Method using ultra high frequency waves for locating a portable device giving “hands free” access to a vehicle, associated locating device and portable device

1. A method for locating a portable device (P′) for “hands free” access to a vehicle (V′) via a location device (D′) that is installed in the vehicle (V′), comprising:

communicating between the portable device (P′) and the location device (D′) by transmitting and receiving ultra high frequency signals as ultra high frequency waves, and simultaneously with every transmitting of an ultra high frequency signal by the location device (D′) to the portable device (P′), transmitting by the location device (D′) one of three successive ultrasonic signals originating respectively from three separate ultrasound sources, each ultra high frequency signal being transmitted simultaneously with an ultrasonic signal of a different one of the three ultrasound sources;

receiving, at the portable device (P′), the ultra high frequency signals and ultrasonic signals transmitted by the location device (D′);

measuring, at the portable device (P′) and for each ultra high frequency signal received at the portable device (P′), a time delay (Δt) between a first time of reception (t 1 ) of the received ultra high frequency signal and a second time of reception (t 2 ) of a corresponding ultrasonic signal received after reception of said received ultra high frequency signal; and

determining a position of the portable device (P′) with respect to the location device (D′) on the basis of the measured time delay (Δt).

2. A location device (D′), to be installed in a vehicle (V′), for determining a location of a portable device (P′) for “hands free” access to the vehicle (V′), the portable device (P′) configured to communicate with the location device (D′) by ultra high frequency waves, the location device (D′) comprising:

means of sequentially transmitting, simultaneously with each one of three ultra high frequency signals, one of three successive ultrasonic signals to the portable device (P′);

means of reception (M 2 ) of a delay (Δt) between a first time of reception (t 1 ) of each ultra high frequency signal received by the portable device (P′) and a second time of reception (t 2 ) of each ultrasonic signal received by the portable device (P′); and

means of computation (M 1 ) of a distance (d) between the portable device (P′) and the location device (D′) on the basis of the delay (Δt) thus received.

3. A portable device (P′) for “hands free” access to a vehicle, configured to operate with a location device (D′), the portable device (P′) comprising:

means for communicating with the location device (D′) by ultra high frequency waves;

means of reception (M 6 ) of three successive ultrasonic signals;

means of measuring (M 4 ) a delay (Δt) between a first time of reception (t 1 ) of an ultra high frequency signal and a second time of reception (t 2 ) of each ultrasonic signal received at the portable device (P′); and

means of transmission (M 5 ) of the delay (Δt) thus measured to the location device (D′).

4. A location device (D′), to be installed in a vehicle (V′), for locating a portable device (P′) for “hands free” access to the vehicle (V′), the portable device (P′) configured to communicate with the location device (D′) by ultra high frequency waves, the location device (D′) comprising:

means of sequentially transmitting, simultaneously with each one of three ultra high frequency signals, one of three successive ultrasonic signals to the portable device; and

means of reception of a distance (d) between the portable device (P′) and the location device (D′), coming from the portable device (P′).

5. A portable device (P′) for “hands free” access to a vehicle, configured for operation with a location device (D′), the said portable device (P′) comprising:

means for communicating with the location device (D′) by ultra high frequency waves

means of reception (M 6 ) of three successive ultrasonic signals;

means of measuring (M 4 ) a delay (Δt) between a first time of reception (t 1 ) of an ultra high frequency signal and a second time of reception (t 2 ) of each ultrasonic signal received by the portable device (P′);

means of computation of a distance (d) between the portable device (P′) and the location device (D′) on the basis of the delay (Δt) thus computed; and

means of transmission (M 5 ) of the said distance (d) to the location device (D′).

6. “Hands free” access system ( 100 ) comprising a location device (D′) according to claim 2 and a portable device (P′) for “hands free” access to a vehicle, intended to be located by a location device (D′), the portable device (P′) communicating with the location device (D′) by ultra high frequency waves, the portable device (P′) comprising:

means of reception (M 6 ) of three ultrasonic signals;

means of measuring (M 4 ) a delay (Δt) between a first time of reception (t 1 ) of each ultra high frequency signal and a second time of reception (t 2 ) of each ultrasonic signal; and

means of transmission (M 5 ) of the delay (Δt) thus measured to the location device (D′).

7. “Hands free” access system comprising a location device (D′) according to claim 4 and a portable device (P′) giving “hands free” access to a vehicle, intended to be located by a location device (D′), the said portable device (P′) communicating with the said location device (D′) by ultra high frequency waves, the portable device (P′) comprising:

means of reception (M 6 ) of three ultrasonic signals;

means of measuring (M 4 ) a delay (Δt) between a first time of reception (t 1 ) of each ultra high frequency signal and a second time of reception (t 2 ) of each ultrasonic signal by the portable device (P′);

means of computation of a distance (d) between the portable device (P′) and the location device (D′) on the basis of the delay (Δt) thus computed; and

means of transmission (M 5 ) of the said distance (d) to the location device (D′).

8. A motor vehicle (V′) comprising a location device (D′) according to claim 2 .

9. A motor H t r vehicle (V′) comprising a location device (D′) according to claim 4 .