodulator.

40. A method for communicating signals to and from a radio frequency identification (RFID) transponder, comprising the steps of:

providing a carrier signal;

transmitting said carrier signal to said RFID transponder at a desired power level;

mixing a backscatter modulated signal received from said RFID transponder with said carrier signal to provide a baseband signal; and

absorbing high frequency components of said baseband signal.

41. The method of claim 40, wherein said baseband signal further comprises in phase (I) and quadrature phase (Q) components.

42. The method of claim 40, further comprising the step of passing said carrier signal in a first direction through a circulator and said backscatter modulated signal in a second direction through said circulator opposite said first direction.