Tracking arrangement for a communications system on a mobile platform

• US 7,956,806 B2
• Filed: 06/15/2009
• Issued: 06/07/2011
• Est. Priority Date: 06/15/2009
• Status: Expired due to Fees

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Space & Mission Systems Corporation (Northrop Grumman Corporation)
• Inventors: Shreve, Gregory A., Liu, Zhang
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): LIU, HARRY K
• Application Number:
  US12/484,604
• Publication Number:
  US 20100315288A1
• Time in Patent Office: 722 Days
• Field of Search: 342/359
• US Class Current: 342/359
• CPC Class Codes: G01S 3/40 adjusting orientation of a single directivity characteristic to produce maximum or minimum signal, e.g. rotatable loop antenna or equivalent goniometer system
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming

Abstract

Systems and methods are provided for orienting an antenna in a communications system on a mobile platform to orient a peak of the antenna pattern in a direction associated with a signal source. A signal from a signal source is received at the antenna. A signal strength is measured from the received signal. A signal strength and a misalignment of the antenna along at least one axis are predicted according to a previous estimate of the signal strength, a previous estimate of the misalignment of the antenna, an estimated change in the signal strength, and a known change in the antenna orientation. The predicted signal strength and misalignment of the antenna are updated according to the measured signal strength to provide an estimate of a current misalignment of the antenna. The orientation of the peak of the antenna pattern is adjusted according to the estimated current misalignment of the antenna.

Claims

1. A method for orienting an antenna in a communications system on a mobile platform to orient a peak of the antenna pattern in a direction associated with a signal source comprising:

receiving a signal from a signal source at the antenna;

measuring a signal strength from the received signal;

predicting a signal strength and a misalignment of the antenna along at least one axis according to a previous estimate of the signal strength, a previous estimate of the misalignment of the antenna, an estimated change in the signal strength, and a known change in the antenna orientation;

updating the predicted signal strength and misalignment of the antenna according to the measured signal strength to provide an estimate of a current misalignment of the antenna; and

adjusting the orientation of the peak of the antenna pattern according to the estimated current misalignment of the antenna.

2. The method of claim 1, wherein updating the predicted signal strength and misalignment of the antenna further comprises updating the predicted signal strength and misalignment of the antenna according to data from an inertial measurement unit.

3. The method of claim 1, wherein updating the predicted signal strength and misalignment of the antenna further comprises updating the predicted signal strength and misalignment of the antenna according to data from an attitude reference sensor.

4. The method of claim 1, wherein updating the predicted signal strength and misalignment of the antenna further comprises updating the predicted signal strength and misalignment of the antenna according to data from a global positioning system.

5. The method of claim 1, wherein predicting a signal strength and a misalignment of the antenna along at least one axis comprises estimating the signal strength as a state in a Kalman filter.

6. The method of claim 1, further comprising determining a position of the signal source, orienting a peak of the antenna pattern toward the determined position, and scanning the antenna pattern peak across at least one axis until a signal is received.

7. The method of claim 1, wherein adjusting the orientation of the peak of the antenna pattern according to the estimated current misalignment comprises mechanically altering the orientation of the antenna.

8. The method of claim 1, wherein adjusting the orientation of the peak of the antenna pattern according to the estimated current misalignment comprises changing a power provided to at least one active element of the antenna.

9. A communications system configured to allow communications between a mobile platform and a signal source comprising:

an antenna assembly comprising an antenna;

a modem configured to determine a signal strength of a signal received at the antenna;

an attitude control assembly that is configured to employ a Kalman filter to estimate a misalignment of the antenna from a plurality of parameters comprising at least the determined signal strength, an orientation of the antenna at a previous time, an estimated signal strength at the previous time, and an estimated change in the signal strength; and

an orientation system configured to alter the orientation of the antenna according to the estimated current orientation at the Kalman filter.

10. The communications system of claim 9, the orientation system comprising a motorized platform that is configured to physically adjust the orientation of the antenna along at least one of an azimuth angle and an elevation angle.

11. The communications system of claim 9, further comprising an inertial measurement unit configured to determine a change in the position of the antenna assembly and provide the determined change in position to the attitude control assembly.

12. The communications system of claim 9, further comprising an attitude reference sensor configured to determine a change in the orientation of the antenna assembly and provide the determined change in orientation to the attitude control assembly.

13. The communications system of claim 9, further comprising a global positioning system configured to determine an absolute position of the mobile platform and provide the determined position to the attitude control assembly.

14. The communications system of claim 9, the mobile platform comprising an aircraft.

15. The communications system of claim 9, the mobile platform comprising a ground vehicle.

16. The communications system of claim 9, the signal source comprising a satellite relay.

17. A computer readable medium storing executable instructions configured to determine a misalignment of a peak response of an antenna from a signal source, the executable instructions comprising:

a modem interface configured to measure a signal strength from a signal received at the antenna;

a Kalman filter configured to predict a signal strength and a misalignment of the antenna along at least one axis as a state of the Kalman filter and update each of the predicted signal strength and misalignment of the antenna according to the measured signal strength to provide an estimate of a current misalignment of the antenna; and

an attitude control element configured to provided instructions to an antenna assembly as to adjust the orientation of the peak of the antenna pattern according to the estimated current misalignment of the antenna.

18. The computer readable medium of claim 17, further comprising a database indicting the position of the signal source for a plurality of times, the attitude control element utilizing the database for an initial orientation of the antenna.

19. The computer readable medium of claim 17, further comprising a sensor interface that receives data from at least one of an attitude reference sensor and an internal measurement unit and determines a position and orientation of the antenna in an antenna reference frame, the Kalman filter being configured update each of the predicted signal strength and misalignment of the antenna according to the measured signal strength and the determined position and orientation to provide an estimate of a current misalignment of the antenna.

20. The computer readable medium of claim 17, further comprising a vehicle systems interface that receives data from at least one system associated with the mobile platform and provides the data to the Kalman filter.