METHOD AND SYSTEM OF LOCATING OBJECTS

• US 20110228820A1
• Filed: 03/17/2011
• Published: 09/22/2011
• Est. Priority Date: 03/17/2010
• Status: Active Grant

• Current Assignee: The Swatch Group Research And Development Ltd
• Original Assignee: The Swatch Group Research And Development Ltd
• Inventors: De Rosa, Luca
• Granted Patent: US 8,624,774 B2
• Time in Patent Office: Days
• US Class Current: 375/147
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 13/765 with exchange of information between interrogator and responder

Abstract

The invention concerns a method and system of locating objects by means of UWB signals, the system including a search device (D1), incorporated in a portable apparatus (11) and provided with a pair of antennae (A1, A2), and at least one target device (D2) attached to an object sought (12). The target device (D2) includes, in addition to the transceiver (34, 35), a very low power consumption wake up receiver (46) which, when the target device is in a standby state, can receive a UWB wake up signal to switch on said device. This target device is arranged for measuring a time difference (tdiff) between the respective receptions of two locating signals respectively emitted by the two antennae (A1, A2) of the search device and for transmitting said time difference in a return signal that further contains, in a preferred variant, a signal processing time (trproc). Thus, it is not necessary for the two devices to be synchronised. Preferably, the search device (D1) is incorporated in a wristwatch (11) the two hands (51, 52) of which are used for indicating the direction or possible directions of the object sought (12).

Claims

1. A method of locating an object sought, by means of electromagnetic signals exchanged between a search device incorporated in a portable apparatus, and a target device attached to the object sought, wherein the search device includes a transceiver, associated with a pair of antennae spaced apart from each other, display means and electronic means for managing the transceiver and the display means, and wherein the target device includes a transceiver associated with an antenna and with electronic means capable of detecting the reception of signals originating from the search device;

wherein said signals are UWB signals and wherein the method includes the following successive phases;

a wake up phase in which the target device is activated by the search device by means of a wake up signal containing an identity code for the target device and responds with an acknowledgement of receipt signal, and

a locating phase including at least one locating sequence in which;

a) the search device emits two respective locating signals across the two antennae thereof;

b) the target device receiving the two locating signals measures a difference between the respective travel times of said two locating signals between the two antennae of the search device and the antenna of said target device;

c) the target device elaborates and emits a return signal containing an indication relating to said travel time difference;

d) the search device measures a total time between the emission of at least one of the two locating signals and the first reception or the second reception of the return signal by one of the two antennae thereof and calculates said travel times on the basis of said total time, said difference between the travel times and a processing time between the first reception or the second reception of the locating signal and the emission of the return signal; and

e) the search device calculates the position or the two possible positions of the object sought by triangulation, based on said travel times and the space between the two antennae thereof, and displays at least the direction of said position or said possible positions.

2. The method according to claim 1, wherein said duration of processing between the first reception or the second reception of the locating signal and the emission of the return signal is determined by the target device and transmitted by send target device in said return signal.

3. The method according to claim 2, wherein the locating sequence is repeated periodically or on request.

4. The method according to claim 3, wherein a movement is imparted to the search device before a repetition of the locating sequence and the change in the display is observed after said repetition.

5. The method according to claim 4, wherein said movement is a rotation of the search device on itself or a translation in the direction of one of said possible positions.

6. The method according to claim 4, wherein, in the search device the coordinates of said possible positions supplied by a first locating sequence are stored, the movements of the search device are measured, the coordinates of said possible positions and the display thereof are updated according to said movements, and wherein the possible positions calculated in a second locating sequence are compared to those of the first locating sequence in order to make a choice between said possible positions.

7. The object location system for implementing the method according to claim 1, including a search device incorporated in a portable apparatus, and a target device attached to the object sought, wherein the search device includes a transceiver, associated with a pair of antennae spaced apart from each other, display means for indicating at least one direction and electronic means for managing the transceiver and the display means, and wherein the target device includes a transceiver associated with an antenna and with electronic means capable of detecting the reception of signals originating from the search device and responding thereto;

wherein the signals exchanged between the search device and the target device are UWB signals; and

wherein the target device further includes a wake up receiver arranged for receiving and decoding a wake up signal when the target device is in a standby state and, when the wake up signal contains an identity code for the target device, switching on said transceiver.

8. The system according to claim 7, wherein the target device is arranged for measuring a time difference between the respective receptions of two locating signals respectively emitted by the two antennae of the search device and for incorporating a representation of said time difference in a return signal.

9. The system according to claim 8, wherein said target device is also arranged for determining a processing time between the reception of the first or second of the two locating signals and the emission of said return signal.

10. The system according to claim 7, wherein said portable apparatus is an electronic watch having an analogue time display the two hands of which are used by the search device for simultaneously indicating two possible directions or a single determined direction by the superposition of said hands.

11. The system according to claim 10, wherein the watch includes a digital display used by the search device for indicating a distance between the search device and the target device.

12. A search device, notably for implementing the object location method according to claim 1, including a transceiver associated with a pair of antennae spaced apart from each other, display means for indicating at least one direction and electronic means for managing the transceiver and the display means;

wherein the transceiver is a UWB transceiver and wherein the display means thereof includes two hands capable of simultaneously indicating two possible directions or a single determined direction by superposition of said hands.

13. The search device according to claim 12, wherein it is incorporated in an electronic watch having an analogue time display.

14. The search device according to claim 13, wherein the watch includes a digital display able to provide a time indication and used by the search device to indicate a distance between said search device and a target device.

15. A target device, notably for implementing the object location method according to claim 1, including a transceiver associated with an antenna and with electronic means capable of detecting reception of signals originating from the associated search device;

wherein the transceiver is a UWB type transceiver;

wherein the target device includes a circuit for measuring a difference in reception time between two locating signals received at different times; and

wherein it includes means for elaborating and emitting a return signal containing an indication relating to said difference in reception time.

16. The target device according to claim 15, wherein it includes means for determining a processing time between the reception of one of the two locating signals and the emission of said return signal, and wherein it is arranged for transmitting an indication relating to said processing time in said return signal.

17. The target device according to claim 15, wherein it further includes a wake up receiver arranged for receiving and decoding a wake up signal when said device is in a standby state and, when the wake up signal contains an identity code for said target device, for switching on said transceiver.

18. The target device according to claim 16, wherein it further includes a wake up receiver arranged for receiving and decoding a wake up signal when said device is in a standby state and, when the wake up signal contains an identity code for said target device, for switching on said transceiver.