US 5,412,379 A · Rolling code for a keyless entry system

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.

Claims18

Dependent claims

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.

1 more element

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.

2 more elements

Dependencies are inferred from the claim text.

Rolling code for a keyless entry system

Life of this patent

Rolling code for a keyless entry system

Life of this patent

Abstract

Claims18