RFID reader utilizing an analog to digital converter for data acquisition and power monitoring functions

• US 20050258940A1
• Filed: 05/18/2004
• Published: 11/24/2005
• Est. Priority Date: 05/18/2004
• Status: Active Grant

• Current Assignee: Assa Abloy AB
• Original Assignee: Assa Abloy Identification Technology Group AB (Assa Abloy AB)
• Inventors: Quan, Ralph W.
• Granted Patent: US 7,180,403 B2
• Time in Patent Office: Days
• US Class Current: 340/10.300
• 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 7/086 sensing passive circuit, e.g. resonant circuit transponders
• CPC Class Codes: G06K 7/10128 the step consisting of detection of the presence of one or more record carriers in the vicinity of the interrogation device

Abstract

A reader for an RFID system includes an internal power source, a signal generator for generating a detection signal containing analog data and an excitation signal, a transmitting antenna for transmitting the detection and excitation signals, and a receiving antenna for receiving a transponder data signal from a transponder containing digital data. Receiver electronics are coupled with the receiving antenna for conditioning the transponder data signal before reading the digital data. The reader further includes a single-chip microcontroller coupled with the internal power source and the receiver electronics. The single-chip microcontroller has an analog to digital converter to measure the declining power level of the internal power source and to acquire the analog data from the detection signal and the digital data from the transponder data signal. The single-chip microcontroller also includes a firmware and/or software-based demodulator for demodulating the transponder data signal to read the digital data.

Claims

1. A reader for an RFID system comprising:

a signal generator for generating a detection signal containing analog data and for generating an excitation signal;

a transmitting antenna coupled with said signal generator for transmitting said detection signal and said excitation signal into a space surrounding said transmitting antenna;

a receiving antenna for receiving a transponder data signal at a voltage value containing digital data from a transponder in said space;

receiver electronics coupled with said receiving antenna for conditioning said transponder data signal to place said transponder data signal in a condition for reading said digital data;

an internal power source for supplying electrical operating power to said reader, said internal power source having a declining power level as a function of use; and

a single-chip microcontroller coupled with said internal power source and said receiver electronics, said single-chip microcontroller including an analog to digital converter to acquire said analog data from said detection signal and said digital data from said transponder data signal and to convert said analog data from said detection signal to converted digital data.

2. The reader of claim 1, wherein said receiver electronics includes a receiver electronics input from said receiving antenna, a receiver electronics output to said single-chip microcontroller, and a plurality of relatively low-cost simple electrical components selected from the group consisting of resistors, diodes, capacitors, and electrical switches, and excludes relatively high-cost complex multi-stage band pass amplifiers.

3. The reader of claim 1, wherein said single-chip microcontroller further includes a software and/or firmware-based demodulator for demodulating said transponder data signal to read said digital data from said transponder data signal.

4. The reader of claim 1, wherein said receiving antenna and said transmitting antenna are both included in a single dual-function antenna.

5. The reader of claim 2, wherein said receiver electronics includes a resistor divider section comprising first and second series resistors at said receiver electronics input forming a voltage divider to reduce said voltage value of said transponder data signal and third and fourth series resistors downstream of said first and second series resistors positioned between ground and said power supply and a blocking capacitor positioned in parallel with the second series resistor upstream of said third and fourth series resistors to maintain said transponder data signal at said receiver electronics output in a voltage range between about ground and said power supply, inclusive.

6. The reader of claim 2, wherein said receiver electronics includes a peak detector section comprising a rectifier at said receiver electronics input to rectify said voltage value of said transponder data signal and a pair of series resistors downstream of said rectifier positioned between ground and said power supply and a blocking capacitor positioned between said rectifier and said pair of series resistors to maintain said transponder data signal at said receiver electronics output in a voltage range between about ground and said power supply, inclusive.

7. The reader of claim 6, wherein said rectifier includes a diode and said peak detector section further comprises a detector capacitor and a detector resistor, said detector capacitor and detector resister positioned in parallel with one another and in parallel with said blocking capacitor downstream of said diode and upstream of said pair of series resistors.

8. The reader of claim 2, wherein said receiver electronics includes an integrator section comprising a rectifier and an integrator in series at said receiver electronics input and coupled with said receiver electronics output, said receiver electronics output coupled with said analog to digital converter.

9. The reader of claim 8, wherein said rectifier includes a diode and said integrator includes an integrator resistor and integrator capacitor in series with said diode, said integrator section further comprising a paired grounding switch resistor and grounding switch in series with one another and in parallel with said integrator capacitor downstream of said integrator resistor, said paired grounding switch resistor and grounding switch coupling said integrator capacitor with ground when said grounding switch is closed and coupling said integrator capacitor with said analog to digital converter when said grounding switch is open.

10. The reader of claim 8, wherein said rectifier includes a diode and said integrator includes an integrator resistor and integrator capacitor in series with said diode, said integrator section further comprising a charging switch in series with said integrator capacitor and ground, said charging switch coupling said integrator capacitor with said receiving antenna when said charging switch is closed and decoupling said integrator capacitor from said receiving antenna when said charging switch is open.

11. The reader of claim 1, wherein said reader further comprises a sample and hold circuit having one or more sample times for isolating points on said detection signal where said analog data is to be acquired and for isolating points on said transponder data signal where said digital data is to be acquired.

12. The reader of claim 11, wherein said sample and hold circuit is included in said analog to digital converter of said single-chip microcontroller.

13. The reader of claim 11, wherein said microcontroller controls said one or more sample times of said sample and hold circuit and adjusts said one or more sample times in response to different values of carrier frequency, data rate, and/or modulation type of said transponder data signal.

14. The reader of claim 11, wherein said microcontroller controls said one or more sample times of said sample and hold circuit and adjusts said one or more sample times to enable detection of a transponder from a limited sampling of detection signals.

15. The reader of claim 5, wherein said receiver electronics further includes a peak detector section comprising a rectifier at said receiver electronics input to rectify said voltage value of said transponder data signal and a pair of series resistors downstream of said rectifier positioned between ground and said power supply and a blocking capacitor positioned between said rectifier and said pair of series resistors to maintain said transponder data signal at said receiver electronics output in a voltage range between about ground and said power supply, inclusive.

16. The reader of claim 15, wherein said rectifier includes a diode and said peak detector section further comprises a detector capacitor and a detector resistor, said detector capacitor and detector resister positioned in parallel with one another and in parallel with said blocking capacitor downstream of said diode and upstream of said pair of series resistors.

17. The reader of claim 5, wherein said receiver electronics further includes an integrator section comprising a rectifier and an integrator in series at said receiver electronics input and coupled with said receiver electronics output, said receiver electronics output coupled with said analog to digital converter.

18. The reader of claim 17, wherein said rectifier includes a diode and said integrator includes an integrator resistor and integrator capacitor in series with said diode, said integrator section further comprising a paired grounding switch resistor and grounding switch in series with one another and in parallel with said integrator capacitor downstream of said integrator resistor, said paired grounding switch resistor and grounding switch coupling said integrator capacitor with ground when said grounding switch is closed and coupling said integrator capacitor with said analog to digital converter when said grounding switch is open.

19. The reader of claim 17, wherein said rectifier includes a diode and said integrator includes an integrator resistor and integrator capacitor in series with said diode, said integrator section further comprising a charging switch in series with said integrator capacitor and ground, said charging switch coupling said integrator capacitor with said receiving antenna when said charging switch is closed and decoupling said integrator capacitor from said receiving antenna when said charging switch is open.

20. The reader of claim 6, wherein said receiver electronics further includes an integrator section comprising an integrator at said receiver electronics input and coupled with said receiver electronics output, said receiver electronics output coupled with said analog to digital converter.

21. The reader of claim 15, wherein said receiver electronics further includes an integrator section comprising an integrator at said receiver electronics input and coupled with said receiver electronics output, said receiver electronics output coupled with said analog to digital converter.

22. The reader of claim 1 further comprising a transmitting tuning capacitor paired with said transmitting antenna and a receiving tuning capacitor paired with said receiving antenna.

23. The reader of claim 22, wherein said receiving tuning capacitor and said transmitting tuning capacitor are both included in a single dual-function tuning capacitor.

24. The reader of claim 22, wherein said transmitting tuning capacitor and/or said receiving tuning capacitor is a first tuning capacitor for tuning a first reader antenna to a higher carrier frequency, said reader further comprising a second tuning capacitor for tuning a second reader antenna to a lower carrier frequency,

25. A reader for an RFID system comprising:

a signal generator for generating a detection signal containing analog data and for generating an excitation signal;

a transmitting antenna coupled with said signal generator for transmitting said detection signal and said excitation signal into a space surrounding said transmitting antenna;

a receiving antenna for receiving a transponder data signal at a voltage value containing digital data from a transponder in said space;

receiver electronics coupled with said receiving antenna for conditioning said transponder data signal to place said transponder data signal in a condition for reading said digital data; and

a single-chip microcontroller coupled with said receiver electronics, said single-chip microcontroller including an analog to digital converter to acquire said analog data from said detection signal and said digital data from said transponder data signal and to convert said analog data from said detection signal to converted digital data, said single-chip microcontroller further including a demodulator for demodulating said transponder data signal to read said digital data from said transponder data signal.

26. The reader of claim 25, wherein said receiver electronics includes a receiver electronics input from said receiving antenna, a receiver electronics output to said single-chip microcontroller, and a plurality of relatively low-cost simple electrical components selected from the group consisting of resistors, diodes, capacitors, and electrical switches, and excludes one or more relatively high-cost complex multi-stage band pass amplifiers.

27. The reader of claim 25, wherein said receiving antenna and said transmitting antenna are both included in a single dual-function antenna.

28. A method for operating a reader for an RFID system comprising:

generating a detection signal containing analog data in a detection mode of operation;

transmitting said detection signal from a transmitting antenna into a space surrounding said transmitting antenna to detect a proximal transponder;

generating an excitation signal in an excitation mode of operation;

transmitting said excitation signal from said transmitting antenna into said space to power up said proximal transponder;

generating a transponder data signal at said proximal transponder in response to said excitation signal and propagating said transponder data signal through said space from said proximal transponder;

receiving said transponder data signal with a receiving antenna, wherein said transponder data signal is at a voltage value and contains digital data;

conditioning said transponder data signal with receiver electronics coupled with said receiving antenna to place said transponder data signal in a condition for reading said digital data;

coupling an analog to digital converter in a single-chip microcontroller with an internal power source supplying electrical operating power to said reader, said internal power source having a declining power level as a function of use and with said receiver electronics;

coupling said analog to digital converter with said receiver electronics;

acquiring said analog data from said detection signal with said analog to digital converter for use in said detection mode; and

acquiring said digital data from said transponder data signal with said analog to digital converter for use in a signal reading mode of operation.

29. The method of claim 28, wherein said receiver electronics includes a plurality of relatively low-cost simple electrical components selected from the group consisting of resistors, diodes, capacitors, and electrical switches, and excludes one or more relatively high-cost complex multi-stage band pass amplifiers.

30. The method of claim 28 further comprising demodulating said transponder data signal with software and/or firmware contained in said single-chip microcontroller to read said digital data from said transponder data signal in said signal reading mode.

31. The method of claim 28, wherein said receiving antenna and said transmitting antenna are both included in a single dual-function antenna.

32. The method of claim 28, wherein said transponder data signal is conditioned with said receiver electronics by reducing said voltage value of said transponder data signal and maintaining said transponder data signal in a voltage range between about ground and a power supply for said reader, inclusive.

33. The method of claim 28, wherein said transponder data signal is conditioned with said receiver electronics by rectifying said voltage value of said transponder data signal and maintaining said transponder data signal in a voltage range between about ground and a power supply for said reader, inclusive.

34. The method of claim 28, wherein said transponder data signal is conditioned with said receiver electronics by rectifying said voltage value of said transponder data signal and integrating said transponder data signal over one or more cycles of a carrier frequency of said transponder data signal.

35. The method of claim 28, further comprising isolating points on said detection signal where said analog data is to be acquired with a sample and hold circuit having one or more sample times.

36. The method of claim 28, further comprising isolating points on said transponder data signal where said digital data is to be acquired with a sample and hold circuit having one or more sample times.

37. The method of claim 35, wherein said sample and hold circuit is included in said analog to digital converter of said single-chip microcontroller.

38. The method of claim 36, wherein said sample and hold circuit is included in said analog to digital converter of said single-chip microcontroller.

39. The method of claim 35, wherein said microcontroller controls said one or more sample times of said sample and hold circuit and adjusts said one or more sample times to enable detection of said proximal transponder from a limited sampling of detection signals.

40. The method of claim 36, wherein said microcontroller controls said one or more sample times of said sample and hold circuit and adjusts said one or more sample times in response to different values of carrier frequency, data rate, and/or modulation type of said transponder data signal.

41. The method of claim 32, wherein said transponder data signal is conditioned with said receiver electronics by rectifying said voltage value of said transponder data signal and maintaining said transponder data signal in a voltage range between about ground and a power supply for said reader, inclusive.

42. The method of claim 41, wherein said transponder data signal is conditioned with said receiver electronics by rectifying said voltage value of said transponder data signal and integrating said transponder data signal over one or more cycles of a carrier frequency of said transponder data signal.

43. The method of claim 32, wherein said transponder data signal is conditioned with said receiver electronics by rectifying said voltage value of said transponder data signal and integrating said transponder data signal over one or more cycles of a carrier frequency of said transponder data signal.

44. The method of claim 28, further comprising terminating said detection mode and initiating said excitation mode when said proximal transponder is detected.

45. The method of claim 28, wherein said detection mode of operation has a reduced power state and said excitation mode of operation has an increased power state.

46. The method of claim 28, further comprising measuring said declining power level of said internal power source with said analog to digital converter.