METHODS, APPARATUSES AND SYSTEMS FOR LOCATING NON-COOPERATIVE OBJECTS

• US 20090167607A1
• Filed: 07/26/2006
• Published: 07/02/2009
• Est. Priority Date: 07/27/2005
• Status: Active Grant

• Current Assignee: Propagation Research Associates, Inc.
• Original Assignee: Propogation Research Associates Incorporated
• Inventors: Holder, Ernest Jefferson
• Granted Patent: US 8,120,526 B2
• Time in Patent Office: Days
• US Class Current: 342/453
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 5/0273 using multipath or indirect path propagation signals in position determination

Abstract

Measurements of the differential and/or absolute time-of-arrival of separable signals transmitted from a set of spatially-distributed (SD) transmitters are obtained by one or more receivers. The signals transmitted by each transmitter are made separable by encoding them in a manner that enables each signal to be distinguished from the others by the receiver or receivers. An accurate time-of-arrival of each signal at the receiver is determined, from which the path lengths from the transmitters to the receiver and from the receiver to the object are determined based on the known propagation speed of the signals. Any Doppler frequency shifts in each signal can also be determined from this information. From all of this information, the receiver is able to determine its own position, motion and orientation (roll, pitch and yaw), as well as the position and motion of the moving object being tracked by the receiver.

Claims

1. A system for locating one or more non-cooperative objects, the system comprising:

a spatially-distributed (SD) transmitter system comprising at least first and second transmitters that are spatially separated from each other, each transmitter transmitting a coded signal, the coded signals being coded with different codes that enable the coded signals to be distinguishable from each other; and

at least a first receiver, the first receiver being configured to receive the coded signals and separate the coded signals from one another, the received coded signals including coded signals transmitted by the transmitters without being reflected by a non-cooperative object and coded signals transmitted by the transmitters that have been reflected by the non-cooperative object, the receiver including a processor that processes the separated signals to determine at least a position of the non-cooperative object relative to the receiver.

2. The system of claim 1, wherein when the processor of the receiver processes the separated coded signals, the processor also determines an angular position of the receiver relative to the SD transmitter system.

3. The system of claim 2, wherein when the processor of the receiver processes the separated coded signals, the processor also determines an angular position of the object relative to the SD transmitter system.

4. The system of claim 3, wherein when the processor of the receiver processes the separated coded signals, the processor also determines a range of the object from the receiver.

5. The system of claim 1, wherein the receiver and the SD transmitter system are at fixed positions relative to each other.

6. The system of claim 2, wherein when the processor of the receiver processes the separated coded signals, the processor also determines the motion of the receiver relative to the SD transmitter system.

7. The system of claim 6, wherein when the processor of the receiver processes the separated coded signals, the processor also determines a pitch, roll and yaw of the receiver.

8. The system of claim 1, wherein when the processor of the receiver processes the separated coded signals, the processor also determines a velocity of the object.

9. The system of claim 1, wherein the processor of the receiver determines at least the position of the object relative to the receiver by:

determining a time-of-arrival (TOA) of each of the coded signals;

calculating a difference between the TOAs, by dividing the difference by a known propagation speed of the coded signals to obtain a respective path length from each of said first and second transmitters to the receiver;

using the path lengths to determine a range from the receiver to a phase center of the SD transmitter system and an angular position of the receiver relative to a phase center of the SD transmitter system; and

using one or more of the path lengths, the range and the angular position to determine a range from the receiver to the object and an angular position of the object relative to the receiver.

10. The system of claim 1, wherein the transmitted signals are coded with codes that are orthogonal or at least nearly orthogonal to each other.

11. The system of claim 1, wherein the SD transmitter further comprises at least a third transmitter that is spatially separated from the first and second transmitters, the third transmitter transmitting a coded signal, the coded signal transmitted by the third transmitter being coded with a code that is different from the codes that are used to code the coded signals transmitted by the first and second transmitters to enable all of the coded signals to be distinguishable from each other, and wherein the processor of the receiver processes the separated coded signals to determine at least a position of the object relative to the receiver, a velocity of the object, and a range from the receiver to the object.

12. The system of claim 1, wherein the receiver is mounted on a mobile platform that uses the position of the object determined by the processor to locate and track the object.

13. The system of claim 1, further comprising:

at least a second receiver, the second receiver being configured to receive the coded signals and separate the coded signals from one another, the received coded signals including coded signals transmitted by the transmitters without being reflected by the object and coded signals transmitted by the transmitters that have been reflected by the object, the second receiver including a processor that processes the separated coded signals to determine at least a position of the object relative to a phase center of the first and second receivers, a velocity of the object, and a range of the object from the phase center of the first and second receivers.

14. The system of claim 13, wherein the system is capable of simultaneously determining at least respective positions of multiple respective non-cooperative objects.

15. A method for locating one or more non-cooperative objects comprising:

receiving two or more coded signals in a receiver, the coded signals being transmitted by two or more transmitters of a spatially-distributed (SD) transmitter system, the coded signals being coded with different codes that enable the coded signals to be distinguishable from each other, the received coded signals including coded signals transmitted by the transmitters without being reflected by a non-cooperative object and coded signals transmitted by the transmitters that have been reflected by the cooperative object;

in the receiver, separating the coded signals from one another; and

in a processor of the receiver, processing the separated signals to determine at least a position of the object relative to the receiver.

16. The method of claim 15, wherein said processing the separated signals by the processor comprises:

determining a time-of-arrival (TOA) of each of the coded signals;

calculating a difference between the TOAs;

dividing the difference by a known propagation speed of the coded signals to obtain a respective path length from each of the first and second transmitters to the receiver;

using the path lengths to determine a range from the receiver to a phase center of the SD transmitter system and an angular position of the receiver relative to a phase center of the SD transmitter system; and

using one or more of the path lengths, the range and the angular position to determine a range from the receiver to the object and an angular position of the object relative to the receiver.

17. The method of claim 15, wherein when the processor of the receiver processes the separated coded signals, the processor also determines an angular position of the receiver relative to the SD transmitter system.

18. The method of claim 17, wherein when the processor of the receiver processes the separated coded signals, the processor also determines an angular position of the object relative to the SD transmitter system.

19. The method of claim 18, wherein when the processor of the receiver processes the separated coded signals, the processor also determines a range of the object from the receiver.

20. The method of claim 15, wherein the receiver and the SD transmitter system are at fixed positions relative to each other.

21. The method of claim 17, wherein when the processor of the receiver processes the separated coded signals, the processor also determines the motion of the receiver relative to the SD transmitter system.

22. The method of claim 15, wherein when the separated signals are processed by the processor, the processor also determines a pitch, roll and yaw of the receiver.

23. The method of claim 15, wherein the transmitted signals are coded with codes that are orthogonal or at least nearly orthogonal to each other.

24. The method of claim 15, wherein the receiver is mounted on a mobile platform that uses the position of the object determined by the processor to locate and track the object.

25. A system for locating one or more non-cooperative objects, the system comprising:

a spatially-distributed (SD) transmitter system comprising at least first and second transmitters that are spatially separated from each other, each transmitter transmitting a coded signal, the coded signals being coded with different codes that enable the coded signals to be distinguishable from each other; and

at least a first receiver, the first receiver being configured to receive the coded signals and separate the coded signals from one another, the received coded signals including coded signals transmitted by the transmitters without being reflected by a non-cooperative object and coded signals transmitted by the transmitters that have been reflected by the non-cooperative object, the receiver including a processor that processes the separated signals to determine at least an angular position of the non-cooperative object relative to the SD transmitter system and an angular position of the receiver relative to the SD transmitter system.

26. The system of claim 25, wherein when the processor of the receiver processes the separated coded signals, the processor also determines a range of the receiver relative to the SD transmitter system.

27. The system of claim 26, wherein when the processor of the receiver processes the separated coded signals, the processor also determines an angular position of the object relative to the receiver.

28. A computer program for locating one or more noncooperative objects, the program being stored on a computer-readable medium, the program comprising:

instructions for separating two or more coded signals transmitted by two or more respective transmitters of a spatially-distributed (SD) transmitter system, the coded signals being coded with different codes that enable the coded signals to be distinguishable from each other, the received coded signals including coded signals transmitted by the transmitters without being reflected by a non-cooperative object and coded signals transmitted by the transmitters that have been reflected by the non-cooperative object; and

instructions for processing the separated signals to determine at least a position of the object relative to the receiver.

29. The program of claim 28, wherein the instructions for processing the separated signals to determine at least a position of the object relative to the receiver comprise:

instructions that process the separated signals to determine a time-of-arrival (TOA) of each of the coded signals;

instructions that process the TOAs to calculate a difference between the TOAs;

instructions that divide the difference by a known propagation speed of the coded signals to obtain a respective path length from each of the first and second transmitters to the receiver;

instructions that process the path lengths to determine a range from the receiver to a phase center of the SD transmitter system and an angular position of the receiver relative to a phase center of the SD transmitter system; and

instructions that process one or more of the path lengths, the range and the angular position to determine a range from the receiver to the object and an angular position of the object relative to the receiver.