SYNCHRONIZATION OF A REAL-TIME UWB LOCATING SYSTEM

• US 20150200706A1
• Filed: 07/12/2012
• Published: 07/16/2015
• Est. Priority Date: 07/12/2012
• Status: Active Grant

• Current Assignee: Consorzio Nazionale Interuniversitario per le Telecomunicazioni (CNIT), Datalogic IP Tech S.r.l. (Datalogic S.p.A.), Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Datalogic IP Tech S.r.l. (Datalogic S.p.A.)
• Inventors: Bottazzi, Marco, Natali, Federico, Savioli, Enrico, Hadaschik, Niels, Dardari, Davide, Conti, Andrea
• Granted Patent: US 9,413,418 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 13/75 using transponders powered from received waves, e.g. using passive transponders , or using passive reflectors
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 7/40 Means for monitoring or calibrating
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7073 Synchronisation aspects
• CPC Class Codes: H04B 1/7183 Synchronisation

Abstract

In a UWB real time locating system, UWB readers (12) are synchronized by adjusting a clock of a UWB slave reader (12) until the UWB reader (12) receives each UWB pulse (34) of a sequence of UWB pulses (34) having a predetermined pulse period (Tp) and encoding a master UWB reader unique identifier at an expected time slot (35) within each predetermined pulse period (Tp), the expected time slot (35) being related to the distance between the UWB tag reader (12) and a master UWB reader (12).

Claims

1. A UWB tag reader (12) comprising:

a memory (513, 528) storing a quantity representative of the distance between the UWB tag reader and a master UWB reader, and a master UWB reader unique identifier,

a clock (503, 505) providing a reference clock signal (506) that drives the UWB communication activity, the activity being based on a periodic transmission of a plurality of UWB pulses (34) encoding an information, having a predetermined pulse period (Tp), and

a clock adjuster (505) that adjusts the reference clock signal (506) until the UWB reader (12) receives each UWB pulse (34) of a sequence of UWB pulses (34) having the predetermined pulse period (Tp) and encoding the master UWB reader unique identifier at an expected time slot (35) within each predetermined pulse period (Tp), the expected time slot (35) being related to the distance between the UWB tag reader (12) and a master UWB reader (12).

2. The UWB tag reader of claim 1, wherein the master UWB reader unique identifier is a spreading code uniquely associated with the master UWB reader (12).

3. The UWB tag reader of claim 1, wherein the master UWB reader unique identifier is embedded in an information packet transmitted by the master UWB reader (12).

4. The UWB tag reader of claim 2, wherein the clock (503, 505) provides a clock signal (506) on which a chip period (Tc) divided into time slots (Tf, 35) is based, and the clock adjuster (505) adjusts the clock signal (506) until the UWB reader (12) receives each UWB pulse (34) of a sequence of UWB pulses (34) having the predetermined pulse period (Tp) and encoding the master UWB reader spreading code at an expected time slot (35) within each of a plurality of chips (32).

5. The UWB tag reader of claim 2, wherein the clock adjuster (505) adjusts the clock signal (506) by shifting it by one time slot (Tf, 35) every information bit transmission (Nc*Np*Tp).

6. The UWB tag reader of claim 2, wherein the UWB pulses (34) having the predetermined pulse period (Tp) and encoding the master UWB reader spreading code comprise a plurality (Np) of successive equal pulses for each chip (32) of the master device spreading code.

7. The UWB tag reader of claim 1, comprising a receiving module configured to receive UWB pulses (34) having the predetermined pulse period (Tp) and to check whether they encode the master UWB reader unique identifier.

8. The UWB tag reader of claim 2, comprising a receiver module configured to monitor at least one time slot (35) each chip period (Tc) and to accumulate energy of UWB pulses (34) received in each of said at least one time slot (Tf) for each chip (32) of the master UWB reader spreading code.

9. The UWB tag reader of claim 1, comprising a tag interrogation module and the clock adjuster (505) is operated concurrently with or alternately with the tag interrogation module.

10. The UWB tag reader of claim 9, wherein the tag interrogation module comprises a transmitter (530) of UWB pulses (34) having the pulse period and encoding a UWB reader'"'"'s own unique identifier.

11. The UWB tag reader of claim 7, wherein the receiver module is further adapted to check whether the received UWB pulses (34) having the predetermined pulse period (Tp) encode the UWB reader'"'"'s own unique identifier and modulated with a unique identifier of a tag.

12. The UWB tag reader of claim 1, wherein the clock adjuster (505) comprises an input of a coarse synchronization signal (504).

13. A real-time UWB′

locating system (10) comprising at least one UWB reader (12) as claimed in claim 1 and at least one further UWB reader (12) comprising a transmitter (530) of UWB pulses (34) having the predetermined pulse period (Tp) and encoding the master UWB reader unique identifier.

14. The system (10) of claim 13, wherein the at least one further UWB reader (12) cyclically transmits a series of sequences of UWB pulses (34) having the predetermined pulse period (Tp) and encoding the master UWB reader unique identifier.

15. The system (10) of claim 13, further comprising at least one tag (14) comprising an antenna for backscattering UWB pulses (34), and a module configured to periodically set an antenna load according to a tag unique identifier, wherein the unique identifiers are spreading codes and a setting period corresponds to a chip period.

16. The system (10) of claim 15, wherein each tag (14) further comprises a module configured to periodically set an antenna load according to an information packet including a tag ID, a setting period corresponding to a symbol period (Ts) integer multiple of a chip period (Tc).

17. A UWB real-time locating system synchronization method comprising the steps of:

cyclically transmitting (202) from a master UWB reader (12) a sequence of UWB pulses (34) having a predetermined pulse period (Tp) and encoding a master UWB reader unique identifier,

receiving (203) at a slave UWB reader (12) UWB pulses (34),

providing at the slave UWB reader (12) a reference clock signal (506) that drives the UWB communication activity, the activity being based on a periodic transmission of a plurality of pulses (34) encoding an information, having a predetermined pulse period (Tp), and,

adjusting (217) the reference clock signal (506) at the slave UWB reader (12) until the slave UWB reader (12) receives each UWB pulse (34) of the sequence of UWB pulses (34) having the predetermined pulse period (Tp) and encoding the master UWB reader unique identifier at an expected time slot (35) within each predetermined pulse period (Tp), the expected time slot (35) being related to a distance between the slave UWB reader (12) and a master UWB reader (12).

18. The method of claim 17, wherein said unique identifiers are spreading codes and the step of adjusting (217) comprises shifting the clock signal (506) by a duration of one time slot (TO every information bit transmission (Nc*Np*Tp).

19. The method of claim 17, comprising a preliminary step (420) of communicating to the slave UWB reader (12) a coarse synchronization signal (504) using a communication channel (20) distinct from the UWB communication channel.

20. The method of claim 19, wherein the communication channel (20) uses a software-based synchronization protocol.

21. A method of operating a real-time UWB locating system (10) comprising a plurality of UWB readers (12) and a plurality of tags (14), comprising the steps of:

providing (410) to at least one UWB reader (12) of the system (14) a master UWB reader unique identifier (513) and a quantity (528) representative of the distance between the UWB reader (12) and a master UWB reader (12),

periodically transmitting (202) a tag interrogation signal from each UWB reader (12) of the system (10), the tag interrogation signal comprising a predetermined number of pulses (34) transmitted with a predetermined pulse period (Tp) and encoding a UWB reader'"'"'s unique code;

receiving at each UWB reader (12) a sequence of said predetermined number of UWB pulses (34) having the predetermined pulse period (Tp),

checking (207, 208, 216-218) whether the received sequence encodes a master reader unique identifier, and in the affirmative case adjusting (217) a clock signal (506) of the receiving UWB reader (12) so that the received sequence is received at an expected time slot (35) within each predetermined pulse period (Tp), the expected time slot (35) being related to a distance between the UWB reader (12) and a master UWB reader (12).

22. The method of claim 21, wherein said unique identifiers are spreading codes and said step of periodically transmitting (202) comprises periodically transmitting a tag interrogation packet from each UWB reader (12) of the system (10), the tag interrogation packet comprising a plurality of information bits (30, 31) transmitted with an information bit period (Ts), each information bit (30, 31) being modulated by a UWB reader'"'"'s own spreading code into a plurality of chips (32) transmitted with a chip period (Tc), each chip (32) being modulated into a predetermined number (Np) of pulses (34) transmitted with a pulse period (Tp);

and said step of checking (207, 208, 216-218) comprises checking whether the received sequence encodes a master UWB reader spreading code, and in the affirmative case adjusting a clock signal (506) of the receiving UWB reader (12) so that the received sequence is received at an expected time slot (35) within each chip (32), the expected time slot (35) being related to a distance between the UWB reader (12) and a master UWB reader (12).

23. The method of claim 21, further comprising checking (209-212, 219-222) whether the received sequence encodes the UWB reader'"'"'s own unique identifier and in the affirmative case computing (221, 222, 227) a distance (22-24) from an item (14) based on the time slot (35) in which the sequence has been received.

24. The method of claim 21, further comprising receiving a plurality of UWB pulse sequences encoding the UWB reader'"'"'s own unique identifier and checking (227) whether the plurality of UWB pulse sequences further encodes a tag unique identifier and/or a tag ID.