Security device for guarding a vehicle

• US 7,050,587 B1
• Filed: 08/22/2000
• Issued: 05/23/2006
• Est. Priority Date: 08/31/1999
• Status: Expired due to Fees

• Current Assignee: Continental Automotive GmbH (Continental AG)
• Original Assignee: Mannesmann VDO AG (Continental AG)
• Inventors: Berberich, Reinhold
• Primary Examiner(s): Sheikh, Ayaz
• Assistant Examiner(s): Parthasarathy, Pramila
• Application Number:
  US09/644,390
• Time in Patent Office: 2,100 Days
• Field of Search: 380/262, 340/426.1
• US Class Current: 380/262
• CPC Class Codes: B60R 25/24 using electronic identifiers containing a code not memorised by the user
• CPC Class Codes: G07C 2009/00373 whereby the wake-up circuit is situated in the lock
• CPC Class Codes: G07C 2009/00476 dynamically
• CPC Class Codes: G07C 2009/00531 immobilizer
• CPC Class Codes: G07C 2009/00555 comprising means to detect or avoid relay attacks
• CPC Class Codes: G07C 2009/00793 by Hertzian waves
• CPC Class Codes: G07C 2209/61 Signal comprising different frequencies, e.g. frequency hopping
• CPC Class Codes: G07C 9/00309 operated with bidirectional data transmission between data carrier and locks
• CPC Class Codes: H04Q 9/10 using single different frequencies

Abstract

In a device for actuating a security device, preferably for securing a motor vehicle against unauthorized use, in which a control unit transmits a first coded electromagnetic signal (stimulus signal), in which a portable transmitter (radio key) receives the stimulus signal and transmits a second coded signal (enable signal), and in which the control unit is connected to the security device and actuates the latter if the enable signal is received and recognized, both the control unit and the radio key can after the carrier frequency of the coded electromagnetic signals. During signal transmission, this frequency is altered in a manner which is known only to the control unit and to the radio key.

Claims

1. A device for actuating a security device, preferably for securing a motor vehicle against unauthorized use, comprising:

a control unit for actuating the security device, the control unit having means for transmitting a first coded electromagnetic signal (stimulus signal);

a portable transmitter (radio key) having means for receiving the stimulus signal, and means for transmitting a second coded electromagnetic signal (enable signal) on a carrier frequency determined from the stimulus signal by the radio key; and

wherein the control unit has a receiver tuned to the carrier frequency and actuates the security device if the enable signal is received by the receiver of the control unit and is recognized by the control unit, wherein the control unit and the radio key have means respectively for tuning said receiver of the control unit to said carrier frequency and for altering said carrier frequency of the second coded electromagnetic signal provided by the transmitting means of the radio key; and

wherein the radio key alters said frequency and the control unit correspondingly tunes its receiver during signal transmission in a manner known only to the control unit and to the radio key;

a manner in which the carrier frequency is to be changed is contained in the stimulus signal (1) as a coded information item for transmission to the radio key; and

the stimulus signal (1) contains a random number and the carrier frequencies are determined by applying a cryptoalgorithm (3) to said stimulus signal (1) and, in this context, particularly to the random number contained in the stimulus signal (1); and

wherein the signal transmission takes place over a spectrum of different carrier frequencies and wherein the enable signal contains a coded information item for modulating said spectrum; and

wherein the transmission via different carrier frequencies constitutes frequency hopping.

2. The device as claimed in claim 1, wherein the radio key has a narrowband transmitter, transmission frequency of which is controllable and wherein the radio key alters its transmission frequency over intervals of time when transmitting signals.

3. The device as claimed in claim 2, wherein the tunable receiver of said control unit is a tunable narrowband receiver having the same frequency range as the transmitter in the radio key.

4. The device as claimed in claim 1, wherein selection of the carrier frequency at the receiver and transmitter ends is determined, using a coded information item, which includes said random number, in the stimulus signal, by means of a cryptographic method, operative with said cryptoalgorithm, in the radio key and in the control unit independently of one another.