Contactless data reception using a cancellation circuit

• US 8,905,310 B2
• Filed: 03/31/2009
• Issued: 12/09/2014
• Est. Priority Date: 03/31/2009
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Kargl, Walter, Ehrlich, Edmund, Emsenhuber, Matthias
• Primary Examiner(s): Lee, Michael G
• Assistant Examiner(s): TARDIF, DAVID P
• Application Number:
  US12/415,070
• Publication Number:
  US 20100243737A1
• Time in Patent Office: 2,079 Days
• Field of Search: 235/439
• US Class Current: 235/439
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 7/10178 including auxiliary means for focusing, repeating or boosting the electromagnetic interrogation field comparable booster antennas integrated on the record carrier itself G06K19/07794
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles
• CPC Class Codes: H04B 5/26 using coils

Abstract

A contactless device including a transmission antenna configured to transmit a transmission signal; a pickup antenna configured to detect a field generated by a pickup signal, which comprises a response signal transmitted from another contactless device and the transmission signal; and a cancellation circuit configured to subtract a voltage of the transmission antenna from a voltage of the pickup antenna.

Claims

1. A contactless card, comprising:

a high-Q transmission antenna configured to transmit a transmission signal;

a broadband pickup antenna configured to detect a field generated by a pickup signal, which comprises a response signal transmitted from a contactless reader and the transmission signal; and

a cancellation circuit configured to subtract in a digital manner a voltage of the high-Q transmission antenna from a voltage of the broadband pickup antenna without subtracting a voltage of the response signal, wherein the cancellation circuit comprises;

a first analog-to-digital converter configured to convert the voltage of the high-Q transmission antenna from analog to digital form; and

a second analog-to-digital converter configured to convert the voltage of the broadband pickup antenna from analog to digital form.

2. The contactless card of claim 1, wherein the cancellation circuit comprises:

a current measuring device configured to measure a current corresponding to the voltage of the high-Q transmission antenna; and

a subtraction device configured to perform the subtraction.

3. The contactless card of claim 2, wherein the cancellation circuit further comprises:

a first amplifier coupled between the current measuring device and the subtraction device, and configured to amplify the voltage of the high-Q transmission antenna; and

a second amplifier coupled between the broadband pickup antenna and the subtraction device, and configured to amplify the voltage of the broadband pickup antenna.

4. The contactless card of claim 2, wherein the current measuring device is a resistor.

5. The contactless card of claim 2, wherein the current measuring device is a capacitor.

6. The contactless card of claim 2, wherein the current measuring device is an inductor.

7. The contactless card of claim 2, wherein the subtraction device is a differential amplifier.

8. The contactless card of claim 1, wherein the broadband pickup antenna is located in the plane of the high-Q transmission antenna.

9. The contactless card of claim 1, wherein the broadband pickup antenna is centered with respect to the high-Q transmission antenna.

10. The contactless card of claim 1, wherein the cancellation circuit comprises:

a voltage measuring device configured to measure the voltage across the high-Q transmission antenna; and

a subtraction device configured to perform the subtraction.

11. The contactless card of claim 10, wherein the voltage measuring device is a capacitive divider.

12. The contactless card of claim 10, wherein the voltage measuring device is a resistive divider.

13. The contactless card of claim 1, further comprising a second pickup antenna configured to detect the transmission signal only.

14. The contactless card of claim 1, wherein the cancellation circuit is configured to perform the subtraction in an analog manner.

15. The contactless card of claim 1, wherein the cancellation circuit performs the subtraction continuously.

16. The contactless card of claim 1, wherein the cancellation circuit performs the subtraction using a static voltage of the high-Q transmission antenna.

17. A contactless communication system comprising:

a contactless reader; and

a contactless card, comprising;

a high-Q transmission antenna configured to transmit a transmission signal;

a broadband pickup antenna configured to detect a field generated by a pickup signal, which comprises a response signal transmitted from the contactless reader, and the transmission signal; and

a cancellation circuit configured to subtract in a digital manner a voltage of the high-Q transmission antenna from a voltage of the broadband pickup antenna without subtracting a voltage of the response signal, wherein the cancellation circuit comprises;

a first analog-to-digital converter configured to convert the voltage of the high-Q transmission antenna from analog to digital form; and

a second analog-to-digital converter configured to convert the voltage of the broadband pickup antenna from analog to digital form.

18. The contactless communication system of claim 17, wherein the contactless reader comprises:

a further transmission antenna configured to transmit a further transmission signal;

a further pickup antenna configured to detect a field generated by a further pickup signal, which comprises a response signal transmitted from the contactless card, and the further transmission signal; and

a further cancellation circuit configured to subtract a voltage of the further transmission antenna from a voltage of the further pickup antenna.

19. A method for detecting a response signal at a contactless card, comprising:

transmitting a transmission signal by a high-Q transmission antenna;

detecting a field generated by a pickup signal, which comprises the response signal transmitted from a contactless reader and the transmission signal, by a broadband pickup antenna; and

subtracting in a digital manner a voltage of the high-Q transmission antenna from a voltage of the broadband pickup antenna without subtracting a voltage of the response signal, wherein the subtracting comprises;

converting the voltage of the high-Q transmission antenna from analog to digital form; and

converting the voltage of the broadband pickup antenna from analog to digital form.

20. The method of claim 19, further comprising measuring the voltage of the high-Q transmission antenna continuously.

21. The method of claim 19, further comprising:

measuring the voltage of the high-Q transmission antenna; and

storing the voltage of the high-Q transmission antenna,

wherein the subtracting step comprises subtracting the stored voltage of the high-Q transmission antenna from the voltage of the broadband pickup antenna.

22. The method of claim 19, further comprising:

converting the voltage of the high-Q transmission antenna from analog to digital form; and

converting the voltage of the broadband pickup antenna from analog to digital form;

wherein the subtraction is performed in a digital manner.

23. A contactless card, comprising:

a high-Q transmission antenna configured to transmit a transmission signal;

a broadband pickup antenna configured to detect a field generated by a pickup signal, which comprises a response signal transmitted from a contactless reader and the transmission signal; and

a cancellation means for subtracting in a digital manner a voltage of the high-Q transmission antenna from a voltage of the broadband pickup antenna without subtracting a voltage of the response signal, wherein the cancellation circuit comprises;

a first analog-to-digital converter configured to convert the voltage of the high-Q transmission antenna from analog to digital form; and

a second analog-to-digital converter configured to convert the voltage of the broadband pickup antenna from analog to digital form.