PASSIVE ENTRY SYSTEM AND METHOD FOR A VEHICLE

• US 20110148573A1
• Filed: 12/22/2009
• Published: 06/23/2011
• Est. Priority Date: 12/22/2009
• Status: Active Grant

• Current Assignee: Lear Corporation
• Original Assignee: Lear Corporation
• Inventors: Girard, Hilton W. (Jerry) III, Ghabra, Riad, Yakovenko, Nikolay
• Granted Patent: US 8,284,020 B2
• Time in Patent Office: Days
• US Class Current: 340/5.61
• CPC Class Codes: B60R 25/245 where the antenna reception area plays a role
• CPC Class Codes: H04B 17/24 with feedback of measurements to the transmitter
• CPC Class Codes: H04B 17/27 for locating or positioning the transmitter
• CPC Class Codes: H04B 17/318 Received signal strength

Abstract

A passive entry system and method for determining the location of a remote transmitter positioned near a vehicle. The system and method may include an irregularly shaped authorization zone. The authorization zone may be formed using as least three LF antennas. Alternatively, at least two antennas may be used to form at least one elliptically shaped authorization zone. A controller may determine the location of the fob when the fob is physically positioned within the authorization zone.

Claims

1. A method for determining the location of a remote transmitter positioned about a vehicle, the method comprising:

transmitting a measuring signal from a first antenna located about the vehicle to a remote transmitter;

receiving an acknowledgement signal from the remote transmitter in response to the measuring signal, wherein the acknowledgement signal includes a first received signal strength indication (RSSI) value for the first measuring signal, and the first RSSI value is a function of the amplitude of the first measuring signal as received by the remote transmitter;

establishing at least one authorization zone based upon the geometrical shape of the signal radiated from the first antenna, wherein the authorization zone is established using at least one corresponding set of predetermined RSSI value ranges correlating to the first measuring signal; and

determining whether the remote transmitter is in the at least one authorization zone by comparing whether the first RSSI value is within at least one of the RSSI value ranges.

2. The method of claim 1, wherein the authorization zone further comprises, at least one inclusion area and at least one exclusion area, and the at least one inclusion and exclusion area being established using the RSSI of the first antenna.

3. The method of claim 2 further comprising:

determining if the remote transmitter is located within at least one exclusion area.

4. The method of claim 3 further comprising:

determining if the remote transmitter is located within at least one inclusion area.

5. the method of claim 4 further comprising:

determining if the remote transmitter should be granted access to a requested vehicle operation using an authentication security protocol, the authentication security protocol being performed when it is determined that the remote transmitter is located within at least one inclusion area; and

granting the remote transmitter access to the vehicle operation requested.

6. The method of claim 1 wherein the at least one measuring signal is transmitted using a low frequency (LF) signal.

7. The method of claim 1 wherein the acknowledgement signal is transmitted using an ultra high frequency (UHF) signal.

8. The method of claim 7 wherein the acknowledgement signal is transmitted using multiple UHF signals.

9. The method of claim 1 wherein at least one of the geometrical shapes is circular with a central location radiating from the first antenna.

10. The method of claim 1 further comprising:

transmitting at least one measuring signal from a first antenna located about the vehicle to a remote transmitter; and

the at least one of the geometrical shape is elliptical with a pair of focus points being defined using the first antenna and second antenna.

11. A method for determining the location of a remote transmitter positioned near a vehicle, the method comprising:

transmitting at least two measuring signals to a remote transmitter, the at least two measuring signals being transmitted from a first and second antenna positioned about the vehicle;

receiving an acknowledgement signal in response to the measuring signal from the remote transmitter, wherein the acknowledgement signal includes a received signal strength indication (RSSI) for each measuring signal received;

establishing an authorization zone using an elliptical shape, the elliptical shape being established using the first antenna to establish a first focus point and the second antenna to establish a second focus point, and the authorization zone having at least one inclusion area and at least one exclusion area;

determining a constant value using the sum of the distances from the first focus point and second focus point, wherein the constant value is used to define the curvature of the elliptical shape; and

determining the location of the remote transmitter by comparing whether the acknowledgment signal indicates that the remote transmitter is positioned within the at first authorization zone.

12. The method of claim 11, wherein the at least one inclusion and exclusion area are established using the RSSI from each measuring signal received, and determining that the remote transmitter is located within the at least one inclusion area when the sum of the RSSI from each measuring signal received is less than the constant value.

13. The method of claim 12 further comprising:

converting the RSSI from the first measuring signal to a first distance value, the first distance value being equal to the distance between the first antenna and the remote transmitter;

converting the RSSI from the second measuring signal to a second distance value, the second distance value being equal to the distance between the second antenna and the remote transmitter; and

determining that the remote transmitter is located within the inclusion area when the sum of the first and second distance values is less than the major diameter of the elliptical shape.

14. The method of claim 11 further comprising:

transmitting at least a third measuring signal to the remote transmitter using at least a third antenna;

establishing the authorization zone using the first, second, and third antennas to establish at least a first, second and third elliptical shape, and establishing the authorization zone using the first, second, and third antennas to establish at least a first second and third circular shape; and

determining the location of the remote transmitter by comparing whether the acknowledgment signal indicates that the remote transmitter is positioned within the authorization zone.

15. A system for determining the location of a remote transmitter positioned near a vehicle, the system comprising:

at least a first antenna located about the vehicle, the first antenna transmitting at least one measuring signal to a remote transmitter; and

a controller configured to;

receive an acknowledgement signal from the remote transmitter in response to the measuring signal, wherein the acknowledgement signal includes a received signal strength indication (RSSI) for each measuring signal received;

establish at least one authorization zone based upon the geometrical shape of the signal radiated from the first antenna, the at least one authorization zone being used to define a location relative to the vehicle; and

determine the location of the remote transmitter by verifying whether the acknowledgment signal indicates that the remote transmitter is positioned within the at least one authorization zone.

16. The system of claim 15, wherein the controller is further configured to establish at least one inclusion area and at least one exclusion area, and the at least one inclusion and exclusion area being established based upon the RSSI of the at least first antenna.

17. The system of claim 15, wherein the controller is further configured to:

determine if the remote transmitter is located within at least one exclusion area; and

deny the remote transmitter access to a particular vehicle operation when the remote transmitter is located within at least one exclusion area.

18. The system of claim 17, wherein the controller is further configured to:

determine if the remote transmitter is located within at least one inclusion area; and

grant the remote transmitter access to the particular vehicle operation when the remote transmitter is located within at least one inclusion area.

19. The system of claim 15 wherein the acknowledgement signal is a ultra high frequency (UHF) signal.

20. The system of claim 15 wherein the measuring signal is transmitted using a low frequency (LF) signal.