Anti-theft system for a motor vehicle and method for operating the anti-theft system
First Claim
Patent Images
1. An anti-theft system for a motor vehicle, comprising:
- a vehicle-mounted transceiver unit for emitting an interrogation signal, said transceiver unit having an antenna unit emitting a wave having one of an elliptical polarization and a circular polarization and the wave includes the interrogation signal;
a portable code transmitter transmitting back a response signal if said code transmitter receives the interrogation signal; and
a vehicle-mounted evaluation unit receiving and checking an authorization of the response signal and if the response signal provides proper authorization, said evaluation unit one of triggers and enables vehicle-specific functions.
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Abstract
A vehicle-mounted transmitter emits an interrogation code signal in a wave having elliptical or circular polarization. A portable receiver evaluates the received signal only if it receives field components in at least two spatial directions. If the interrogation code signal is accepted by the receiver, a response code signal is transmitted back to the motor vehicle as proof of authorization.
14 Citations
9 Claims
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1. An anti-theft system for a motor vehicle, comprising:
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a vehicle-mounted transceiver unit for emitting an interrogation signal, said transceiver unit having an antenna unit emitting a wave having one of an elliptical polarization and a circular polarization and the wave includes the interrogation signal;
a portable code transmitter transmitting back a response signal if said code transmitter receives the interrogation signal; and
a vehicle-mounted evaluation unit receiving and checking an authorization of the response signal and if the response signal provides proper authorization, said evaluation unit one of triggers and enables vehicle-specific functions. - View Dependent Claims (2, 3)
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4. A method for operating an anti-theft system, which comprises the steps of:
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using a vehicle-mounted transceiver unit for emitting an interrogation signal provided in a wave having one of an elliptical polarization and a circular polarization;
receiving the interrogation signal in a portable code transmitter; and
transmitting back a response signal by the code transmitter only if at least two field components of the interrogation signal which are different in their spatial direction are received. - View Dependent Claims (5, 6)
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7. A method for operating an anti-theft system, which comprises the steps of:
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receiving an interrogation signal in a portable code transmitter and a response signal is subsequently transmitted back as a wave having one of an elliptical polarization and a circular polarization; and
recognizing the response signal as being authorized by a vehicle-mounted transceiver unit only if, at least two field components of the response signal which are different in their spatial direction are received and, a coded information item contained in the response signal corresponds to a coded information item expected by a vehicle-mounted evaluation unit. - View Dependent Claims (8, 9)
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Specification