Rolling code for a keyless entry system

• US 5,412,379 A
• Filed: 05/18/1992
• Issued: 05/02/1995
• Est. Priority Date: 05/27/1988
• Status: Expired due to Term

• Current Assignee: Quintras Foundation AG LLC (Intellectual Ventures LLC)
• Original Assignee: Lectron Products Incorporated
• Inventors: Slaughter, Sherri A., Poirier, James A., Rea, Irvin B., Michaels, Paul A., Waraksa, Thomas J.
• Primary Examiner(s): Horabik, Michael
• Application Number:
  US07/885,624
• Time in Patent Office: 1,079 Days
• Field of Search: 340/825.31, 340/825.69, 340/825.72, 307/10.2, 361/172, 180/287
• US Class Current: 340/5.26
• CPC Class Codes: B60R 25/24 using electronic identifiers containing a code not memorised by the user
• CPC Class Codes: G07C 2009/0023 with encription of the transmittted data signal
• CPC Class Codes: G07C 2009/00246 periodically, e.g. after a time period
• CPC Class Codes: G07C 2009/00793 by Hertzian waves
• CPC Class Codes: G07C 2009/0096 Electronic keys comprising a non-biometric sensor
• CPC Class Codes: G07C 2209/63 Comprising locating means for detecting the position of the data carrier, i.e. within the vehicle or within a certain distance from the vehicle
• CPC Class Codes: G07C 9/00182 operated with unidirectional data transmission between data carrier and locks
• CPC Class Codes: H04L 7/041 using special codes as synchronising signal

Abstract

A passive keyless entry system is specifically adapted for use with automotive vehicles. The system includes a portable beacon that is carried by a vehicle operator, a receiver/controller located in the vehicle, and an antenna connected to the receiver/controller for receiving an encoded transmission from the beacon. The system is designed to automatically unlock the vehicle as the operator approaches the vehicle. The system is further designed to automatically lock the vehicle as the operator, carrying the beacon, moves away from the vehicle. The beacon includes a motion sensor to conserve battery life when the beacon is stationary. Transmission between the beacon and the receiver/controller is characterized by a magnetically coupled radio frequency signal embodying differential phase encoded data with error correction coding of the data to enhance noise immunity and signal discrimination. In addition, the transmitted signal between the beacon and the receiver is continually changing in order to deter theft. A clock in the receiver/controller is automatically reset to a clock code of the encoded transmission if the transmitted signal is valid.

Claims

1. A keyless entry system for gaining entry to a vehicle, comprising:

a portable beacon including a transmitter for transmitting a coded beacon signal, a beacon clock circuit for producing a beacon clock code that is continually changing at a predetermined rate, and code generation means for producing said coded beacon signal in accordance with said beacon clock code such that the content of said coded beacon signal continually changes;

a receiver associated with the vehicle, said receiver including an antenna for receiving said coded beacon signal when said beacon is within a predetermined range; and

controller means for decoding said coded beacon signal and activating a first predetermined function associated with the vehicle upon receipt of a valid coded beacon signal from the beacon, said controller means including means for updating a receiver clock code at substantially said predetermined rate to coincide with the changing beacon clock code.

2. The keyless entry system of claim 1 wherein the controller means activates a second predetermined function associated with the vehicle when said beacon is removed from the predetermined range and said receiver stops receiving the coded beacon signal.

3. The keyless entry system of claim 1 wherein the transmitter transmits a coded beacon signal including a beacon identification code and a beacon clock code, wherein the beacon clock code changes at the predetermined rate and wherein the controller means separates the beacon identification code from the beacon clock code to determine a valid transmitted signal.

4. The keyless entry system of claim 3 wherein the beacon includes first storage means for storing an initial beacon clock code, second storage means for storing a constant value and a counter means for counting beacon clock pulses, said counter means emitting an interrupt signal every predetermined number of clock pulses to set the predetermined interval at which the beacon signal is changing by instructing the second storage means to add the constant value to the initial beacon clock code in order to produce an updated beacon clock code wherein the updated beacon clock code is updated by the constant value each time the counter means emits the interrupt signal.

5. The keyless entry system of claim 4 wherein the updated clock code is applied to a logic gate along with the beacon identification code and the output of the logic gate is scrambled to be transmitted as at least part of the coded beacon signal.

6. The keyless entry system of claim 4 wherein the counter means emits the interrupt signal approximately every five seconds.

7. The keyless entry system of claim 1 wherein the controller means includes first storage means for storing an identification code associated with the beacon and second storage means for storing the receiver clock code , said controller means separating a beacon identification code and a beacon clock code from the coded beacon signal and comparing them to the identification code in the first storage means and the receiver clock code in the second storage means to determine a valid beacon signal.

8. The keyless entry system of claim 7 wherein the controller means further includes tolerance means for generating a variable tolerance between the beacon clock code and the receiver clock code such that the controller means will determine that the beacon signal is valid for a wider range of acceptable errors as the time between accepted valid beacon signals by the receiver increases.

9. The keyless entry system of claim 7 wherein the controller means include storage means for storing the beacon identification code and the beacon clock code, and wherein the beacon clock code is updated in the storage means upon receipt of a valid beacon signal.

10. The keyless entry system of claim 9 wherein the storage means stores a plurality of beacon identification codes and beacon clock codes.

11. The keyless entry system of claim 1 wherein said beacon includes at least one function switch, said function switch activating a second predetermined function associated with the vehicle.

12. A method of performing predetermined functions associated with a vehicle, said method comprising the steps of:

transmitting a coded signal from a portable transmitter to a receiver associated with the vehicle, said step of transmitting a coded signal including transmitting a coded signal that includes a transmitter identification code and a transmitter clock code;

decoding the coded transmitted signal in the receiver to determine if the coded signal is a valid signal and performing a vehicle function if the coded signal is valid;

altering the coded signal in the transmitter at predetermined intervals in order to transmit an updated coded signal that changes with time at a predetermined rate, said step of altering the coded signal including continually updating the transmitter clock code with respect to a transmitter clock at the predetermined intervals, said step of updating the transmitter clock code including Updating the transmitter clock code by adding a constant value to an initial clock code to produce an updated clock code and continuously adding the constant to the updated clock code to form subsequent updated clock codes after each of said predetermined intervals; and

updating a clock in the receiver in order to coincide with the updated coded signal.

13. The method according to claim 12 wherein the step of updating the clock code includes applying the clock code to a logic gate along with the identification code in order to produce a combined clock code and identification code as at least part of the coded signal.

14. The method according to claim 13 wherein the step of producing a combined clock code and identification code includes scrambling the combined clock code and identification code in a random fashion.

15. The method according to claim 12 wherein the step of decoding the coded signal includes the steps of separating the transmitter identification code and the transmitter clock code from the coded signal in the receiver, comparing the transmitter identification code with a stored identification code in the receiver, and comparing the transmitter clock code with a stored clock code in the receiver.

16. The method according to claim 15 wherein the step of decoding the coded signal includes the step of generating a tolerance factor in the receiver for enabling discrepancies between the transmitted coded signal and the receiver clock code to increase over time between accepted valid transmitted signals and still indicate that the transmitted coded signal is valid.

17. The method according to claim 15 wherein the step of comparing the transmitter clock code with the receiver clock code includes updating the receiver clock code to coincide with the transmitter clock code upon receipt of a valid transmitted signal.

18. A keyless entry system for gaining entry to a vehicle, said entry system comprising:

a portable beacon including a transmitter for transmitting a coded beacon signal, said transmitter including a first register and a second register, said coded beacon signal being generated at least in part by combining a digital data word stored in the first register with a digital data word stored in the second register, wherein the data word stored in the first register is changed at different points in time such that the generated coded beacon signal is changed accordingly; and

a receiver associated with the vehicle, said receiver including an antenna for receiving said coded beacon signal when said beacon is within a predetermined range of the receiver, said receiver further including a controller means for decoding said beacon signal and activating a first predetermined function associated with the vehicle upon receipt of a valid coded beacon signal from the beacon, said controller means including means for updating a receiver memory at substantially the same points in time as the data word stored in the first register is changed to coincide with the changing data word in the first register of the beacon.