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Passive entry system and method for a vehicle

  • US 8,284,020 B2
  • Filed: 12/22/2009
  • Issued: 10/09/2012
  • Est. Priority Date: 12/22/2009
  • Status: Active Grant
First Claim
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1. 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, wherein the at least one inclusion and exclusion area are established using the RSSI from each measuring signal received;

    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;

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

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