Systems and methods for reducing directional interference based on adaptive excision and beam repositioning
Systems and methods are provided for repositioning a directional antenna that responds to a desired signal and directional interference. The antenna can generate a sum beam and first and second difference beams. Respective powers of the sum beam and the first and second difference beams can be determined. At least a portion of any of the directional interference can be excised from the sum beam and the first and second difference beams. Measures of the directional interference can be determined in the sum beam and the first and second difference beams. A first correlation between the sum beam and the first and second difference beams can be generated. Additional correlations between a signal identifier and the sum beam and first and second beams monitor the desired signal reception. The antenna can be repositioned away from the directional interference based on the powers, the measures, and the first correlation.
1. A system for repositioning a directional antenna that responds to a desired signal and directional interference, the antenna generating a sum beam and first and second difference beams, the system comprising:
an antenna positioner coupled to the directional antenna;
a controller coupled to the antenna positioner;
power detectors respectively configured to output to the controller powers of the sum beam and the first and second difference beams;
excision circuits respectively configured to (a) excise at least a portion of the directional interference from the sum beam and the first and second difference beams and (b) output to the controller a measure of the directional interference in that beam; and
a first correlator configured to output to the controller a first correlation between the sum beam and the first and second difference beams,
wherein the controller is configured to control the antenna positioner so as to reposition the antenna away from the directional interference based on the powers, the measures, and the first correlation.
2. The system of claim 1 , wherein each of the excision circuits is configured to:
digitize the sum beam or the first or second difference beam;
provide as output a set of spectral bins for that beam spanning a bandwidth of the desired signal, each bin having a respective power level, at least one bin including the interference;
compare a collective power level of the bins to a predetermined threshold; and
based upon the collective power level exceeding the predetermined threshold, excise at least one bin that includes the interference.
3. The system of claim 2 , wherein the measures comprise the power levels of the bins from the digitized first difference beam, the power levels of the bins from the digitized second difference beam, and the power levels of the bins from the digitized sum beam.
4. The system of claim 3 , wherein the controller is configured to control the antenna positioner so as to reposition the antenna based on:
a distance between the interference and the desired signal in a first plane determined based on a ratio of the power levels of the bins from the digitized first difference beam and the power levels of the bins from the digitized sum beam; and
a distance between the interference and the desired signal in a second plane determined based on a ratio of the power levels of the bins from the digitized second difference beam and the power levels of the bins from the digitized sum beam, the second plane being orthogonal to the first plane.
5. The system of claim 4 , wherein the wherein the controller is configured to control the antenna positioner so as to reposition the antenna further based on a sign of the first correlation indicating a direction of the interference in the first and second planes.
6. The system of claim 2 , wherein the predetermined threshold is selected such that the collective power of the spectral bins following excision is sufficiently low to maintain linear operation of the system.
7. The system of claim 1 , wherein the controller is configured to control the antenna positioner so as to reposition the antenna to place the directional interference within a null between a main beam and a sidelobe of the main beam.
8. The system of claim 1 , wherein the controller further is configured to:
based upon the measures being below a threshold, control the antenna positioner so as to track the desired signal in a closed loop;
based upon the measures exceeding the threshold, control the antenna positioner so as to cease tracking the desired signal; and
after controlling the antenna positioner so as to reposition the antenna away from the directional interference, control the antenna positioner so as to resume tracking the desired signal in a closed loop so as to sufficiently maintain power of the desired signal received by the antenna while sufficiently reducing power of the directional interference received by the antenna.
9. The system of claim 1 , wherein the desired signal further includes a signal identifier, the system further comprising:
a second correlator configured to output to the controller a second correlation between the signal identifier and the sum beam; and
third and fourth correlators respectively configured to output to the controller third and fourth correlations between the signal identifier and the first and second difference beams,
wherein the controller further is configured to control the antenna positioner so as to reposition the antenna away from the directional interference based on the second, third, and fourth correlations.
10. The system of claim 9 , wherein the signal identifier comprises a pseudorandom code added to the desired signal.
11. The system of claim 9 , wherein the signal identifier comprises an existing feature of the desired signal wherein the existing feature is a frame format, preamble, or other characteristics unique to the desired signal.
12. A method for repositioning a directional antenna that responds to a desired signal and directional interference, the antenna generating a sum beam and first and second difference beams, the method comprising:
determining respective powers of the sum beam and the first and second difference beams;
excising at least a portion of the directional interference from the sum beam and the first and second difference beams;
determining measures of the directional interference in the sum beam and the first and second difference beams;
generating a first correlation between the sum beam and the first and second difference beams; and
repositioning the antenna away from the directional interference based on the powers, the measures, and the first correlation.
13. The method of claim 12 , wherein the excising comprises:
digitizing the sum beam and the first and second difference beams;
generating a set of spectral bins for that digitize beam spanning a bandwidth of the desired signal, each bin having a respective power level, at least one bin including the interference;
comparing a collective power level of the bins to a predetermined threshold; and
based upon the collective power level exceeding the predetermined threshold, excising at least one bin that includes the interference.
14. The method of claim 13 , wherein the measures comprise the power levels of the bins from the digitized first difference beam, the power levels of the bins from the digitized second difference beam, and the power levels of the bins from the digitized sum beam.
15. The method of claim 14 , wherein the antenna is repositioned based on:
a distance between the interference and the desired signal in a first plane determined based on a ratio of the power levels of the bins from the digitized first difference beam and the power levels of the bins from the digitized sum beam; and
a distance between the interference and the desired signal in a second plane determined based on a ratio of the power levels of the bins from the digitized second difference beam and the power levels of the bins from the digitized sum beam, the second plane being orthogonal to the first plane.
16. The method of claim 15 , wherein the antenna is repositioned further based on a sign of the first correlation indicating a direction of the interference in the first and second planes.
17. The method of claim 13 , wherein the predetermined threshold is selected such that the collective power of the spectral bins following excision is sufficiently low to maintain linear operation.
18. The method of claim 12 , comprising repositioning the antenna to place the directional interference within a null between a main beam and a sidelobe of the main beam.
19. The method of claim 12 , further comprising:
based upon the measures being below a threshold, tracking the desired signal in a closed loop;
based upon the measures exceeding the threshold, cease tracking the desired signal; and
after repositioning the antenna away from the directional interference, resume tracking the desired signal in a closed loop so as to sufficiently maintain power of the desired signal received by the antenna while sufficiently reducing power of the directional interference received by the antenna.
20. The method of claim 12 , wherein the desired signal further includes a signal identifier, the method further comprising:
generating a second correlation between the signal identifier and the sum beam; and
generating third and fourth correlations respectively between the signal identifier and the first and second difference beams,
wherein the antenna further is repositioned away from the directional interference based on the second, third, and fourth correlations.
21. The method of claim 20 , wherein the signal identifier comprises a pseudorandom code added to the desired signal.
22. The method of claim 20 , wherein the signal identifier comprises an existing feature of the desired signal wherein the existing feature is a frame format, preamble, or other characteristics unique to the desired signal.
23. A method for repositioning a directional antenna that responds to a desired signal and directional interference, the antenna generating a sum beam and first and second difference beams, the method comprising:
determining respective powers of the sum beam and the first and second difference beams;
excising at least a portion of the directional interference from the sum beam and the first and second difference beams;
determining measures of the directional interference in the sum beam and the first and second difference beams;
generating a first correlation between the sum beam and the first and second difference beams;
based upon the excision sufficiently removing the directional interference, tracking the desired signal; and
based upon the excision insufficiently removing the directional interference, repositioning the antenna away from the directional interference based on the powers, the measures, and the first correlation.