GB2306031A - Anti-theft device for a motor vehicle - Google Patents

Anti-theft device for a motor vehicle Download PDF

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Publication number
GB2306031A
GB2306031A GB9620386A GB9620386A GB2306031A GB 2306031 A GB2306031 A GB 2306031A GB 9620386 A GB9620386 A GB 9620386A GB 9620386 A GB9620386 A GB 9620386A GB 2306031 A GB2306031 A GB 2306031A
Authority
GB
United Kingdom
Prior art keywords
signal
radio
intermediate frequency
theft device
demodulator
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB9620386A
Other versions
GB9620386D0 (en
GB2306031B (en
Inventor
Claus Peter
Bernhard Foerstl
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
Original Assignee
Siemens AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens AG filed Critical Siemens AG
Publication of GB9620386D0 publication Critical patent/GB9620386D0/en
Publication of GB2306031A publication Critical patent/GB2306031A/en
Application granted granted Critical
Publication of GB2306031B publication Critical patent/GB2306031B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G07—CHECKING-DEVICES
    • G07C—TIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE
    • G07C9/00—Individual registration on entry or exit
    • G07C9/00174—Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys
    • G07C9/00182—Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys operated with unidirectional data transmission between data carrier and locks
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R25/00—Fittings or systems for preventing or indicating unauthorised use or theft of vehicles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60R—VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR
    • B60R25/00—Fittings or systems for preventing or indicating unauthorised use or theft of vehicles
    • B60R25/01—Fittings or systems for preventing or indicating unauthorised use or theft of vehicles operating on vehicle systems or fittings, e.g. on doors, seats or windscreens
    • B60R25/04—Fittings or systems for preventing or indicating unauthorised use or theft of vehicles operating on vehicle systems or fittings, e.g. on doors, seats or windscreens operating on the propulsion system, e.g. engine or drive motor
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/27—Adaptation for use in or on movable bodies
    • H01Q1/32—Adaptation for use in or on road or rail vehicles
    • H01Q1/3208—Adaptation for use in or on road or rail vehicles characterised by the application wherein the antenna is used
    • H01Q1/3233—Adaptation for use in or on road or rail vehicles characterised by the application wherein the antenna is used particular used as part of a sensor or in a security system, e.g. for automotive radar, navigation systems
    • H01Q1/3241—Adaptation for use in or on road or rail vehicles characterised by the application wherein the antenna is used particular used as part of a sensor or in a security system, e.g. for automotive radar, navigation systems particular used in keyless entry systems
    • G—PHYSICS
    • G07—CHECKING-DEVICES
    • G07C—TIME OR ATTENDANCE REGISTERS; REGISTERING OR INDICATING THE WORKING OF MACHINES; GENERATING RANDOM NUMBERS; VOTING OR LOTTERY APPARATUS; ARRANGEMENTS, SYSTEMS OR APPARATUS FOR CHECKING NOT PROVIDED FOR ELSEWHERE
    • G07C9/00—Individual registration on entry or exit
    • G07C9/00174—Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys
    • G07C2009/00753—Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys operated by active electrical keys
    • G07C2009/00769—Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys operated by active electrical keys with data transmission performed by wireless means
    • G07C2009/00793—Electronically operated locks; Circuits therefor; Nonmechanical keys therefor, e.g. passive or active electrical keys or other data carriers without mechanical keys operated by active electrical keys with data transmission performed by wireless means by Hertzian waves
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/16—Circuits

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Security & Cryptography (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Burglar Alarm Systems (AREA)
  • Lock And Its Accessories (AREA)

Description

4-g 2306031 Anti-theft device for a motor vehicle The invention relates to
an anti-theft device for a motor vehicle, with the aid of which an unauthorised user is prevented from gaining access to the vehicle, or the vehicle is prevented from moving.
is A known anti-theft device (EP 0 138 090 A2) has a portable transmitter which is arranged in a key and which transmits an identification signal. A receiving antenna is arranged in a side mirror. It receives the identification signal and conveys it to a receiving unit. A comparator compares the identification signal with a permanently stored desired signal and generates a control signal when the two signals correspond. Independently of the control signal an electrical actuator acts on a closing device.
The receiving antenna is additionally built into the motor vehicle and provided with separate connecting lines to the receiving unit.
Another known anti-theft device (DE 295 08 903 U1) has a radio receiver which, by means of an antenna, can receive a radio signal transmitted via a transmission installation. The antenna can be mounted on the motor vehicle as an external antenna or may be an integrated component of the radio receiver. on receiving the appropriate radio signal the radio receiver generates a receiving signal which is conveyed to a control circuit. The control circuit is connected to three s'tch means which are each assigned to a circuit of wi the motor vehicle to be secured, and either close or open the respective circuit independently of the receiving signal.
Embodiments of the invent-ion may provide an anti-theft device which is simple and is constructed without additional connecting lines.
is According to the invention there is thus provided an anti-theft device for a motor vehicle having a radio, having: a transmitter which generates and transmits an identification signal, a receiving antenna which receives the identification signal and conveys it to an evaluation unit, the evaluation unit which converts the identification signal into a code signal, a control device which compares the code signal with a desired code signal and, when the two signals correspond, generates a control signal, and a safety unit which is controlled in dependence on the control signal, wherein the receiving antenna is the antenna of the car radio, the evaluation unit has a filter device and a demodulator device, the already existing intermediate frequency filter of the car radio is used as the filter device, and the already existing demodulator of the car radio is used as the demodulator device.
Preferred embodiments of the invention are characterised in the subclaims.
Exemplary embodiments of the invention are explained in detail below with reference to the schematic drawing. The Figure shows a block diagram of an anti-theft device of the invention.
An anti-theft device for a motor vehicle has a transmitter 1 and a receiving antenna. By operating a key, a binary code signal is generated in the transmitter 1, modulated with a high frequency carrier signal and transmitted as an identification signal.
The receiving antenna receives the identification signal and conveys it to an evaluation unit 2. In evaluation unit 2 the identification signal is converted into the code signal.
is The anti-theft device also has a control device 3 which contains a comparison device. In the comparison device the code signal is compared with a desired code signal stored there.
A so-called alternating code or a fixed code can be used to generate the code signal and the desired code signal. With a fixed code, the code signal and desired code signal are the same each time the transmitter 1 is operated and the code signal is received. with an alternating code, the code signal and desired code signal are changed with the aid of a mathematical algorithm each time the transmitter is operated and the code signal is received.
When the code signal corresponds with the desired code signal a control signal is produced by the control device 3.
A safety unit 4 in the motor vehicle is controlled from the control device 3 by means of the control signal. The safety unit 4 may be a door- locking mechanism or a so-called immobiliser.
The term,immobiliser" means those electronic devices in the motor vehicle which make starting of the engine possible only with an authorised release. So, for instance, the engine control device, an on/off valve of the fuel line, or a switch in the ignition circuit can be released by the control device.
is In motor vehicles there is usually an antenna 5 (called the radio antenna below) for receiving radio signals for the car radio 6. The radio antenna 5 is also designed to receive high-frequency signals since radio signals in the long wave to ultra short wave range can be transmitted and received.
According to the exemplary embodiment, the radio antenna 5 is used as a receiving antenna in the antitheft device. No structural change therefore has to be made to the radio antenna 5 in order to receive the highfrequency identification signal.
The evaluation unit 2 is connected to the radio antenna 5, in that an already existing electrical connection between the radio antenna 5 and the car radio 6 is used. In the region of the car radio 6 this connection has a branch to the evaluation unit 2.
The separate receiving antenna and parts of the specific electrical connection between the evaluation unit 2 and the radio antenna 5 are therefore omitted in the anti-theft device.
For car radios 6 the sufficiently well-known superheterodyne principle is applied and will be described briefly below. Car radios which are constructed in accordance with the superheterodyne principle have an input filter 7, a mixing stage 8 and a local oscillator 9.
Signals, whose frequencies lie outside the frequency range of the radio signals, are suppressed by the input filter 7 because it is designed as a wide-band band pass filter.
is In the mixing stage 8 a received radio signal is multiplied with a mixing signal which is generated by the local oscillator 9 and whose frequency is the oscillator frequency. The mixing signal has a frequency which is approximately equal to the difference between the frequency of a carrier signal of a radio frequency and that of an intermediate frequency.
In the mixing stage 8 the radio signal is converted in its frequency state in such a way that the frequency of the carrier signal becomes the intermediate frequency. This means that irrespective of the frequency of the carrier signal at the output of the mixing stage 8 the radio signal has the intermediate frequency.
An intermediate frequency filter 10 is connected to the mixing stage 8 and is designed as a band pass filter in such a way that only frequencies which are in a narrow frequency band around the intermediate frequency are allowed through.
The radio signal is demodulated by a subsequently connected demodulator 11, and conveyed to a driver 12 which amplifies the radio signal and conveys it to a loud speaker.
The superheterodyne principle is also used for the evaluation unit 2 of the anti-theft device. So, for the evaluation unit 2 of the anti-theft device the intermediate frequency filter 10 and the demodulator 11 of the car radio 6 is are used. This leads to a simplification of the anti-theft device as already available equipment in the car radio 6 is used.
In addition, the evaluation unit 2 also has a switching is device 13 in which are arranged an input switch 14 and an output switch 15. In its ON state, the input switch 14 joins the radio antenna to a conversion device 16. The output switch 15 joins the conversion device 16 in its ON state to the intermediate frequency filter 10.
The input and the output switches 14, 15 are in their ON state as long as the,ignition switch is switched off. Hence the identification signal is only conveyed to the anti-theft device when the ignition switch is switched off. The identification signal is then conveyed from the radio antenna 5 via a connecting line to the conversion device 16 which has a pre-filter 17, an oscillator 18 and a multiplier 19.
The pre-filter 17 filters out high-frequency interference in the identification signal. The oscillator 18 generates a multiplier signal whose frequency is approximately equal to the difference between the frequency of the identification signal and the intermediate frequency. The identification signal is converted by the multiplier 19 into an intermediate frequency signal by multiplication with the multiplier signal, and conveyed to the intermediate frequency filter 10.
By means of the conversion device 16 the identification signal is converted in its frequency so that it has the same carrier frequency as the radio signal after the mixing stage 8.
When the ignition switch is switched off, the demodulator 11 and the intermediate frequency filter 10 are supplied with energy independently of the energy supply of the car radio 6.
is The intermediate frequency filter 10 filters out interfering signal components in secondary frequency bands of the intermediate frequency signal which are generated by multiplication of the identification signal with the mixing signal.
The demodulator 11 demodulates the intermediate frequency signal and thus obtains the code signal. It is not significant to the invention whether the intermediate frequency signal is an amplitude-modulated or a frequency-modulated signal.
A signal preparation unit 20, from which square-wave signals with high side steepness are generated out of the demodulated signal, can be disposed between the demodulator 11 and the control device 3. The loss of side steepness can thus be compensated for by the low quality factor demodulator 11. A high side steepness is required by the control device 3 for correct processing of the code signal.
The control device 3 may also have a microprocessor which compares the code signal with the desired code signal and in the case of an alternating code also generates the desired code signal. Moreover, the microprocessor can also take over control functions, such as control of the switching device 13.
In a preferred embodiment of the invention the input filter 7, the mixing stage 8 and the local oscillator 9 of the car radio 6 are used for the conversion device 16, thus simplifying the anti-theft device since already existing parts of the car radio 6 are used.
The input filter 7 then has to be designed so that it lets through the frequency of the identification signal. The local oscillator 9 is then designed so that the oscillator frequency can be controlled by the control device 3 in such a way that it is approximately equal to the difference between the frequency of the identification signal and the intermediate frequency.
The switching device 13 is then omitted since the local oscillator 9 is controlled by the control device 3 in such a way that the identification signal in the mixing stage 8 is converted to the intermediate frequency when the ignition switch is switched off.
In one design example of the invention the identification signal has a carrier frequency of approximately 434 Mhz and the intermediate frequency is about 11 Mhz. Accordingly, the frequency of the multiplier signal is 423 Mhz. The intermediate frequency filter 10 has as a band pass a mean frequency of about 11 Mhz and a band width of about 10 Khz.
1

Claims (6)

Claims
1. Anti-theft device for a motor vehicle having a radio, having:
- a transmitter (1) which generates and transmits an identification signal - a receiving antenna which receives the identification signal and conveys it to an evaluation unit (2), the evaluation unit (2) which converts the identification signal into a code signal, - a control device (3) which compares the code signal with a desired code signal and, when the two signals correspond, generates a control signal, and is - a safety unit (4) which is controlled in dependence on the control signal, wherein - the receiving antenna is the antenna (5) of the car radio the evaluation unit (2) has a filter device and a demodulator device, the already existing intermediate frequency filter (10) of the car radio (6) is used as the filter device, and the already existing demodulator (11) of the car radio (6) is used as the demodulator device.
2. Anti-theft device according to claim 1, wherein the evaluation unit (2) has a conversion device (16) which converts the identification signal by converting the frequency into an intermediate frequency signal, the conversion device (16) is connected to the filter device which filters the intermediate frequency signal, and the demodulator device which demodulates the intermediate frequency signal into the code signal is connected to the filter device.
is
3. Anti-theft device according to claim 2, wherein the conversion device (16), having the antenna (5) and the demodulator device, is electrically connected as long as an ignition switch is switched off.
4. An anti-theft device for a vehicle, substantially as hereinbefore described with reference to the accompanying drawing
5. A vehicle having an anti-theft device according to any preceding claim.
6. A car radio when connected to form part of the anti-theft device of any one of claims 1 to 4.
GB9620386A 1995-10-09 1996-09-30 Anti-theft device for a motor vehicle Expired - Fee Related GB2306031B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE1995137609 DE19537609C1 (en) 1995-10-09 1995-10-09 Anti-theft device for a motor vehicle

Publications (3)

Publication Number Publication Date
GB9620386D0 GB9620386D0 (en) 1996-11-13
GB2306031A true GB2306031A (en) 1997-04-23
GB2306031B GB2306031B (en) 1997-10-08

Family

ID=7774417

Family Applications (1)

Application Number Title Priority Date Filing Date
GB9620386A Expired - Fee Related GB2306031B (en) 1995-10-09 1996-09-30 Anti-theft device for a motor vehicle

Country Status (3)

Country Link
DE (1) DE19537609C1 (en)
FR (1) FR2739603A1 (en)
GB (1) GB2306031B (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2389997A (en) * 2002-05-23 2003-12-24 Visteon Global Tech Inc Wireless radio transmission system for vehicle using earth connection as antenna

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19731736C1 (en) 1997-07-23 1998-07-23 Siemens Ag Remote controlled theft protection system for motor vehicle
WO1999065743A1 (en) * 1998-06-18 1999-12-23 Lear Corporation Vehicle communication system having integrated radio and remote signal antenna
DE10016413B4 (en) * 2000-04-01 2006-02-02 Robert Bosch Gmbh Circuit arrangement and method for transmitting and / or receiving a vehicle safety system
DE10149276A1 (en) * 2001-10-05 2003-04-24 Siemens Ag Anti-theft system, method for operating an anti-theft system and components of an anti-theft system
DE10215884A1 (en) * 2002-04-11 2003-10-23 Volkswagen Ag Vehicle antenna change over device has device for switching first or second input terminal to output terminal, controller for driving switching device on basis of activity signal from vehicle device
DE10341199A1 (en) * 2003-09-04 2005-04-07 Hirschmann Electronics Gmbh & Co. Kg Apparatus for receiving signals to control a function in a vehicle

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4835531A (en) * 1986-05-16 1989-05-30 Alps Electric Co. Ltd. Automobile remote-control system

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6064537A (en) * 1983-09-19 1985-04-13 Nissan Motor Co Ltd On-vehicle radio transmitter using induced electromagnetic field as medium
DE29508903U1 (en) * 1995-05-30 1995-08-17 Hahn G Uwe Anti-theft device for vehicles

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4835531A (en) * 1986-05-16 1989-05-30 Alps Electric Co. Ltd. Automobile remote-control system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2389997A (en) * 2002-05-23 2003-12-24 Visteon Global Tech Inc Wireless radio transmission system for vehicle using earth connection as antenna
GB2389997B (en) * 2002-05-23 2004-06-23 Visteon Global Tech Inc Radio data wireless transmission system for an automotive vehicle
US7161471B2 (en) 2002-05-23 2007-01-09 Visteon Global Technologies, Inc. System for an automotive vehicle

Also Published As

Publication number Publication date
GB9620386D0 (en) 1996-11-13
GB2306031B (en) 1997-10-08
FR2739603A1 (en) 1997-04-11
DE19537609C1 (en) 1997-03-13

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Date Code Title Description
PCNP Patent ceased through non-payment of renewal fee

Effective date: 20000930