Spinning threat roll bearing estimator

• US 7,520,464 B1
• Filed: 01/04/2006
• Issued: 04/21/2009
• Est. Priority Date: 01/04/2005
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Van Allen, Russell N.
• Primary Examiner(s): Gregory; Bernarr E
• Application Number:
  US11/326,033
• Time in Patent Office: 1,203 Days
• Field of Search: 244 31- 33, 342/25.R, 342/25.A, 342/25.C, 342/61, 342/62, 342/104, 342/107, 342/113, 342/114, 342/118, 342/134, 342139-147, 342/156, 342/175, 342/195, 342417-449, 342/413, 342/461, 89/11.1
• US Class Current: 244/3.19
• CPC Class Codes: F41G 7/222 for spin-stabilized missiles
• CPC Class Codes: F41G 7/2253 Passive homing systems, i.e. comprising a receiver and do not requiring an active illumination of the target
• CPC Class Codes: F41G 7/2286 using radio waves
• CPC Class Codes: F42B 15/01 Arrangements thereon for guidance or control steering arrangements F42B10/60; aircraft flight control B64C; guidance systems other than those installed aboard F41G7/00, F41G9/00; locating by use of radio or other waves G01S; flight control in general G05D1/00; computer aspects G06]
• 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 3/52 using a receiving antenna moving, or appearing to move, in a cyclic path to produce a Doppler variation of frequency of the received signal

Abstract

An apparatus and method for determining a bearing from a spinning projectile to a target emitting electromagnetic radiation comprising disposing a plurality of electromagnetic radiation sensors on a body of the projectile, receiving sensed electromagnetic radiation from the plurality of sensors, determining a periodic phase modulation between pairs of the plurality of sensors, integrating the modulation over a plurality of revolutions of the projectile, and calculating a bearing estimate from the projectile to the target using the integration.

Claims

1. An apparatus for determining a bearing from a spinning projectile to a target emitting RF radiation, said apparatus comprising:

a plurality of RF radiation antennas disposed on a body of the projectile; and

a data processing element receiving RF radiation from said plurality of antennas, said element determining a periodic phase modulation between pairs of said plurality of antennas, integrating the modulated signal over a plurality of revolutions of the projectile, and calculating a bearing estimate from the projectile to the target using the integration of the modulated signal.

2. The apparatus of claim 1 wherein said antennas comprise an aperture narrower than a wavelength of the RF radiation.

3. The apparatus of claim 1 additionally comprising selectable front-end filters between said antennas and said data processing element.

4. The apparatus of claim 1 wherein said antennas number four.

5. The apparatus of claim 1 wherein said antennas are placed circumferentially around the body of the projectile.

6. The apparatus of claim 5 wherein when two of said antennas are centered on the target, the range difference between said two of said antennas is zero.

7. The apparatus of claim 1 wherein phase/gain mismatches between channels are nulled.

8. The apparatus of claim 1 wherein frequency of the RF radiation is 100 MHz to 300 GHz.

9. The apparatus of claim 1 wherein the projectile is a munition.

10. The apparatus of claim 1 wherein said apparatus provides a geolocation accuracy as to the target within 10 meters down to 100 MHz with 20 seconds of operation.

11. A method for determining a bearing from a spinning projectile to a target emitting electromagnetic radiation, the method comprising the steps of:

disposing a plurality of RF radiation antennas on a body of the projectile;

receiving RF radiation from the plurality of antennas;

determining a periodic phase modulation between pairs of the plurality of antennas;

integrating the modulated signal over a plurality of revolutions of the projectile; and

calculating a bearing estimate from the projectile to the target using the integration of the modulated signal.

12. The method of claim 11 wherein the antennas comprise an aperture narrower than a wavelength of the RF radiation.

13. The method of claim 11 additionally comprising the step of employing selectable front-end filters between the antennas and the data processing element.

14. The method of claim 11 wherein the antennas number four.

15. The method of claim 11 wherein in the disposing step the antennas are placed circumferentially around the body of the projectile.

16. The method of claim 15 wherein when two of the antennas are centered on the target, the range difference between the two of the antennas is zero.

17. The method of claim 11 wherein phase/gain mismatches between channels are nulled.

18. The method of claim 11 wherein frequency of the RF radiation is 100 MHz to 300 GHz.

19. The method of claim 11 wherein the projectile is a munition.

20. The method of claim 11 wherein the method provides a geolocation accuracy as to the target within 10 meters down to 100 MHz with 20 seconds of operation.