RADIO FREQUENCY TAG LOCATION SYSTEM AND METHOD

• US 20120276921A1
• Filed: 03/14/2012
• Published: 11/01/2012
• Est. Priority Date: 04/26/2011
• Status: Active Grant

• Current Assignee: Microchip Technology Incorporated
• Original Assignee: Microchip Technology Incorporated
• Inventors: Németh, József G.
• Granted Patent: US 8,688,140 B2
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: G01S 1/30 the synchronised signals being continuous waves or intermittent trains of continuous waves, the intermittency not being for the purpose of determining direction or position line and the transit times being compared by measuring the phase difference
• CPC Class Codes: G01S 3/043 Receivers
• CPC Class Codes: G01S 3/48 the waves arriving at the antennas being continuous or intermittent and the phase difference of signals derived therefrom being measured
• CPC Class Codes: G01S 5/04 Position of source determined by a plurality of spaced direction-finders
• 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

Determination of the location and bearing of an asset having an RF-tag imbedded therein is accomplished through extended radio frequency triangulation. A beacon arrangement determines the direction of an RF tag from a specially designed beacon node. RF-tag localization is further improved by repeating this measurement from multiple spatially displaced beacon nodes. The beacon nodes are equipped with multiple strategically located antennas and transmit frames with each symbol cyclically switched to a different antenna. The symbols traveling different distances result in phase shifts within the frame received by the RF-tag. From the phase shifts and the known arrangements of the antennas the angle at which the RF-tag is RF visible from the specific beacon node can be estimated. Determination of the signal phase shifts are part of the baseband processing hardware, the rest of the location determination procedure may be realized in software.

Claims

1. A method for locating a radio frequency tag using spatially separated beacon nodes, said method comprising the steps of:

transmitting a plurality of beacon symbols from cyclically selected antennas of each of a plurality of beacon nodes;

receiving the plurality of beacon symbols at a radio frequency (RF) tag;

determining phase jumps of the plurality of beacon symbols received at the RF tag and the respective selected antennas transmitting each of the plurality of beacon symbols for each of the plurality of beacon nodes;

estimating an angle-of-arrival (AoA) of the plurality of beacon symbols transmitted from each of the plurality of beacon nodes;

estimating an AoA vector for each of the plurality of beacon nodes from the respective AoA estimates; and

estimating a spatial location of the RF tag from the AoA vectors.

2. The method according to claim 1, wherein each next one of the plurality of beacon symbols is transmitted from a next one of the cyclically selected antennas.

3. The method according to claim 1, wherein every other next one of the plurality of beacon symbols is transmitted from a next one of the cyclically selected antennas.

4. The method according to claim 1, wherein the plurality of beacon symbols are payload portions of IEEE 802.15.4 standard compliant frames.

5. The method according to claim 1, wherein the step of estimating the AoA of the plurality of beacon symbols transmitted from each of the plurality of beacon nodes comprises the step of determining the phase jump of each one of the plurality of beacon symbols in relation to a respective one of the cyclically selected antennas transmitting the one of the plurality of beacon symbols.

6. The method according to claim 1, wherein the step of estimating the AoA of the plurality of beacon symbols transmitted from each of the plurality of beacon nodes comprises the step of determining the phase jump of every other one of the plurality of beacon symbols in relation to a respective one of the cyclically selected antennas transmitting the every other one of the plurality of beacon symbols.

7. The method according to claim 1, wherein the step of estimating the AoA provides an azimuth angle estimation.

8. The method according to claim 1, wherein the step of estimating the AoA provides an elevation angle estimation.

9. The method according to claim 1, further comprising the steps of calibrating position and orientation of each one of the plurality of beacon nodes by

transmitting a plurality of beacon symbols from the cyclically selected antennas of a one of the plurality of beacon nodes;

and

receiving the plurality of beacon symbols on another one of the plurality of beacon nodes with a one of the antennas of the another one of the plurality of beacon nodes.

10. The method according to claim 1, further comprising the steps of calibrating position and orientation of each one of the plurality of beacon nodes by

transmitting a plurality of beacon symbols from a one of the antennas of a one of the plurality of beacon nodes;

and

receiving the plurality of beacon symbols on another one of the plurality of beacon nodes with the cyclically selected antennas of the another one of the plurality of beacon nodes.

11. The method according to claim 1, further comprising the steps of:

providing a central processing node; and

providing a network for coupled the central processing node to the plurality of beacon nodes.

12. The method according to claim 1, wherein each of the plurality of beacon nodes comprises:

a radio frequency (RF) device;

an antenna switch coupled between the RF device and the cyclically selected antennas; and

a digital processor having outputs that control the antenna switch and a trigger input coupled to the RF device, wherein when a switch antenna signal is received from the RF device the digital processor causes the antenna switch to coupled the RF device to a different one of the antenna.

13. The method according to claim 12, wherein the digital processor is a microcontroller.

14. The method according to claim 12, wherein the digital processor is selected from the group consisting of a microprocessor, a digital signal processor (DSP), a programmable logic array (PLA) and an application specific integrated circuit (ASIC).

15. A method for locating a radio frequency tag using spatially separated beacon nodes, said method comprising the steps of:

transmitting a plurality of beacon symbols from an antenna of a radio frequency (RF) tag;

receiving the plurality of beacon symbols on cyclically selected antennas of each of a plurality of beacon nodes;

determining phase jumps of the plurality of beacon symbols transmitted from the RF tag and the respective selected antennas receiving each of the plurality of beacon symbols for each of the plurality of beacon nodes;

estimating an angle-of-arrival (AoA) of the plurality of beacon symbols received at each of the plurality of beacon nodes;

estimating AoA vectors of each of the plurality of beacon nodes from the AoA estimates; and

estimating a spatial location of the RF tag from the AoA vectors.

16. The method according to claim 15, wherein each next one of the plurality of beacon symbols is received at a next one of the cyclically selected antennas.

17. The method according to claim 15, wherein every other next one of the plurality of beacon symbols is received at a next one of the cyclically selected antennas.

18. The method according to claim 15, wherein the plurality of beacon symbols are payload portions of IEEE 802.15.4 standard compliant frames.

19. The method according to claim 15, wherein the step of estimating the AoA of the plurality of beacon symbols received at each of the plurality of beacon nodes comprises the step of determining the phase jump of each one of the plurality of beacon symbols in relation to a respective one of the cyclically selected antennas receiving the one of the plurality of beacon symbols from the RF tag.

20. The method according to claim 15, wherein the step of estimating the AoA of the plurality of beacon symbols received at each of the plurality of beacon nodes comprises the step of determining the phase jump of every other one of the plurality of beacon symbols in relation to a respective one of the cyclically selected antennas receiving the every other one of the plurality of beacon symbols from the RF tag.

21. The method according to claim 15, wherein the step of estimating the AoA provides an azimuth angle estimation.

22. The method according to claim 15, wherein the step of estimating the AoA provides an elevation angle estimation.

23. The method according to claim 15, further comprising the steps of calibrating position and orientation of each of the plurality of beacon nodes by

transmitting a plurality of beacon symbols from the cyclically selected antennas of a one of the plurality of beacon nodes;

and

receiving the plurality of beacon symbols on another one of the plurality of beacon nodes with a one of the antennas of the another one of the plurality of beacon nodes.

24. The method according to claim 15, further comprising the steps of calibrating position and orientation of each one of the plurality of beacon nodes by

transmitting a plurality of beacon symbols from a one of the antennas of a one of the plurality of beacon nodes;

and

receiving the plurality of beacon symbols on another one of the plurality of beacon nodes with the cyclically selected antennas of the another one of the plurality of beacon nodes.

25. The method according to claim 15, further comprising the steps of:

providing a central processing node; and

providing a network for coupled the central processing node to the plurality of beacon nodes.

26. The method according to claim 15, wherein each of the plurality of beacon nodes comprises:

a radio frequency (RF) device;

an antenna switch coupled between the RF device and the cyclically selected antennas; and

a digital processor having outputs that control the antenna switch and a trigger input coupled to the RF device, wherein when a switch antenna signal is received from the RF device the digital processor causes the antenna switch to coupled the RF device to a different one of the antenna.

27. The method according to claim 26, wherein the digital processor is a microcontroller.

28. The method according to claim 26, wherein the digital processor is selected from the group consisting of a microprocessor, a digital signal processor (DSP), a programmable logic array (PLA) and an application specific integrated circuit (ASIC).