INTERMODULATION MITIGATION TECHNIQUE IN AN RFID SYSTEM

• US 20170213056A1
• Filed: 12/20/2016
• Published: 07/27/2017
• Est. Priority Date: 05/26/2005
• Status: Active Application

• Current Assignee: Transcore LP (Roper Technologies, Inc.)
• Original Assignee: Robert W Tiernay
• Inventors: TIERNAY, Robert W.
• Application Number:
  US15/384,453
• Publication Number:
  US 20170213056A1
• Time in Patent Office: Days
• CPC Class Codes: G01S 13/751 wherein the responder or reflector radiates a coded signal
• CPC Class Codes: G01S 7/36 Means for anti-jamming , e.g. ECCM, i.e. electronic counter-counter measures
• CPC Class Codes: G06K 7/10009 sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
• 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
• CPC Class Codes: G06K 7/10069 the collision being resolved in the frequency domain, e.g. by hopping from one frequency to the other frequency hopping or spread spectrum techniques H04B7/00
• CPC Class Codes: G06K 7/10475 arrangements to facilitate interaction with further interrogation devices, e.g. such that at least two interrogation devices may function and cooperate in a network of such devices
• CPC Class Codes: G07B 15/063 using wireless information transmission between the vehicle and a fixed station identification of vehicles G08G
• CPC Class Codes: H04B 1/10 Means associated with receiver for limiting or suppressing noise or interference
• CPC Class Codes: Y10T 29/49002 Electrical device making

Abstract

When multiple readers for RF transponders have to be placed in close proximity, such as in adjacent lanes of a highway toll barrier, they can be set to operate at different frequencies. When signals from two adjacent ones of the readers interfere, the resulting signal includes interference terms whose frequencies equal the sum of the reader frequencies and the difference between the reader frequencies. To remove such interference terms while passing the desired terms, a tag includes a low-pass or other frequency-selective filter.

Claims

1-16. -16. (canceled)

17. A system comprising:

a first reader to transmit a first interrogation signal to a transponder at a first frequency and to receive a response signal from the transponder at the first frequency;

a second reader to transmit a second interrogation signal to the transponder at a second frequency,

wherein said first and second interrogation signals create intermodulation products that cause interference at the transponder;

the transponder comprising;

an antenna;

a detector in electrical communication with the antenna; and

a frequency-selective filter in electrical communication with the detector to mitigate the interference.

18. The system of claim 17, wherein the detector comprises a detector diode.

19. The system of claim 17, wherein the frequency selective filter comprises an RC filter.

20. The system of claim 17, wherein the frequency selective filter comprises a low pass filter.

21. The system of claim 17, wherein the frequency selective filter comprises a band pass filter.

22. The system of claim 17, wherein the frequency selective filter comprises a high pass filter.

23. The system of claim 18, wherein the frequency selective filter comprises a low pass filter.

24. The system of claim 18, wherein the frequency selective filter comprises a band pass filter.

25. The system of claim 18, wherein the frequency selective filter comprises a high pass filter.

26. A system comprising:

a first reader to transmit a first interrogation signal to a transponder at a first frequency and receive a response signal from the transponder at a third frequency;

a second reader to transmit a second interrogation signal to the transponder at a second frequency and,

wherein said first interrogation signal or response signal and the second interrogation signal create intermodulation products that cause interference at the transponder;

the transponder comprising;

an antenna;

a detector in electrical communication with the antenna;

a frequency-selective filter in electrical communication with the detector; and

a signal processing circuit in electrical communication with the frequency-selective filter to mitigate the interference.

27. The system of claim 26, wherein the detector comprises a detector diode.

28. The system of claim 26, wherein the frequency selective filter comprises and RC filter.

29. The system of claim 26, wherein the frequency selective filter comprises a low pass filter.

30. The system of claim 26, wherein the frequency selective filter comprises a band pass filter.

31. The system of claim 26, wherein the frequency selective filter comprises a high pass filter.

32. The system of claim 27, wherein the frequency selective filter comprises a low pass filter.

33. The system of claim 27, wherein the frequency selective filter comprises a band pass filter.

34. The system of claim 27, wherein the frequency selective filter comprises a high pass filter.

35-1. The system of claim 35, wherein the detector comprises a detector diode.

43. A transponder comprising:

an antenna;

a detector in electrical communication with the antenna;

a frequency-selective filter in electrical communication with the detector to mitigate intermodulation products created by a reader supplying a first interrogation signal to a transponder at a first frequency and an interference source signal received at the transponder at a second frequency.

44. The transponder of claim 43, wherein the detector comprises a detector diode.

45. The transponder of claim 43, wherein the frequency selective filter comprises and RC filter.

46. The transponder of claim 43, wherein the frequency selective filter comprises a low pass filter.

47. The transponder of claim 43, wherein the frequency selective filter comprises a band pass filter.

48. The transponder of claim 43, wherein the frequency selective filter comprises a high pass filter.

49. The transponder of claim 44, wherein the frequency selective filter comprises a low pass filter.

50. The transponder of claim 44, wherein the frequency selective filter comprises a band pass filter.

51. The transponder of claim 44, wherein the frequency selective filter comprises a high pass filter.