METHOD FOR IDENTIFYING A PASSIVE RFID CARD

Abstract

Disclosed is a method for identifying an RFID card as a passive or an active RFID card comprising sending a first RFID command, while keeping an RFID field on; receiving, from the RFID card a corresponding first answering signal; populating a first list with each corresponding first answering signal from the RFID card; sending a second RFID command, wherein the RFID field is paused for a predefined pausing period after sending the second RFID command; receiving, from at least zero active RFID cards, a corresponding second answering signal; populating a second list with each corresponding second answering signal from the at least zero active RFID cards; comparing the entries of the first list with the entries of the second list; identifying each of the at least zero passive RFID cards by having the corresponding first answering signal in the first list but not in the second list.

Claims

1. A method for identifying an RFID card as a passive RFID card or an active RFID card, the method comprising the steps of: sending a first RFID command, while keeping an RFID field on; receiving, from each of at least zero passive RFID cards and at least zero active RFID cards, a corresponding first answering signal; populating a first list with each corresponding first answering signal from the at least zero passive RFID cards and the at least zero active RFID cards; sending a second RFID command, wherein the RFID field is paused for a predefined pausing period after sending the second RFID command; receiving, from the at least zero active RFID cards, a corresponding second answering signal; populating a second list with each corresponding second answering signal from the at least zero active RFID cards; comparing entries of the first list with entries of the second list; identifying each of the at least zero passive RFID cards by having its corresponding first answering signal in the first list but not in the second list.

2. The method of claim 1, further comprising the step of: identifying each of the at least zero active RFID cards by having its corresponding first answering signal both in the first list and in the second list.

3. The method of claim 1, wherein the predefined pausing period is a first period that is specified for unloading an energy of the passive RFID card, the predefined pausing period is a second period that is specified for answering to the second RFID command, and/or the predefined pausing period is long enough to disturb any one of RFID protocol levels.

4. The method of claim 3, wherein the first period is between 50 μs and 10 μs, and the second period is between 5 μs and 0.1 μs.

5. The method of claim 1, wherein the first RFID command and/or the second RFID command is an RFID command according to at least one of NFC-A, NFC-B, NFC-F and NFC-V protocol.

6. The method of claim 1, wherein a wireless charging is only started if exactly zero passive RFID cards are identified, and/or the charging is performed with reduced charging energy.

7. An RFID card identifying device, which is configured to support and/or execute the method according to claim 1.

8. A multiband wireless charging interface comprising an RFID card identifying device according to claim 7.

9. A vehicle comprising a passive RFID card identifying device according to claim 7.

10. (canceled)

11. A non-transitory computer-readable medium containing program instructions, wherein execution of the program instructions by one or more processors of a computing system causes the one or more processors to carry out the method according to claim 1.

12. Distinguishing the passive RFID card from the active RFID card, and preventing the passive RFID card from being damaged by charging, by using the method according to claim 1.

13. The method of claim 4, wherein the second period is about 1 μs.

14. The method of claim 4, wherein the first period is about 20 μs.

15. The method of claim 14, wherein the second period is about 1 μs.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The figures depict:

[0035] FIG. 1a schematically an envelope curve of a sequence of first RFID commands according to an embodiment;

[0036] FIG. 1b schematically an envelope curve of a sequence of second RFID commands according to an embodiment;

[0037] FIG. 2 schematically a section of a first list and a second list according to an embodiment;

[0038] FIG. 3 schematically a vehicle according to an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

[0039] FIG. 1a schematically shows an envelope curve of a sequence of first RFID commands according to an embodiment. The envelope curve has an amplitude A and lasts for a time period shown in the x-axis. It is clearly visible that during sending and after having sent the first RFID command, the RFID field is kept on, i.e. it is, for instance, not stopped or paused immediately after the first RFID command, but the RFID field maintained. The RFID field is kept “on” or is maintained at least for a time period long enough for not disturbing a function and/or a protocol entity of a passive RFID card. Disturbing may comprise any one of the RFID protocol levels. Examples may comprise to interrupt the passive RFID card's energy supply, its clock synchronization, any acknowledgement, and/or another externally recognizable part of an RFID specification.

[0040] FIG. 1b schematically shows an envelope curve of a sequence of second RFID commands according to an embodiment. In contrast to FIG. 1a, the RFID field is paused for a predefined pausing period T1 after sending the second RFID command. The duration of the predefined pausing period may depend on an RFID specification. The time period is at least long enough for disturbing a function of a passive RFID card. When pausing or stopping for a first period T1, as shown, the predefined pausing period is long enough to stop a passive RFID card's power supply, or to make the card reset, no second answering signal can be sent by such a passive RFID card. In contrast, a power disruption for the first period T1 will have no effect on active RFID cards. Thus, passive RFID cards and active RFID cards can be distinguished by an RFID device as described above and/or below.

[0041] Alternatively, pausing may last for a second period T2 (instead of T1, as shown). Interrupting for the second period T2 may cause a different disturbing effect on a passive RFID card. This effect may appear, because a passive RFID card get its clock from an RFID and/or NFC carrier, which is generated by the RFID device, e.g. by the RFID reader. In contrast, active RFID cards run their clock from an internal source. Consequently, disturbing the passive RFID card's clock—either for the first period T1, or for the second period T2—leads to a disturbance or malfunction of an externally recognizable part of an RFID specification. In contrast, the function of active RFID cards is kept unchanged or changed in a way that does not result in a malfunction of an externally recognizable part of an RFID specification. Additionally, or as an alternative, the predefined pausing period is long enough to disturb any one of the RFID protocol levels.

[0042] FIG. 2 schematically shows a section of a first list L1 and a second list L2 according to an embodiment. After sending a first RFID command, while keeping an RFID field on (see FIG. 1a) first answering signals from both the passive RFID cards and the active RFID cards are received, if there are any passive or active RFID cards positioned within an “RFID distance”. In the example shown, five RFID cards are found. The first list L1 shows first answering signals from RFID cards dev1 to dev5. The RFID cards can be distinguished by means of their identifier (or by another unique content). Thus, the entries of the first list L1 comprise the RFID cards' identifier, i.e. “122”, etc. After sending a second RFID command (see FIG. 1b), second answering signals, only from the active RFID cards are received and entered into the second list L2. By comparing the entries of the first list L1 with the entries of the second list L2, each of the at least zero passive RFID cards is identified by having its corresponding first answering signal in the first list L1 but not in the second list L2. By this comparison, dev2 and dev3 are identified as passive RFID cards, because they have their corresponding first answering signal in the first list L1, but not in the second list L2.

[0043] FIG. 3 schematically shows a vehicle 15 according to an embodiment. In the vehicle 15, a multiband wireless charging interface 12, comprising an RFID card identifying device 10, is arranged. Furthermore, three passive RFID cards 20 and one active RFID card 30 are arranged, within the vehicle 15 and within an “RFID distance”. By performing a method as described above and/or below, the RFID cards 20 and 30 can be detected and distinguished the RFID card identifying device 10. This distinguishing may be used for not starting the charging by the multiband wireless charging interface 12, or to reduce the charging energy.