EXTENSIBLE OBJECT LOCATION SYSTEM AND METHOD USING MULTIPLE REFERENCES

• US 20120188129A1
• Filed: 03/30/2012
• Published: 07/26/2012
• Est. Priority Date: 05/10/2005
• Status: Active Grant

• Current Assignee: Zebra Technologies Corporation
• Original Assignee: Multispectral Solutions Incorporated (Zebra Technologies Corporation)
• Inventors: Ameti, Aitan, Chen, Keming, Fontana, Robert J., Richley, Edward A., Turner, Belinda
• Granted Patent: US 9,360,547 B2
• Time in Patent Office: Days
• US Class Current: 342/451
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/02213 Receivers arranged in a network for determining the position of a transmitter
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308

Abstract

An ultra wideband (UWB) or short-pulse RF system is disclosed that can be used to precisely locate or track objects (such as personnel, equipment, assets, etc.) in real-time in an arbitrarily large, physically connected or disconnected, multipath and/or noisy environment. A system implementation includes multiple zones or groups of receivers that receives RF signals transmitted by one or more timing reference tags and one or more objects having associated object tags. Each zone or group may share a common receiver. By combining a multiple reference tag system with a virtual group of receivers, i.e., a zoning technique or system, a cost-effective system can be provided that offers scalability and flexibility to monitor a significantly expanded coverage area.

Claims

1. A zone-based object location system to determine a position of an object in one of multiple zones, the object being associated with an object tag that transmits an RF object signal, the system comprising:

respective groups of receivers, each group of receivers including multiple receivers and defining a corresponding zone, wherein at least one receiver is common to at least two zones and wherein each receiver includes a timing circuit to detect an arrival time of an RF signal;

a clock source to lock phase relations of the timing circuits relative to each other;

a reference tag associated with each zone is configured to transmit an RF reference signal from a known location within the zone; and

a processing hub configured to obtain time-of-arrival information indicative of arrival times of the RF object signal transmitted by the object tag and the RF reference signal transmitted by the reference tag at receivers of a group of receivers to determine the position of the object within one of the multiple zones.

2. The zone-based object location system of claim 1, wherein the timing circuit comprises a free-running digital counter.

3. The zone-based object location system of claim 1, wherein the clock source is common to the multiple zones and supplies a clock signal to the groups of receivers via a daisy-chained wireline data cable.

4. The zone-based object location system of claim 3, wherein the processing hub obtains digital representations of the time-of-arrival information from the timing circuits of the receivers via the wireline data cable.

5. The zone-based object location system of claim 1, wherein the processing hub is configured to obtain time-of-arrival information indicative of arrival times of the RF object signal transmitted by the object tag and RF reference signals transmitted by two reference tags and wherein the respective zones associated with the two reference tags overlap.

6. The zone-based object location system of claim 1, wherein the processing hub is configured to determine the position of the object by the relative phase relations of the timing circuits.

7. The zone-based object location system of claim 1, wherein the reference tag is configured to transmit an ID code to distinguish among multiple ones of the reference tags when determining the position of the object by time differences of arrival.

8. The zone-based object location system of claim 1, wherein each zone is defined by a RF signal transmission range.

9. A zone-based object location system to determine a position of an object in one of multiple zones of a region, each object being associated with an object tag, the system comprising:

respective groups of receivers, each group of receivers configured to include multiple receivers and define a corresponding zone, wherein at least one receiver is common to at least two zones and wherein each receiver includes a free-running digital counter to measure an arrival time of an ultra-wideband signal;

a clock common to the multiple zones configured to lock the free-running digital counters in relative phase relationship via a daisy-chained cable;

a reference tag associated with each zone is configured to transmit an ultra-wideband signal from a known location within the zone to provide a timing reference; and

a processing hub configured to obtain digital representations of time-of-arrival information indicative of the timing reference and arrival times of the ultra-wideband signal transmitted by the reference tag at receivers of a group of receivers to determine the position of the object.

10. The zone-based object location system of claim 9, wherein the free-running digital counters are synchronized in frequency, but not necessarily in phase, by the clock.

11. The zone-based object location system of claim 9, wherein the processing hub is configured to determine the position of the object by the relative phase relations locked by the free-running digital counters.

12. The zone-based object location system of claim 9, wherein the processing hub is configured to obtain time-of-arrival information indicative of arrival times of the RF object signal transmitted by the object tag and RF reference signals transmitted by two reference tags.

13. The zone-based object location system of claim 12, wherein the respective zones of the two reference tags overlap.

14. The zone-based object location system of claim 12, wherein the respective zones of the two reference tags are separated by a distance.

15. The zone-based object location system of claim 12, wherein the respective zones of the two reference tags are adjacent.

16. A zone-based object location method to determine a position of an object in a region, the method comprising:

defining zones by respective groups of receiver in a monitored region in which to detect the object, wherein at least one receiver is common to at least two zones;

receiving an RF reference signal transmitted from a reference tag at two or more receivers from a known location within a zone;

receiving an RF object signal transmitted from an object tag associated with the object at the two or more receivers within the zone;

recording, by timing circuits, arrival times of the received RF reference signal and the received RF object signal at the two or more receivers; and

acquiring, by a processing hub, time-of-arrival information indicative of the arrival times to determine the position of the object in one of the zones within the region.

17. The method of claim 16, further comprising supplying a clock signal to the groups of receivers by a clock source common to the zones within the region.

18. The method of claim 16, further comprising determining phase relations of the timing circuits relative to each other to determine the position of the object.

19. The method of claim 16, further comprising arranging the groups of receivers in a pattern to define a matrix of rows and columns of zones.

20. The method of claim 16, further comprising determining timing offsets of the two or more receivers, determining the differences in time of arrival of the RF object tag signal and determining the position of the object.