Communications: directive radio wave systems and devices (e.g. – Directive – Including a steerable array
Reexamination Certificate
2002-11-07
2004-07-13
Blum, Theodore M. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a steerable array
Reexamination Certificate
active
06762718
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to beamformers for arrays of receiving or transmitting elements. More specifically, but without limitation thereto, the present invention relates to ground-based digital beamforming for stratospheric communications platforms.
In ground-based digital beam forming, the individual element signals of an antenna array on a stratospheric platform are linked with a ground station so that the beamforming calculations may be performed by hardware that is not subject to the power, size, and weight constraints of the stratospheric platform. In conventional digital beamforming methods, each element signal is multiplied by a different phasor corresponding to a selected beam, for example e
j&thgr;
i
, where &thgr;
i
is a phase angle calculated for each element i. The phasor products are then summed to form the selected beam. The phasors are selected so that signals arriving from a preferred direction add substantially coherently, while signals arriving from other directions add incoherently. The result is a spatial discrimination favoring signals arriving from the preferred direction and a corresponding enhancement of their signal-to-noise ratio. A problem with conventional digital beamformers is the requirement of a phasor multiplication for each element signal, typically N
2
for an N×N array. A reduction in the number of multiplications required would save processing time and resources that could be dedicated to other tasks.
SUMMARY OF THE INVENTION
The present invention advantageously addresses the needs above as well as other needs by providing a method and apparatus for beamforming signals for an array of receiving or transmitting elements.
In one embodiment, the present invention may characterized as a method for beamforming that includes the steps of selecting a beam elevation and azimuth and grouping elements of an antenna array into element ensembles that are substantially aligned with a wavefront projection on the antenna array corresponding to the selected beam elevation and azimuth.
In another embodiment, the present invention may characterized as a beamformer that includes a beam selector for selecting a desired beam elevation and azimuth and an ensemble selector for grouping elements of an antenna array into element ensembles that are substantially aligned with a wavefront projection on the antenna array corresponding to the selected beam elevation and azimuth.
The features and advantages summarized above in addition to other aspects of the present invention will become more apparent from the description, presented in conjunction with the following drawings.
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Chang Donald C. D.
Hagen Frank A.
Wang Weizheng
Yung Kar
Blum Theodore M.
Crook III John A.
Grunebach Georgann S.
The DirectTV Group, Inc.
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