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Passive keyless entry system

  • US 20010033222A1
  • Filed: 03/16/2001
  • Published: 10/25/2001
  • Est. Priority Date: 03/20/2000
  • Status: Active Grant
First Claim
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1. An arrangement for a passive keyless entry system comprising a base station arranged on an object to be secured against unauthorized access, for example, a vehicle, and a data carrier (“

  • PKE card”

    ) particularly a chip card which can be carried preferably by an authorized user, and, together with the base station, is adapted to determine authorized access and corresponding control of the base station for exchanging signals with the base station, a signal transmission from the base station to the data carrier being preferably performed by low-frequency, magnetic alternating fields and a signal transmission from the data carrier to the base station being preferably performed by high-frequency, electromagnetic alternating fields (UHF range), in which the base station comprises a first number (N) of LF transmitter stages and an antenna coil associated with each LF transmitter stage for transmitting low-frequency, magnetic alternating fields, and a second number of UHF receiver stages, the data carrier comprises a second number (M) of orthogonally aligned antenna coils each being coupled to an LF receiver stage for receiving low-frequency, magnetic alternating fields, the data carrier further comprises a UHF transmitter stage for transmitting a UHF signal, the base station comprises a third number of UHF receiver stages for receiving the UHF signal transmitted by the UHF transmitter stage of the data carrier, the base station and the data carrier comprise a control stage each for controlling the LF and UHF transmitter and receiver stages and for generating signals to be transmitted and evaluating received signals, first position information about the relative position of the data carrier with respect to the antenna coils of the base station is gained from a measurement of the low-frequency, magnetic alternating fields transmitted by the LF transmitter stages of the base station to the data carrier via the antenna coils of the data carrier in the control stage of the data carrier, which information is transmitted in a preferably encrypted form in the UHF signal from the data carrier to the base station, second position information about the relative position of the data carrier with respect to the UHF receiver stages of the base station is gained from a subsequent measurement of the UHF signal transmitted by the UHF transmitter stage of the data carrier to the base station via the UHF receiver stages of the base station in the control stage of the base station, a signal representing authorized access is generated by comparing both position information components in the control stage of the base station, which signal is only generated when both position information components differ by less than a predetermined extent.

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