Multi-static UAV radar system for mode-adaptive propagation channels with obscured targets

• US 6,653,970 B1
• Filed: 11/12/2002
• Issued: 11/25/2003
• Est. Priority Date: 11/12/2002
• Status: Expired due to Fees

• Current Assignee: The Government of United States As Represented By The Secretary of The Air Force
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Mitra, Atindra
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US10/295,551
• Time in Patent Office: 378 Days
• Field of Search: 342/22, 342/25, 342/52, 342/58, 342/59, 342/90, 342/179, 342/190, 342/191, 342/357.06, 342/357.08, 342/357.09
• US Class Current: 342/22
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/88 Radar or analogous systems specially adapted for specific applications electromagnetic prospecting or detecting of objects, e.g. near-field detection, G01V3/00
• CPC Class Codes: G01S 13/9058 Bistatic or multistatic SAR
• CPC Class Codes: G01V 3/17 operating with electromagnetic waves operating with millimetre waves G01V8/005

Abstract

Bistatic radar compatible for investigating the employment of a high-altitude UAV working in tandem with a group of low-altitude UAVs. The bistatic radar is divided into a position-adaptive bistatic mode and a close-range monostatic mode. In position-adaptive (robotic) bistatic mode, each low-altitude UAV estimates a new parameter denoted as the differential path length to adaptively implement self-adjustments in position. This approach provides each UAV with the potential for looking down the “throat” of an obscuration channel. In the event that a particular low-altitude UAV detects an obscuration channel, the low-altitude UAV will transfer to a close-range monostatic mode in an effort to interrogate the obscuration channel for targets.

Claims

1. A multi-mode, radar method for detecting targets in difficult and obscured environments comprising the steps of:

transmitting a signal through a channel from a high altitude unmanned air vehicle;

passively receiving said signal from said transmitting step through a plurality of unmanned air vehicles at a low altitude platform relative to said unmanned air vehicle from said transmitting step,

determining a differential signal time delay from a time said signal is transmitted at said transmitting step and a time said signal is received at said receiving step, said differential time delay indicating a differential time path obstruction between said high altitude unmanned air vehicle and said unmanned air vehicle at said low altitude platform;

monitoring said signal time delay by said low altitude platform unmanned air vehicles and converging to a point that corresponds to a minimum time delay; and

detecting targets within said differential time path at said point of minimum time delay by an unmanned air vehicle at a low altitude platform.

2. The multi-mode, radar method of claim 1 for detecting targets in difficult and obscured environments wherein said transmitting step further comprises transmitting a signal through a rectangular wave guide channel from a high altitude unmanned air vehicle.

3. The multi-mode, radar method of claim 1 for detecting targets in difficult and obscured environments wherein said transmitting step further comprises transmitting a signal through a horizontal cavity embedded in a ground plane wave guide channel from a high altitude unmanned air vehicle.

4. The multi-mode, radar method of claim 1 for detecting targets in difficult and obscured environments wherein said transmitting step further comprises transmitting a signal through a vertically oriented cavity on a slant plane wave guide channel from a high altitude unmanned air vehicle.

5. The multi-mode, radar method of claim 1 for detecting targets in difficult and obscured environments wherein said transmitting step further comprises transmitting a signal through an array of vertical cylinders wave guide channel from a high altitude unmanned air vehicle.

6. The multi-mode, radar method of claim 1 for detecting targets in difficult and obscured environments wherein said transmitting step further comprises transmitting a signal through a network of paths and junctions associated with urban structures wave guide channel from a high altitude unmanned air vehicle.

7. The multi-mode, radar method of claim 1 for detecting targets in difficult and obscured environments further comprising the step of maintaining signal coherence between said transmitted and received signal.

8. The multi-mode, radar method of claim 7 for detecting targets in difficult and obscured environments wherein said step of maintaining signal coherence between said transmitted and received signal comprises synchronization methods that include sampling the direct path signal from the high-altitude UAV to the low-altitude UAV.

9. The multi-mode, radar method of claim 7 for detecting targets in difficult and obscured environments wherein said step of maintaining signal coherence between said transmitted and received signal comprises synchronization methods that include determining the location of the receiver with respect to the transmitter via GPS data.

10. A multi-mode radar system for environments with difficult and obscured targets comprising:

an irradiating unmanned air vehicle positioned at the first end of an open-ended wave guide;

a plurality of passive receiving unmanned air vehicles at a low altitude platform relative to said irradiating unmanned air vehicle and positioned at a second, opposing end of an open-ended wave guide, a signal from said irradiating unmanned air vehicle transmitted to and received by one or more of said plurality of passive receiving unmanned air vehicles; and

processing means for determining a differential time delay from a time said signal is transmitted and a time said signal is received, said differential time delay indicating a differential time path obstruction.

11. The multi-mode radar system of claim 10 for environments with difficult and obscured targets further comprising monitoring means for determining a minimum differential time delay whereby said plurality of passive receiving unmanned air vehicles at a low altitude platform converge to detect a target.

12. The multi-mode radar system of claim 10 for environments with difficult and obscured targets further comprising an irradiating unmanned air vehicle positioned at the first end of an open-ended rectangular wave guide.

13. The multi-mode radar system of claim 10 for environments with difficult and obscured targets further comprising an irradiating unmanned air vehicle positioned at the first end of an open-ended horizontal cavity embedded in a ground plane wave guide channel.

14. The multi-mode radar system of claim 10 for environments with difficult and obscured targets further comprising an irradiating unmanned air vehicle positioned at the first end of a vertically oriented cavity on a slant plane wave guide channel.

15. The multi-mode radar system of claim 10 for environments with difficult and obscured targets further comprising an irradiating unmanned air vehicle positioned at the first end of an array of vertical cylinders wave guide channel.

16. The multi-mode radar system of claim 10 for environments with difficult and obscured targets of claim 10 further comprising an irradiating unmanned air vehicle positioned at the first end of a network of paths and junctions associated with urban structures wave guide channel.

17. The multi-mode radar system of claim 10 for environments with difficult and obscured targets further comprising means for maintaining signal coherence between said transmitted and received signal.

18. The multi-mode radar system of claim 10 for environments with difficult and obscured targets further comprising means for maintaining signal coherence between said transmitted and received signal.

19. The multi-mode radar system of claim 18 for environments with difficult and obscured targets further comprising maintaining signal coherence between said transmitted and received signal comprises synchronization methods that include sampling the direct path signal from the high-altitude UAV to the low-altitude UAV.

20. The multi-mode radar system of claim 18 for environments with difficult and obscured targets further comprising means for maintaining signal coherence between said transmitted and received signal comprises synchronization methods that include determining the location of the receiver with respect to the transmitter via GPS data.