MITIGATION OF MULTIPATH DISTORTIONS FOR TDOA-BASED GEOLOCATION

• US 20160370453A1
• Filed: 06/30/2014
• Published: 12/22/2016
• Est. Priority Date: 07/01/2013
• Status: Active Grant

• Current Assignee: Elbit Systems Bmd And Land Ew-Elisra Ltd. (Elbit Systems Limited)
• Original Assignee: Elbit Systems Bmd And Land Ew-Elisra Ltd. (Elbit Systems Limited)
• Inventors: Boker, Eyal, Levy, Avinoam, Goldreich, Rami
• Granted Patent: US 9,841,489 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/02213 Receivers arranged in a network for determining the position of a transmitter
• CPC Class Codes: G01S 5/0273 using multipath or indirect path propagation signals in position determination
• 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

Abstract

Method and system for radiolocation of RF transmitter in the presence of multipath interference. RF receivers are spatially separated at known locations in a moderate multipath environment in the vicinity of the transmitter. Upon detection of a received active RF signal associated with the transmitter, the receivers are directed to acquire measurements of the detected RF signal. Each receiver obtains a sequence of measurements of the RF signal at different positions along a trajectory that provides multiple measurements at relative phase differences between the direct-path and the multipath reflections of the detected RF signal. The receivers may be repositioned automatically or manually, or prearranged or selectively deployed at fixed positions along the trajectory. TDOA measurements between pairs of receivers are calculated based on the obtained measurements, and are averaged to provide a respective updated TDOA measurement value for each receiver pair, which is used to determine the transmitter location.

Claims

1. A method for determining a location of a radio frequency (RF) transmitter in the presence of multipath interference, the method comprising the procedures of:

providing a plurality of spatially separated RF receivers at known locations in a moderate multipath environment in the vicinity of said transmitter;

detecting an active RF signal associated with said transmitter received by at least one of said receivers, and directing said receivers to acquire measurements of the detected RF signal;

obtaining a sequence of measurements of said RF signal at different positions along a trajectory by each of said receivers, wherein said trajectory provides a plurality of measurements at relative phase differences between the direct-path and the multipath reflections of said detected RF signal;

calculating time difference of arrival (TDOA) measurements between pairs of said receivers based on the obtained measurements;

averaging the TDOA measurements for each of said pairs of receivers to provide a respective updated TDOA measurement value;

determining a location of said transmitter based on the updated TDOA measurement values.

2. The method of claim 1, wherein said trajectory comprises a circular trajectory.

3. The method of claim 1, wherein the range of said trajectory is at least half the wavelength of said detected RF signal.

4. The method of claim 1, wherein said procedure of obtaining a sequence of measurements of said RF signal at different positions along a trajectory by each of said receivers comprises repeatedly repositioning the receiver multiple times over a selected trajectory pattern.

5. The method of claim 1, wherein said procedure of obtaining a sequence of measurements of said RF signal at different positions along a trajectory by each of said receivers comprises arranging or selectively deploying a plurality of receivers at fixed positions along said trajectory.

6. The method of claim 1, wherein said procedure of obtaining a sequence of measurements of said RF signal at different positions along a trajectory by each of said receivers comprises simultaneously repositioning a plurality of sub-receivers associated with the receiver along respective sections of said trajectory.

7. The method of claim 1, wherein said procedure of obtaining a sequence of measurements of said RF signal at different positions along a trajectory by each of said receivers comprises simultaneously repositioning a plurality of receivers associated with a plurality of RF transmitters operating in different spectral ranges.

8. A system for determining a location of a radio frequency (RF) transmitter in the presence of multipath interference, the system comprising:

a plurality of RF receivers, spatially separated at known locations in a moderate multipath environment in the vicinity of said transmitter; and

a processor, coupled with said receivers, said processor operative for detecting an active RF signal associated with said transmitter received by at least one of said receivers and directing said receivers to acquire measurements of the detected RF signal, said processor further operative to calculate time difference of arrival (TDOA) measurements between pairs of said receivers based on a sequence of measurements of said RF signal obtained by each of said receivers at different positions along a trajectory, wherein said trajectory provides a plurality of measurements at relative phase differences between the direct-path and the multipath reflections of said detected RF signal, said processor further operative to average the TDOA measurements for each of said pairs of receivers to provide a respective updated TDOA measurement value, and further operative to determine a location of said transmitter based on the updated TDOA measurement values.

9. The system of claim 8, wherein said trajectory comprises a circular trajectory.

10. The system of claim 8, wherein said the range of said trajectory is at least half the wavelength of said detected RF signal.

11. The system of claim 8, further comprising repositioning means, operative to move at least one of said receivers to said different positions along a trajectory.

12. The system of claim 11, wherein said repositioning means is operative to repeatedly reposition said receiver multiple times over a selected trajectory pattern.

13. The system of claim 8, wherein said RF receivers comprises a plurality of receivers arranged or selectively deployed at fixed positions along said trajectory.

14. The system of claim 11, wherein said repositioning means is operative to simultaneously reposition a plurality of sub-receivers associated with said receiver along respective sections of said trajectory.

15. The system of claim 11, wherein said repositioning means is operative to simultaneously reposition a plurality of receivers associated with a plurality of RF transmitters operating in different spectral ranges.

16. The system of claim 11, wherein said repositioning means is selected from the list consisting of:

a shifting mechanism;

an automatic mechanical device;

a rotating device;

a mobile platform;

a vehicle;

a trolley; and

at least one person.

17. The system of claim 8, wherein said receivers are selected from the list consisting of:

a telecommunications receiver;

a cellular network receiver;

a spectrum management receiver; and

a broadcast receiver.