Method and system for transmitting data for a security system of a motor vehicle
View Patent ↗A method for transmitting data for a security device, in particular for access authorization systems and/or driving authorization systems of a motor vehicle, in which data are transmitted over the air from a transmitter unit to a receiver unit. In a method in which, despite contactless interrogation of the identification signal transmitter, an authorizing access information item cannot be obtained by a third party, the data are transmitted, after capacitive coupling of the transmitter unit and receiver unit, from the transmitter to the receiver using a signal which is generated by a capacitive alternating field.
1. A system for activating and/or deactivating a security device, in particular for access authorization systems and/or driving authorization systems of a motor vehicle, in which system an encoded information item is transmitted over air between a portable transmitter and a receiver, the receiver comparing the received information item with a predefined encoded information item, and outputting a drive signal to the security device when said two information items correspond, wherein the receiver ( 2 ) has a capacitive transmitter unit ( 10 , 11 ) comprising a first capacitor and generates a start signal ( 16 ) by means of an alternating electric field at the first capacitor, a receiver unit ( 13 ) of the transmitter ( 1 ) comprises a second capacitor for reception of the start signal, and transmission of the start signal from the first capacitor to the second capacitor is accomplished by a capacitive coupling between the first and the second capacitors.
2. The system as claimed in claim 1 , wherein, in the capacitive transmitter unit ( 10 , 11 ) of the receiver ( 2 ), the first capacitor ( 10 ) is operated with an alternating current generator ( 11 ), and the second capacitor ( 13 ) receives the signal generated by the transmitter unit ( 10 , 11 ) of the receiver ( 2 ) and passes it on to an evaluation device ( 4 ) of the transmitter ( 1 ).
3. The system as claimed in claim 2 , wherein, after evaluation of the start signal ( 16 ), the evaluation device ( 4 ) generates the encoded information item ( 3 ) which is transmittable from a transmitter unit ( 5 ) of the transmitter ( 1 ) to a receiver unit ( 6 ) of the receiver ( 2 ) by means of inductive coupling or far-field coupling.
4. The system as claimed in claim 1 , wherein the encoded information item ( 3 ) is modulated onto a high-frequency carrier frequency which is generated by an alternating current generator ( 11 ).
5. The system as claimed in claim 2 , wherein the first capacitor ( 10 ) is formed between an outer shell ( 15 ) of an access device and an activation device ( 12 ) which is arranged on the outer shell of the access device.
6. The system as claimed in claim 2 , wherein the first capacitor ( 10 ) is formed between bodywork of the vehicle and a control element which is arranged in the interior of the motor vehicle.
7. The system as claimed in claim 5 , wherein, when the activation device ( 12 ) is touched by the user, the signal which is to be detected by the second capacitor ( 13 ) is amplified.
8. The system as claimed in claim 6 , wherein, when the control element is touched by the user, the signal which is to be detected by the second capacitor ( 13 ) is amplified.