Passive RF-RF entry system for vehicles

• US 20020024427A1
• Filed: 08/17/2001
• Published: 02/28/2002
• Est. Priority Date: 08/23/2000
• Status: Active Grant

• Current Assignee: Siemens Automotive Corporation (Siemens AG)
• Original Assignee: Siemens Automotive Corporation (Siemens AG)
• Inventors: Banas, Patrick A.
• Granted Patent: US 6,396,412 B1
• Time in Patent Office: Days
• US Class Current: 340/425.5
• CPC Class Codes: B60R 25/246 characterised by the challenge triggering
• CPC Class Codes: G07C 2009/00793 by Hertzian waves
• 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 9/00309 operated with bidirectional data transmission between data carrier and locks

Abstract

A system for preventing unauthorized access to a vehicle having a passive entry system uses a bi-directional radio frequency, or RF-RF, signal. When using a RF-RF signal system, the signal from vehicle to a driver'"'"'s ID device is non-directional and not significantly distance limited. Consequently, a thief may be able to activate the entry system and gain access to the vehicle when the driver'"'"'s ID device is simply within range. The inventive passive entry system interrogates the ID device periodically following parking and locking of the vehicle. The signal strength levels received by the vehicle from the ID device are stored and a signal strength threshold level is computed. Upon a request for entry to the vehicle, a current signal strength level is compared to the signal strength threshold level. Based on that comparison, it is determined whether the request is valid or unauthorized. If the request for entry is deemed unauthorized, then access to the vehicle is not granted.

Claims

1. A passive entry system for a vehicle that uses a bi-directional signal between the vehicle and a passive driver'"'"'s ID device comprising:

a transmitter and receiver on a vehicle, and a transmitter and receiver in a passive driver'"'"'s ID device;

said vehicle being provided with a vehicle lock and a control for said vehicle lock, said transmitter and receiver taking a reference level signal strength of said passive driver'"'"'s ID device at said vehicle transmitter and receiver and storing said threshold value, and when a request occurs for access to said vehicle lock, said vehicle transmitter receiver taking a current signal strength of a passive driver'"'"'s ID device, and comparing said current to said threshold values to determine whether the request is authorized.

2. A passive entry system as recited in claim 1, wherein said passive entry receiver within said vehicle periodically receives measured signal strength levels from the ID device after the vehicle is parked and locked.

3. A passive entry system as recited in claim 2, wherein a passive entry control unit stores the measured signal strength levels and computes a threshold signal strength level based on plural measured signal strength levels.

4. A passive entry system as recited in claim 3, wherein at a point in time when vehicle entry is requested, compares the most recent measured signal strength level to said computed threshold signal strength level to determine whether the request for entry is authorized, and a vehicle lock control which unlocks the vehicle in response to a signal from said passive entry control unit at a point when it has been determined that the request for entry is unauthorized.

5. A passive entry system as recited in claim 1, wherein at the point in time when vehicle entry is requested, if the result of said compared signal strength levels determine that vehicle entry is authorized, then a signal is sent to said vehicle lock control to unlock said vehicle, and if the result of said compared signal strength levels determine that vehicle entry is not authorized, then no signal is sent to said vehicle lock control and said vehicle remains locked.

6. A passive entry system as recited in claim 1, wherein a comparison is factored into said threshold signal strength level to assist in determining whether a request is authorized.

7. A passive entry system as recited in claim 1, wherein said comparison provides an indication of whether a current signal strength indicates the passive driver'"'"'s ID device is closer than at the time of the threshold level, approximately the same distance away, or further away from the vehicle, and this determination is utilized to determine whether a request is authorized.

8. A passive entry system for a vehicle comprising:

a bi-directional radio frequency signal transmitter and receiver on a vehicle and in a passive ID device, said vehicle incorporating a system for preventing unauthorized entry to said vehicle;

said transmitter and receiver within said vehicle periodically receiving measured signal strength levels from the ID device after said vehicle is parked and locked;

a control unit storing the signal strength levels and computes a threshold signal strength level based on said measured signal strength levels;

a device on said vehicle to request entry, said control requesting a current signal level when an entry request is received; and

said current signal level is compared to said computed threshold signal strength level to determine whether the request for entry is authorized, and a vehicle lock control unlocks a vehicle lock in response to a signal from said passive entry control unit at a point when it has been determined that the request for entry is authorized.

9. A passive entry system as recited in claim 8, wherein if the result of said compared signal strength levels determines that vehicle entry is unauthorized, then a signal is not sent to said vehicle lock control to unlock said vehicle.

10. A passive entry system as recited in claim 8, wherein a comparison is factored into said threshold signal strength level to assist in determining whether a request is authorized.

11. A passive entry system as recited in claim 8, wherein said comparison provides an indication of whether a current signal strength indicates the passive driver'"'"'s ID device is closer than at the time of the threshold level, approximately the same distance away, or further away from the vehicle, and this determination is utilized to determine whether a request is authorized.

13. A method for preventing unauthorized access to a vehicle as recited in claim 8 wherein at the point in time when vehicle entry is requested, if the result of said compared signal strength levels determine that vehicle entry is authorized, then a signal is sent to a vehicle lock control to unlock said vehicle.

14. A method for preventing unauthorized access to a vehicle as recited in claim 12, wherein at the point in time when vehicle entry is requested, if the result of said compared signal strength levels determine that vehicle entry is not authorized, then no signal is sent to a vehicle lock control and said vehicle remains locked.

12. A method for preventing unauthorized access to a vehicle having a passive entry system comprising the steps of:

periodically measuring a signal strength level received by a passive entry receiver in the vehicle from a driver'"'"'s ID device after the vehicle is parked and locked;

storing the measured signal strength levels;

computing a threshold signal strength level based on said stored signal strengths; and

at a point in time when vehicle entry is requested, comparing the most recent measured strength level to said computed threshold signal strength level to determine whether the requested entry is authorized and then controlling vehicle entry accordingly.