CARD READER DEVICE FOR CONTACTLESS READABLE CARDS AND METHOD FOR OPERATING SAID CARD READER DEVICE
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Accused Products
Abstract
A card reader device is configured to carry out communication with a contactless readable card according to standard ISO/IEC 14443 type B. In order to provide that a modulation index, which self-adjusts in close range in a presence of a contactless readable card, corresponds to a desired specified modulation index, the magnetic field is received and evaluated via a reception antenna of the card reader device. The modulation index is controlled or regulated accordingly in case of deviations between a measured modulation index and a specified value for the modulation index in order to approximate the measured modulation index to the specified value.
34 Citations
41 Claims
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1-20. -20. (canceled)
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21. A method of operating a card reader, which comprises the steps of:
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producing a radio frequency magnetic field in a local area of the card reader, a magnetic field strength of the radio frequency magnetic field is controlled in order to execute communication with a contactlessly readable card, and an information transmission from the card reader to the contactlessly readable card situated in the local area prompts an execution of amplitude shift keying modulation between two non-zero magnetic field strengths, an unmodulated magnetic field strength a and a modulated magnetic field strength b; evaluating the radio frequency magnetic field for detecting and analyzing a variation in the radio frequency magnetic field by the contactlessly readable card situated in the local area; evaluating the radio frequency magnetic field using one of a reception inductor or reception antenna, which is different than a transmission inductor or a transmission antenna that is used, to receive a radio frequency magnetic field signal and ascertaining a modulation index mmeasured, the modulation index mmeasured is formed as a quotient of a difference between the unmodulated magnetic field strength a and the modulated magnetic field strength b and a sum of the two magnetic field strengths a, b (m=(a−
b)/(a+b));comparing the modulation index mmeasured ascertained with a prescribed modulation index mprescribed; and customizing the magnetic field strengths when controlling a production of the radio frequency magnetic field in order to bring the modulation index mmeasured more into line with the prescribed modulation index mprescribed. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29)
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30. A card reader for communicating with a contactlessly readable card in a local area of the card reader, the card reader comprising:
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a controllable transmission unit for producing a radio frequency magnetic field in the local area of the card reader, a magnetic field strength of the radio frequency magnetic field can be controlled to execute communication with the contactlessly readable card, said controllable transmission unit configured to execute amplitude shift keying modulation between two non-zero magnetic field strengths, including an unmodulated magnetic field strength a and a modulated magnetic field strength b, for an information transmission from the card reader to the contactlessly readable card situated in the local area; an evaluation unit for evaluating the radio frequency magnetic field to detect and analyze a variation in the magnetic field by the contactlessly readable card situated in the local area; a reception unit selected from the group consisting of a reception antenna and a reception inductor, which is different than a transmission antenna or a transmission inductor that is used for producing the radio frequency magnetic field, said a reception unit receiving a radio frequency magnetic field signal and linked to said evaluation unit; a control unit; and said evaluation unit having a detection circuit for ascertaining a received magnetic field strength and supplies it to said control unit configured to ascertain a modulation index mmeasured, the modulation index mmeasured being defined as a quotient of a difference between the unmodulated magnetic field strength a and the modulated magnetic field strength b and a sum of the two magnetic field strengths a, b (m=(a−
b)/(a+b)), and to compare an ascertained modulation index mmeasured with a prescribed modulation index mprescribed and to actuate said controllable transmission unit to bring the ascertained modulation index mmeasured more into line with the prescribed modulation index mprescribed. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41)
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Specification