Transponder detector for an RFID system generating a progression of detection signals

• US 20070236336A1
• Filed: 03/31/2006
• Published: 10/11/2007
• Est. Priority Date: 03/31/2006
• Status: Active Grant

• Current Assignee: Assa Abloy AB
• Original Assignee: Assa Abloy AB
• Inventors: Borcherding, Eric
• Granted Patent: US 8,063,746 B2
• Time in Patent Office: Days
• US Class Current: 340/10.340
• 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 7/10128 the step consisting of detection of the presence of one or more record carriers in the vicinity of the interrogation device
• CPC Class Codes: H04B 5/24 Inductive coupling
• CPC Class Codes: H04B 5/45 Transponders
• CPC Class Codes: H04W 4/80 Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A transponder detector is provided with capabilities for detecting the presence and type of a transponder in its read range while operating at low power. The transponder detector includes an antenna assembly and a detection signal generator circuit coupled to the antenna assembly. The detection signal generator circuit is capable of generating a progression of detection signals on the antenna assembly across a range of frequencies. The transponder detector further includes a response signal receiver circuit coupled to the antenna assembly to receive a progression of response signals from the antenna assembly resulting from the progression of detection signals. A controller is coupled to the response signal receiver circuit which determines the presence and type of the transponder based on an evaluation of a transponder detection parameter in the progression of response signals.

Claims

1. A transponder detector comprising:

an antenna assembly;

a first circuit coupled to said antenna assembly, said first circuit configured to generate and transmit a first detection signal at a first frequency and a second detection signal at a second frequency via said antenna assembly; and

a second circuit coupled to said antenna assembly, said second circuit configured to receive response signals from said antenna assembly resulting from transmission of said first and second detection signals, wherein said response signals have a transponder detection parameter.

2. The transponder detector of claim 1, further comprising a controller configured to detect the presence of a transponder having a transponder frequency in a proximal space of said transponder detector based on said transponder detection parameter.

3. The transponder detector of claim 2, wherein said controller is further configured to determine a transponder type of said detected transponder by comparing said transponder frequency to a known transponder signature.

4. The transponder detector of claim 3, wherein said response signal is an analog signal and said controller includes an analog to digital converter configured to convert said analog signal to a digital signal and to process said digital signal to determine a value of said transponder detection parameter.

5. The transponder detector of claim 1, wherein said transponder detection parameter is a decay rate of said response signal, a voltage of said response signal, or an amount of detection signal energy absorbed by an environment surrounding said antenna assembly.

6. The transponder detector of claim 1, wherein said first circuit comprises a series resistance having a switched series resistor and a resistance switch, said series resistance connected between a ping output signal source and said antenna assembly such that frequency of said detection signals is changeable by controlling positions of said resistance switch.

7. The transponder detector of claim 1, wherein said first circuit comprises a parallel capacitance having a switched parallel capacitor and a capacitance switch, said parallel capacitance connected between a ping output signal source and said antenna assembly such that frequency of said detection signals is changeable by controlling positions of said capacitance switch.

8. The transponder detector of claim 1, wherein said first circuit comprises a series resistance having a switched series resistor and a resistance switch and a parallel capacitance having a switched parallel capacitor and a capacitance switch, said series resistance and parallel capacitance connected between a ping output signal source and said antenna assembly such that frequency of said detection signals is changeable by cooperatively controlling positions of said resistance and capacitance switches.

9. The transponder detector of claim 8, wherein said switched series resistor is a first switched series resistor, said resistance switch is a first resistance switch, said switched parallel capacitor is a first switched parallel capacitor, and said capacitance switch is a first capacitance switch, said series resistance further having a second switched series resistor and a second resistance switch and said parallel capacitance further having second switched parallel capacitor and a second capacitance switch, further wherein frequency of said detection signals is changeable by cooperatively controlling positions of said first and second resistance and capacitance switches.

10. The transponder detector of claim 8, wherein said first circuit generates said first detection signal at said first frequency lower than said second frequency by setting said capacitance switch to a closed position to increase capacitance and setting said resistance switch to an open position to increase resistance.

11. The transponder detector of claim 8, wherein said first circuit generates said second detection signal at said second frequency higher than said first frequency by setting said capacitance switch to an open position to decrease capacitance and setting said resistance switch to a closed position to decrease resistance.

12. A transponder detector comprising:

an antenna assembly;

a first circuit coupled to said antenna assembly and configured to generate and transmit a detection signal progression including a high frequency detection signal at a high frequency, a middle frequency detection signal at a middle frequency and a low frequency detection signal a low frequency via said antenna assembly, wherein said first circuit comprises a series resistance having a first switched series resistor, a first resistance switch, and a second switched series resistor and a second resistance switch, and said first circuit further comprises a parallel capacitance having a first switched parallel capacitor, a first capacitance switch, a second switched parallel capacitor and a second capacitance switch, further wherein said detection signal progression is generated by cooperatively controlling positions of said first and second resistance and capacitance switches; and

a second circuit coupled to said antenna assembly, said second circuit configured to receive a progression of response signals from said antenna assembly, said response signals having a transponder detection parameter.

13. The transponder detector of claim 12, wherein said first circuit generates said low frequency detection signal by setting said first and second capacitance switches to a closed position to create a high level of capacitance and setting said first and second resistance switches to an open position to create a high level of resistance.

14. The transponder detector of claim 12, wherein said first circuit generates said high frequency detection signal by setting said first and second capacitance switches to an open position to create a low level of capacitance and setting said resistance switches to a closed position to create a low level of resistance.

15. The transponder detector of claim 12, wherein said first circuit generates said middle frequency detection signal by setting said first capacitance switch to a closed position and said second capacitance switch to an open position to create a middle level of capacitance and setting said first resistance switch to an open position and said second resistance switch to a closed position to create a middle level of resistance.

16. A frequency ranging method for transponder detection comprising:

transmitting a first detection signal at a first frequency and a second detection signal at a second frequency via an antenna assembly;

receiving a plurality of response signals from said antenna assembly resulting from transmission of said first and second detection signals, wherein said response signals have a transponder detection parameter;

detecting a transponder having a transponder frequency in a proximal space of said antenna assembly based on a change in value of said transponder detection parameter for said response signals.

17. The method of claim 16, further comprising determining a transponder type of said detected transponder by comparing said transponder frequency to a known transponder signature.

18. The method of claim 16, wherein said response signals are analog signals, said method further comprising converting said analog signals to digital signals and processing said digital signals to determine said change in value of said transponder detection signal for said response signals.

19. The method of claim 16, further comprising performing a data transaction with said transponder if said change in value of said transponder detection signal for said response signals reaches or passes a response threshold level.

20. The method of claim 16, further comprising generating said first detection signal at said first frequency lower than said second frequency by selectively increasing capacitance and resistance in a circuit path of a ping signal and generating said second detection signal at said second frequency higher than said first frequency by selectively decreasing said capacitance and resistance in said circuit path of said ping signal.

21. A frequency ranging method for transponder detection comprising:

transmitting a progression of detection signals via an antenna assembly, said progression of detection signals including a high frequency detection signal at a high frequency, a middle frequency detection signal at a middle frequency and a low frequency detection signal a low frequency;

receiving a progression of response signals from said antenna assembly resulting from transmission of said progression of detection signals, wherein said response signals have a transponder detection parameter;

detecting a transponder having a transponder frequency in a proximal space of said antenna assembly based on a change in value of said transponder detection parameter for said progression of response signals.

22. A reader for an RFID system comprising:

a reader antenna assembly;

an excitation signal generator circuit coupled to said reader antenna assembly;

a transponder signal receiver circuit coupled to said reader antenna assembly;

a main controller coupled to said excitation signal generator circuit and said transponder signal receiver circuit; and

a wakeup unit coupled between said reader antenna assembly and said main controller, said wakeup unit configured to generate and transmit a first detection signal at a first frequency and a second detection signal at a second frequency via said reader antenna assembly.

23. The reader of claim 22, wherein said wakeup unit comprises:

a detection signal generator circuit coupled to said reader antenna assembly and configured to generate said first and second detection signals;

a response signal receiver circuit coupled to said reader antenna assembly, said response signal receiver circuit configured to receive a plurality of response signals resulting from transmission of said first and second detection signals on said reader antenna assembly, wherein said response signals have a transponder detection parameter; and

a wakeup controller coupled to said detection signal generator circuit and said response signal receiver circuit, said wakeup controller configured to evaluate a change in value of said transponder detection parameter to detect a transponder in a read range of said reader.

24. The reader of claim 22, wherein said main controller transitions said excitation signal generator circuit and said transponder signal receiver circuit from a low power detection mode to a high power data transaction mode upon detection of said transponder in said read range of said reader,

25. The reader of claim 23, wherein said detection signal generator circuit comprises a series resistance having a switched series resistor and a resistance switch, said series resistance connected between a ping output signal source and said antenna assembly such that frequency of said detection signals is changeable by cooperatively controlling positions of said resistance switch.

26. The reader of claim 23, wherein said detection signal generator circuit comprises a parallel capacitance having a switched parallel capacitor and a capacitance switch, said parallel capacitance connected between a ping output signal source and said antenna assembly such that frequency of said detection signals is changeable by controlling positions of said capacitance switch.

27. A reader for an RFID system comprising:

a reader antenna assembly;

an excitation signal generator circuit coupled to said reader antenna assembly;

a transponder signal receiver circuit coupled to said reader antenna assembly;

a main controller coupled to said excitation signal generator circuit and said transponder signal receiver circuit; and

a detection signal generator circuit coupled to said reader antenna assembly and configured to generate and transmit a detection signal progression including a high frequency detection signal at a high frequency, a middle frequency detection signal at a middle frequency and a low frequency detection signal a low frequency via said antenna assembly, wherein said detection signal generator circuit comprises a series resistance having a first switched series resistor, a first resistance switch, and a second switched series resistor and a second resistance switch, and said detection signal generator circuit further comprises a parallel capacitance having a first switched parallel capacitor, a first capacitance switch, a second switched parallel capacitor and a second capacitance switch, further wherein said detection signal progression is generated by cooperatively controlling positions of said first and second resistance and capacitance switches;

a response signal receiver circuit coupled to said reader antenna assembly, said response signal receiver circuit configured to receive a progression of response signals from said antenna assembly, said response signals having a transponder detection parameter; and

a wakeup controller coupled to said detection signal generator circuit and said response signal receiver circuit, said wakeup controller configured to evaluate a change in value of said transponder detection parameter to detect a transponder in a read range of said reader.

28. The reader of claim 27, wherein said wakeup controller is further configured to determine a type of said transponder detected in said read range of said reader.