Passive keyless entry system

• US 5,515,036 A
• Filed: 01/26/1995
• Issued: 05/07/1996
• 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: Douglas, Daniel G., Gilbert, Lee H., Fraley, Keith D., Kiefer, Richard E., Waraksa, Thomas J.
• Primary Examiner(s): Horabik, Michael
• Application Number:
  US08/378,945
• Time in Patent Office: 467 Days
• Field of Search: 340/825.69, 340/825.72, 340/825.31, 340/457, 307/10.1, 307/10.2, 307/10.5, 361/172, 235/382.5, 375/114, 375/116, 370/18, 370/107, 370/118, 455/127
• US Class Current: 340/12.11
• 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 that is specifically adapted for use with automotive vehicles 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 system includes a portable beacon that is carried by the operator, a receiver/controller located in the vehicle, and an antenna connected to the receiver/controller for receiving the encoded transmission from the beacon. 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.

Claims

1. A keyless entry system for a vehicle comprising:

a portable beacon adapted to be carried by the operator of the vehicle and including transmitter means for transmitting at a predetermined frequency an encoded sinusoidal beacon signal comprising a plurality of data bits identifying said beacon, said beacon signal including a sinusoidal waveform having associated waveform peaks, said beacon further including an antenna drive circuit and a tuned antenna circuit adapted to resonate at said predetermined frequency, said tuned antenna circuit generating the sinusoidal waveform when excited by a drive signal from said antenna drive circuit, said antenna drive circuit providing a pulsed driving signal comprising periodic driving signal pulses interspersed with off periods to said tuned antenna circuit, said driving signal pulses being produced at a predetermined periodic rate related to said predetermined frequency so that the driving signal pulses substantially coincide with the peaks in the beacon signal waveform, and further wherein the duration of the driving signal pulses are substantially less than the off periods between successive driving signal pulses; and

receiver means associated with said vehicle and including antenna means for receiving said beacon signal, signal processing means for decoding said beacon signal to recover said plurality of data bits, and controller means for determining from said plurality of recovered data bits whether said beacon signal corresponds to a valid beacon in activating a predetermined function associated with said vehicle in response thereto.

2. The keyless entry system of claim 1 wherein said signal processing means includes means for creating a signal having a frequency related to said carrier frequency and properly phased with respect to said beacon signal comprising phase lock loop circuit means for locking onto the frequency and phase of said beacon signal when a beacon is within range of said antenna means and sweep circuit means causing the frequency of said phase lock loop circuit means to gradually sweep up and down around a frequency related to said predetermined carried frequency when a beacon is not within range of said antenna means.

3. The keyless entry system of claim 1 wherein said frequency signal is a phase encoded radio frequency signal being transmitted at a single predetermined carrier frequency with the phase of the beacon signal shifted to distinguish between a logical "1" and a logical "0".

4. The keyless entry system of claim 3 wherein said antenna means is tuned to said predetermined carrier frequency to magnetically couple the energy of said beacon signal into said receiver means.

5. The keyless entry system of claim 1 wherein said beacon further includes a portable power source, motion sensing means for sensing physical motion of said beacon, and circuit means responsive to said motion sensing means for activating said transmitter means to transmit said beacon signal.

6. The keyless entry system of claim 1 wherein said predetermined rate is approximately every 1.5 cycles of the frequency beacon signal.

7. The keyless entry system of claim 5 wherein the circuitry in said beacon has a current drain on said portable power source in the microamp range when said beacon is stationary.

8. The keyless entry system of claim 1 wherein said beacon signal includes function information identifying the predetermined function to be performed by said receiver means.

9. The keyless entry system of claim 8 wherein said beacon signal comprises a digital code having a predetermined number of identification and function bits.

10. The keyless entry system of claim 9 wherein said beacon signal further includes an error correction code comprised of a number of bits equal to said predetermined number of identification and function bits.

11. The keyless entry system of claim 10 wherein said beacon signal is Miller encoded.