Communications: electrical – Land vehicle alarms or indicators – Of burglary or unauthorized use
Reexamination Certificate
1999-03-05
2001-04-03
Hofsass, Jeffery (Department: 2632)
Communications: electrical
Land vehicle alarms or indicators
Of burglary or unauthorized use
C340S430000, C340S425500, C340S428000, C340S539230, C340S870030, C340S870030
Reexamination Certificate
active
06211776
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for initializing an anti-theft system for a motor vehicle. The anti-theft system has a transceiver unit disposed in the motor vehicle that transmits interrogation signals via an antenna. The interrogation signals are received by a portable response transmitter which in turn responds by transmitting a response signal back to the transceiver. The transceiver in turn evaluates the response signal.
A known anti-theft system has an antenna device in the driver's door and is described in Published, Non-Prosecuted German Patent Application DE 38 20 248 A1. If a user wishes to get into the vehicle, an interrogation/response dialog is triggered by activating a trigger circuit. In the process, an interrogation signal is transmitted by the antenna device in the vehicle to a response transmitter carried by the user. The response transmitter transmits back an encrypted response signal if it receives the interrogation signal. In the motor vehicle, the response signal is compared with an expected setpoint signal and if the two correspond (successful authentication), the doors are locked or unlocked.
The same interrogation/response dialog also takes place in the motor vehicle when the user wishes to start the vehicle. After the ignition switch is activated, an interrogation signal is emitted and a response signal is subsequently transmitted back. If the response signal is authorized, the immobilizer is deactivated.
In such an anti-theft system, the range of the interrogation signal may be too low, so that the response transmitter cannot receive the interrogation signal. The range of the interrogation signal may also be too large and other response transmitters located in the vicinity may be addressed in error (overshoot). When attempting to release the immobilizer it is particularly important that only one response transmitter in the vicinity of the vehicle or in the interior of the vehicle is addressed, even if the response transmitter is stored, for example, far from the ignition lock in the side compartment in the interior of the vehicle. If the response transmitter cannot receive the interrogation signal, the user cannot get into his motor vehicle and cannot start his motor vehicle either.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for initializing an anti-theft system for a motor vehicle that overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, in which signals are emitted by a vehicle-mounted transmitter, while the anti-theft system is operating, such that the signals can reliably be received by a portable response transmitter located at a defined distance from the motor vehicle.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for initializing an anti-theft system, which includes: a) setting an initial transmit condition; b) emitting an interrogation signal via a transceiver unit disposed in a motor vehicle and electrically connected to at least one antenna disposed on the motor vehicle; c) receiving the interrogation signal in a portable response transmitter located at a previously defined fixed position and emitting a response signal in response to the interrogation signal; d) receiving, evaluating, and comparing the response signal in a control unit of the transceiver unit with setpoint values; e) changing the initial transmit condition according to a predefined algorithm in dependence on the response signal received; and f) repeating steps b)-e) until the portable response transmitter just still receives the interrogation signal or just fails to receive the interrogation signal any more.
During the initialization, a transceiver unit repeatedly emits an interrogation signal systematically according to a predefined algorithm with changed transmit conditions until the response transmitter just still receives an interrogation signal. If the position of the response transmitter is fixed during the initialization, the maximum range of the signals can thus reliably be set precisely in accordance with the immediate area outside the vehicle or to the passenger compartment of the vehicle. In this way, the response transmitter reliably receives the interrogation signal as soon as it is located in the vicinity of the motor vehicle or within the motor vehicle.
The transmit conditions under which, given the setting conditions during the initialization, a response signal is just still received by the transceiver unit can thus be stored, as future transmit conditions, in a memory. Interrogation signals are emitted at a later time using these transmit conditions. The transmit power of the transmitter in the transceiver unit, on the basis of which the range of the signals is determined, is preferably used as transmit conditions.
The antennas that are used are electrical coils that are disposed distributed on or in the motor vehicle. As a result, individual antennas do not need an excessively large transmit power. During the initialization, the transmit conditions can be changed incrementally or continuously within a predefined range until the response transmitter just still receives the interrogation signal. As a result, the correct transmit conditions are determined quickly. Each response transmitter can emit a code together with the response signal, as a result of which the transmit condition which has just been set can be assigned to the code. As a result, the transceiver unit knows the transmit conditions for each response transmitter.
The response transmitter can also have a measuring device with which the received transmit power is measured. The power can be transmitted, as a measured value, back to the transceiver unit in the motor vehicle. As a result, from the measured power the transceiver unit can calculate how the transmit conditions are to be changed so that the response transmitter just still receives an interrogation signal.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method for initializing an anti-theft system for a motor vehicle, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
REFERENCES:
patent: 5815087 (1998-09-01), Campbell et al.
patent: 5966083 (1999-10-01), Marsh et al.
patent: 6064296 (2000-05-01), Clancy et al.
patent: 6100603 (2000-08-01), Gold
patent: 3820248A1 (1989-01-01), None
Glehr Manfred
Rohrl Thomas
Greenberg Laurence A.
Hofsass Jeffery
Lerner Herbert L.
Nguyen Hung
Siemens Aktiengesellschaft
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