Distributed antenna system and method

• US 6,816,117 B2
• Filed: 05/24/2001
• Issued: 11/09/2004
• Est. Priority Date: 05/24/2001
• Status: Expired due to Fees

• Current Assignee: US Government As Represented By The Director National Security Agency
• Original Assignee: United States Administrator of National Aeronautics and Space Administration
• Inventors: Dobbins, Justin A., Fink, Patrick W.
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US09/867,993
• Publication Number:
  US 20020180641A1
• Time in Patent Office: 1,265 Days
• Field of Search: 342/357.11, 342/464
• US Class Current: 342/464
• CPC Class Codes: G01S 19/36 relating to the receiver frond end
• CPC Class Codes: G01S 19/42 Determining position
• CPC Class Codes: G01S 19/43 using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
• CPC Class Codes: G01S 19/55 Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method
• CPC Class Codes: H01Q 21/06 Arrays of individually energised antenna units similarly polarised and spaced apart

Abstract

System and methods are disclosed for employing one or more radiators having non-unique phase centers mounted to a body with respect to a plurality of transmitters to determine location characteristics of the body such as the position and/or attitude of the body. The one or more radiators may consist of a single, continuous element or of two or more discrete radiation elements whose received signals are combined. In a preferred embodiment, the location characteristics are determined using carrier phase measurements whereby phase center information may be determined or estimated. A distributed antenna having a wide angle view may be mounted to a moveable body in accord with the present invention. The distributed antenna may be utilized for maintaining signal contact with multiple spaced apart transmitters, such as a GPS constellation, as the body rotates without the need for RF switches to thereby provide continuous attitude and position determination of the body.

Claims

1. A method for utilizing a plurality of transmitters to determine one or more location characteristics of a body, said plurality of transmitters producing a plurality of RF carrier signals, said method comprising:

mounting one or more distributed antennas to said body, each of said one or more distributed antennas being comprised of at least one antenna element, at least one of said one or more distributed antennas having a plurality of phase centers such that said plurality of phase centers is equal in number to said plurality of transmitters from which said RF carrier signals are received, each phase center being associated with a respective one of said plurality of transmitters from which said respective RF carrier signals are received, a location of each of said plurality of phase centers being variable with respect to said at least one antenna element in response to a change of a relative orientation between said one or more distributed antennas and said plurality of transmitters;

receiving said plurality of RF carrier signals from said plurality of transmitters with said one or more distributed antennas; and

determining said one or more location characteristics of said body.

2. The method of claim 1, wherein said at least one antenna of said distributed antennas comprises a single continuous antenna radiator and said method further comprises simultaneously receiving all of said plurality of RF carrier signals from said single continuous antenna radiator.

3. The method of claim 1, wherein said one or more location characteristics comprises a position of said body.

4. The method of claim 1, wherein said one or more location characteristics comprises an attitude of said body.

5. The method of claim 1, wherein each of said one or more distributed antennas has a substantially spherical coverage.

6. The method of claim 1, wherein at least a portion of a view of said one or more transmitters by said one or distributed antennas is blocked by said body.

7. The method of claim 6, further comprising providing that each of said one or more distributed antennas are circularly constructed with a respective physical origin.

8. The method of claim 7, further comprising determining a vector from said respective physical origin to each said phase center associated with each of said respective one of said plurality of transmitters.

9. The method of claim 1, further comprising determining a distance between each respective one of said plurality of transmitters and each phase center associated therewith.

10. The method of claim 1, further comprising obtaining a coarse estimate of a position of said body, and utilizing said coarse estimate for determining a unit vector related to a first position vector of a physical center of said distributed antenna with respect to a reference system and a second position vector between said body and a respective of said plurality of satellites.

11. The method of claim 10, further comprising utilizing said unit vector for obtaining an improved estimate of a position of said body, and utilizing said improved estimate for iteratively determining said unit vector more accurately.

12. The method of claim 1, further comprising determining information related to a phase center constellation comprised of said plurality of phase centers.

13. The method of claim 12, further comprising determining a plurality of vector magnitudes whereby each vector magnitude is related to a vector from a physical center of said distributed antenna to one of said plurality of phase centers.

14. A method for utilizing a plurality of transmitters in a plurality of locations to determine one or more location characteristics of a body, said method comprising:

mounting one or more distributed antennas to said body, at least one of said one or more distributed antennas having a plurality of phase centers with respect to said plurality of locations of said plurality of transmitters, said plurality of phase centers being always equal in number to said plurality of transmitters from which respective transmitter signals are received from said plurality of transmitters by said at least one of said one or more distributed antennas, each of said plurality of phase centers being associated with a respective one of said plurality of transmitters from which said respective transmitter signals are received; and

determining one or more values related to said plurality of phase centers.

15. The method of claim 14, further comprising:

determining one or more values related to a vector to a reference center of said body with respect to a fixed coordinate system.

16. The method of claim 15, further comprising:

determining one or more values related to a position vector from said reference center to an i^th satellite.

17. The method of claim 16, further comprising:

determining one or more values related to a vector from said reference center to a phase center related to said i^th satellite.

18. The method of claim 17, further comprising:

determining an attitude vector for said body.

19. The method of claim 16, further comprising:

determining a unit vector for said body from said reference center with respect to an i^th satellite.

20. The method of claim 16, further comprising:

estimating a unit vector by obtaining an estimate of said position vector.

21. The method of claim 20, further comprising:

reducing the error of said estimate of said unit vector by iteration.

22. The method of claim 14, further comprising:

measuring a carrier phase from i^th satellite, and adding a correction to said measured carrier phase.

23. The method of claim 22, wherein said correction is determined utilizing a known attitude of said body.

24. The method of claim 22, wherein said correction is determined by making an approximation of said position vector.

25. A system for determining location characteristics of a body utilizing a plurality of spaced apart transmitters, said system comprising:

one or more antennas mounted to said body, each of said one or more antennas comprising at least one antenna element, at least one of said one or more antennas having a plurality of phase centers such that a location of each of said phase centers moves with respect to said at least one antenna element with variation of a relative orientation between said one or more antennas and said plurality of spaced apart transmitters; and

means for determining said location characteristics in response to reception of signals from said spaced apart transmitters by said one or more antennas.

26. The system of claim 25, wherein said means for determining said location characteristics comprises utilizing one or more equations related to calculating a carrier phase.

27. The system of claim 25, wherein said means for determining said location characteristics utilizes the following equation:

28. The system of claim 25, wherein said means for determining said location characteristics utilizes the following equation. $$

vi

=

rsi-rB

-rpi·

rsi-rB

rsi-rB

29. The system of claim 25, wherein said means for determining said location characteristics utilizes the following equation.

30. The system of claim 25, wherein said means for determining said location characteristics utilizes the following equation. ${\tilde{\hat{r}}}_{\mathrm{sib}}\approx$

rsi-r~b

rsi-r~b

31. The system of claim 25, wherein said means for determining said location characteristics utilizes the following equation.

32. The system of claim 25, wherein said means for determining said location characteristics utilizes the following equation.

33. A radiator system for determining location characteristics of a body utilizing a plurality of spaced apart transmitters, said body comprising a surface defining a periphery of said body, said periphery extending around said body, said radiator system comprising:

a continuous wrap-around antenna element mounted with respect to said periphery of said body, said continuous wrap-around antenna element having a plurality of phase centers such that said plurality of phase centers is equal in number to said plurality of spaced apart transmitters from which respective transmitter signals are received from said plurality of transmitters by said continuous wrap-around antenna element, each of said plurality of phase centers being associated with a respective one of said plurality of transmitters from which said respective transmitter signals are received.

34. The radiator system of claim 33, wherein said continuous wrap-around antenna element comprises a first circular ring.

35. The radiator system of claim 34, further comprising a second circular ring.

36. The radiator system of claim 33, wherein said continuous wrap-around antenna element extends more than 180°

around said periphery of said body.

37. The radiator system of claim 33, wherein said continuous wrap-around antenna element is operable for maintaining continuous contact with said plurality of spaced apart transmitters as said body rotates even when said body obscures a view of said one or more spaced apart transmitters from a portion of said continuous wrap around antenna element.

38. The radiator system of claim 33, further comprising means for determining an attitude of said body utilizing no more than two of said continuous wrap-around antenna elements wherein said body has three degrees of freedom.

39. The radiator system of claim 33, further comprising means for determining an attitude of said body utilizing no more than said continuous wrap-around antenna element wherein said body has two degrees of freedom.

40. A method for carrier phase determination of location characteristics utilizing a plurality of spaced apart transmitters, comprising:

mounting one or more antennas to a moveable body positioned among said plurality of spaced apart transmitters such that said one or more antennas maintain contact with each of said plurality of spaced apart transmitters as said attitude of said body changes without utilizing RF switches, each of said one or more antennas being comprised of at least one antenna element, at least one of said one or more antennas having a plurality of phase centers, a location of said plurality of phase centers being moveable with respect to said at least one antenna element in response to a variation of a relative orientation between said one or more antennas and said plurality of transmitters; and

determining one or more values related to one or more of said plurality of phase centers of said one or more antennas.

41. The method of claim 40, further comprising determining an attitude solution for said body when said body has three degrees of freedom utilizing no more than two antennas.

42. The method of claim 40, further comprising determining an attitude solution for said body when said body has two degrees of freedom utilizing no more than one antenna.

43. The method of claim 40, further comprising providing that said one or more antennas has wide angle coverage for simultaneous contact with said plurality of spaced apart transmitters.