Distributed elevated radar antenna system

• US 6,677,890 B2
• Filed: 06/03/2002
• Issued: 01/13/2004
• Est. Priority Date: 06/03/2002
• Status: Active Grant

• Current Assignee: Information Systems Laboratories, Inc.
• Original Assignee: Information Systems Laboratories, Inc.
• Inventors: Boschma, James, Halsey, J. Doss
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): ALSOMIRI, ISAM A
• Application Number:
  US10/161,294
• Publication Number:
  US 20030222811A1
• Time in Patent Office: 589 Days
• Field of Search: 342/73-77, 342/88, 342/89
• US Class Current: 342/74
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 7/003 Transmission of data between radar, sonar or lidar systems and remote stations
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 25/00 Antennas or antenna systems providing at least two radiating patterns arrangements for changing or varying the orientation or the shape of the directional pattern H01Q3/00

Abstract

An airborne radar antenna system for detecting a target in a volume includes a tethered aerostat and an antenna that is supported above ground by the aerostat. The aerostat-based antenna is used for transmitting and receiving a radar beam into the volume to detect the target. Additionally, the system includes a ground-based transmitter that generates a beacon signal which monitors the antenna configuration at the aerostat. A computer then evaluates the beacon signal to create an error signal which is used to maintain a predetermined configuration for the antenna. The system also includes mechanisms for orienting the radar beam along preselected beam paths between the antenna and the volume.

Claims

1. An airborne radar antenna system for detecting a target in a volume which comprises:

an aerostat;

a tether attached to said aerostat for anchoring said aerostat to a point on the ground;

an antenna for transmitting and receiving a radar beam, said antenna being supported by said aerostat at a location above ground level;

a means for radiating a beacon signal between said antenna and a ground-based beacon;

a computer means for evaluating said beacon signal to create an error signal as said beacon signal is received by said antenna; and

electronic means for configuring said antenna in response to said error signal to orient said radar beam along a preselected beam path between said antenna and said volume.

2. A system as recited in claim 1 further comprising means for spinning said antenna to sweep said radar beam through said volume.

3. A system as recited in claim 1 wherein said aerostat includes a buoyancy chamber and wherein said antenna is mounted inside said chamber of said aerostat.

4. A system as recited in claim 1 wherein said antenna comprises:

a flexible sheet;

a plurality of antenna elements printed on said flexible sheet; and

means for rigidly mounting said flexible sheet on said aerostat.

5. A system as recited in claim 1 wherein said tether has a first end and a second end, with said first end fixed to said point at ground level and wherein said system further comprises:

a plurality of interconnecting lines attached between said aerostat and said second end of said tether to secure said aerostat thereto; and

an enclosure attached to said second end of said tether with said antenna mounted inside said enclosure.

6. A system as recited in claim 1 further comprising:

a ground station with said computer means and said electronic means positioned at said ground station; and

a communications link connecting said computer means and said electronic means at said ground station with said antenna at said aerostat.

7. A system as recited in claim 6 wherein said communications link is an optical fiber.

8. A system as recited in claim 1 wherein said antenna establishes a transmit aperture (of area A₁) for transmitting said radar beam and a receive aperture (of area A₂) for receiving multiple-simultaneous receive beams covering the volume from said radar beam, wherein A₁ is related to A₂ by the expression A₁=nA₂ where “

n”

is a number greater than 1 (n>

1), and wherein “

x”

seconds are required to detect said target when n=1, said system further comprises means for increasing a dwell time of said antenna to “

nx”

seconds for receiving said receive beams to keep a same volumetric search rate.

9. A system as recited in claim 1 further comprising a plurality of said aerostats.

10. An airborne radar antenna system for detecting a target in a volume which comprises:

an inflatable buoyancy chamber;

a support means attached to said buoyancy chamber;

a flexible printed circuit radar antenna with a power source, mounted on said support means for transmitting and receiving a radar beam;

a means for selectively positioning said buoyancy chamber at a predetermined location above ground level;

a ground-based transmitter for radiating a beacon signal toward said antenna for receipt by said antenna;

a computer means for evaluating said beacon signal to create an error signal as said beacon signal is received by said antenna;

electronic means for configuring said antenna in response to said error signal to orient said radar beam along a preselected beam path between said antenna and said volume; and

a means for spinning said antenna to sweep said radar beam through said volume for detection of said target.

11. A system as recited in claim 10 wherein said positioning means comprises:

a tether attached to said buoyancy chamber for anchoring said buoyancy chamber to a point on the ground; and

a winch positioned at said point on the ground, said winch being operable to vary a length of said tether between said buoyancy chamber and said point on the ground.

12. A system as recited in claim 11 further comprising:

a ground station with said computer means and said electronic means positioned at said ground station; and

a communications link connecting said computer means and said electronic means at said ground station with said antenna at said buoyancy chamber.

13. A system as recited in claim 12 wherein said communications link is an optical fiber attached to said tether.

14. A system as recited in claim 10 wherein said support means is mounted inside said buoyancy chamber.

15. A system as recited in claim 10 wherein said antenna establishes a transmit aperture (of area A₁) for transmitting said radar beam and a receive aperture (of area A₂) for receiving multiple-simultaneous receive beams covering the volume from said radar beam, wherein A₁ is related to A₂ by the expression A₁=nA₂ where “

n”

is a number greater than 1 (n>

1), and wherein “

x”

seconds are required to detect said target when n=1, said system further comprises means for increasing a dwell time of said antenna to “

nx”

seconds for receiving said receive beams to keep a same volumetric search rate.

16. A method for employing an airborne radar antenna system to detect a target in a volume which comprises the steps of:

inflating an aerostat;

anchoring said aerostat to a point on the ground;

supporting an antenna with said aerostat at a location above ground level for transmitting and receiving a radar beam;

radiating a beacon signal from a ground-based transmitter toward said antenna for receipt by said antenna;

using a computer to evaluate said beacon signal to create an error signal as said beacon signal is received by said antenna; and

electronically reconfiguring said antenna in response to said error signal to orient said radar beam along a preselected beam path between said antenna and said volume.

17. A method as recited in claim 16 further comprising the step of spinning said antenna to sweep said radar beam through said volume.

18. A method as recited in claim 17 wherein said antenna establishes a transmit aperture (of area A₁) for transmitting said radar beam and a receive aperture (of area A₂) for receiving multiple-simultaneous receive beams covering the volume from said radar beam, wherein A₁ is related to A₂ by the expression A₁=nA₂ where “

n”

is a number greater than 1 (n>

1), and wherein “

x”

seconds are required to detect said target when n=1, and wherein said method further comprises the step of increasing a dwell time of said antenna to “

nx”

seconds for receiving said receive beams to keep a same volumetric search rate.

19. A method as recited in claim 16 further comprising the step of employing a plurality of said aerostats.