Method of determining vehicle location from key fob

• US 8,547,253 B2
• Filed: 09/04/2009
• Issued: 10/01/2013
• Est. Priority Date: 09/04/2009
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: Proefke, David T., McCall, Clark E., Biondo, William A., Lust, Robert V.
• Primary Examiner(s): Lu, Shirley
• Application Number:
  US12/554,150
• Publication Number:
  US 20110057817A1
• Time in Patent Office: 1,488 Days
• Field of Search: 340/989, 340/5.72, 340/457
• US Class Current: 340/989
• CPC Class Codes: G01S 13/74 Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
• CPC Class Codes: H01Q 1/3241 particular used in keyless entry systems

Abstract

A method of indicating a proximity value representative of the distance between a key fob (202) and a vehicle (102) includes transmitting (304, 406, 504) at least one locate signal from the key fob (202) to the vehicle (102), transmitting (364, 468, 562) at least one response signal from the vehicle (102) to the key fob (202) in response to the at least one locate signal, performing (362, 462, 510) RSSI measurements of either the at least one locate signal or the at least one response signal, and displaying (318, 412, 514) the proximity value on the key fob (202) based on the RSSI measurements.

Claims

1. A method of indicating a proximity value representative of the distance between a key fob system and a vehicle system, comprising:

transmitting an N plurality of locate signals from the key fob, each of the N plurality of locate signals having a different signal strength;

performing RSSI measurements for the N plurality of locate signals received by the vehicle system;

determining a proximity value by the vehicle system based on the N plurality of locate signals received;

determining by the vehicle system the power level optimal for distinguishing proximity using the signal strength of the N received locate signals;

transmitting from the vehicle system the transmit power level for the next key fob transmission along with the RSSI value and the proximity value;

displaying a proximity value on the key based on RSSI measurements;

setting the key fob system transmission power signal strengths of an N+1 plurality of locate signals to that received from the vehicle system and a level greater than that received from the vehicle system; and

transmitting the N+1 plurality of locate signals from the key fob system, each of the N+1 plurality of locate signals having a different signal strength.

2. The method of claim 1 further comprising repeating each of the steps in succession a plurality of times.

3. The method of claim 1 further comprising calculating the proximity value based on at least one of the RSSI values within a preferred range of RSSI values.

4. The method of claim 3 further comprising repeating each of the steps a plurality of times in succession.

5. The method of claim 4 wherein the performing step comprises rejecting RSSI measurements that exceed a maximum rate of change.

6. An apparatus for indicating a proximity value representative of the distance between a key fob system and a vehicle system, comprising:

the key fob system configured for transmitting an N plurality of locate signals to the vehicle system, each of the N plurality of locate signals having a different signal strength

the vehicle system configured to;

perform RSSI measurements of the N plurality of locate signals received by the vehicle system;

determine a proximity value based on the N plurality of locate signals received;

determine the power level optimal for distinguishing proximity using the signal strength of the N received locate signals;

transmit the transmit power level for the next key fob transmission along with the RSSI value and the proximity value; and

a display on the key fob configured for displaying the proximity value based on RSSI measurements;

wherein the key fob system is further configured to;

set the key fob system transmission power signal strengths of an N+1 plurality of locate signals to that received from the vehicle system and a level greater than that received from the vehicle system; and

transmitting the N+1 plurality of locate signals from the key fob system, each of the N+1 plurality of locate signals having a different signal strength.