Method and system of locating objects

• US 8,624,774 B2
• Filed: 03/17/2011
• Issued: 01/07/2014
• 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
• Primary Examiner(s): Keith, Jack W
• Assistant Examiner(s): BYTHROW, PETER M
• Application Number:
  US13/050,626
• Publication Number:
  US 20110228820A1
• Time in Patent Office: 1,027 Days
• Field of Search: 342/27, 342/42, 342/44, 342/51, 342/118, 342/126, 342/127, 342/146, 342/147, 342/175, 342/378, 342/450, 342/451, 342/458, 342/461, 342/463, 342/464, 342/465, 340/539.1, 340/539.11, 340/539.13, 340/539.14, 340/539.15, 340/568.1, 340/573.1, 340/686.6, 368/10, 368/11, 368/14, 368/238, 368/327
• US Class Current: 342/42
• 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 synchronized. 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, wherein the search device includes a transceiver associated with a pair of antennae that are spaced apart from each other, a display means, and an electronic means for managing the transceiver and the display means, wherein the target device includes a transceiver associated with an antenna and with an electronic means capable of detecting the reception of signals originating from the search device,

wherein the signals are UWB signals, and wherein the method includes

a locating phase including at least one locating sequence, wherein the locating sequence includes the steps of

a) emitting two respective locating signals across the two antennae of the search device, wherein he search device emits the two locating signal;

b) measuring a time difference between reception of the two locating signals, wherein the target device receives the two locating signals and measures a time difference between reception of the two signals;

c) encoding and emitting a return signal containing an indication relating to the time difference, wherein the target device encodes and emits the return signal;

d) receiving and decoding the return signal at least across one of the two antennae of the search device, wherein the search device receives and decodes the return signal;

e) measuring at least a total time between the emission of one of the two locating signals and reception of the return signal by one of the two antennae of the search device and calculating both travel times, of the two locating signals, between, respectively, the two antennae of the search device and the antenna of the target device on the basis of the total time, the time difference, and a processing time between one or the other reception of the two locating signals by the target device and the emission of the return signal by the target device;

f) calculating at least a direction or two possible directions of the object by triangulation, based on the two travel times and the space between the two antennae of the search device; and

g) displaying at least the direction or the two possible directions of the object.

2. The method according to claim 1, wherein a 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 the target device in the return signal, wherein the search device is disposed to decode the duration of processing.

3. The method according to claim 2, wherein the at least one 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 at least one locating sequence and the change in the display is observed after the repetition.

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

6. The method according to claim 4, wherein, in the search device the coordinates of the possible positions supplied by a first locating sequence are stored, the movements of the search device are measured, the coordinates of the possible positions and the display of the possible positions are updated according to the 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 the possible positions.

7. The method according to claim 1, wherein the method includes a wake up phase prior to the locating phase, and wherein the wake up phase includes the steps of:

a) activating the target device by means of a wake up signal containing an identity code of the target device, wherein the search device sends the wake up signal; and

b) responding to the wake up signal with an acknowledgement of receipt signal, wherein the target device responds to the wake up signal.

8. The method according to claim 2, wherein the method includes a wake up phase prior to the locating phase, and wherein the wake up phase includes the steps of:

a) activating the target device by means of a wake up signal containing an identity code of the target device, wherein the search device sends the wake up signal; and

b) responding to the wake up signal with an acknowledgement of receipt signal, wherein the target device responds to the wake up signal.

9. The method according to claim 1, wherein the duration of processing between the first reception or the second reception of the locating signal and the emission of the return signal is a predetermined value.

10. The method according to claim 1, wherein the two locating signals are emitted simultaneously.