Communications: directive radio wave systems and devices (e.g. – Directive – Including a steerable array
Reexamination Certificate
1999-06-18
2001-06-12
Pihulic, Daniel T. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a steerable array
C342S374000
Reexamination Certificate
active
06246364
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to array antennas, and, in particular, to a lightweight modular low-level reconfigurable beamformer for array antennas.
2. Description of Related Art
Communications satellites are in widespread use. The communications satellites are used to deliver television and communications signals around the earth for public, private, and military uses.
The primary design constraints for communications satellites are antenna beam coverage and radiated Radio Frequency (RF) power. These two design constraints are typically thought of to be paramount in the satellite design because they determine which customers on the earth will be able to receive satellite communications service. Further, the satellite weight becomes a factor, because launch vehicles are limited as to how much weight can be placed into orbit.
Many satellites operate over fixed coverage regions and employ polarization techniques, e.g., horizontal and vertical polarized signals, to increase the number of signals that the satellite can transmit and receive. These polarization techniques use overlapping reflectors where the reflector surfaces are independently shaped to produce substantially congruent coverage regions for the polarized signals. This approach is limited because the coverage regions are fixed and cannot be changed on-orbit, and the cross-polarization isolation for wider coverage regions is limited to the point that many satellite signal transmission requirements cannot increase their coverage regions.
Many satellite systems would be more efficient if they contained antennas with high directivity of the antenna beam and had the ability to have the coverage region be electronically configured on-orbit to different desired beam patterns. These objectives are typically met using a phased array antenna system. However, phased array antennas carry with them the problems of large signal losses between the power amplifiers and the beam ports, because of the beamforming network interconnections and long transmission lines. Further, the beamforming network is heavy, difficult to integrate and test, and is difficult to repair or replace without large time and labor costs.
There is therefore a need in the art for a beamformer that can reduce the signal losses of a phased array antenna system. There is also a need in the art for a beamformer that is easier to integrate and test. There is also a need in the art for a beamformer that to provide more complete utilization of space assets without dramatically increasing the cost of manufacturing and operating a satellite.
SUMMARY OF THE INVENTION
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a method and apparatus for forming beams with antenna arrays. The modularity of the present invention is achieved by dividing the large array into a discrete number of smaller subarrays or panels. The beamforming network (BFN) is simplified by splitting the BFN into a primary dividing network and a secondary dividing network. Each beam has an independent beamforming network, the number of BFNs being equal to the number of beams.
A beamforming network in accordance with the present invention comprises an array of antennas and primary and secondary dividing networks. The array of antennas comprises at least a first subarray having a first number of elements and a second subarray having a second number of elements. The primary dividing network divides a beam signal into a plurality of panel signals, wherein a number of panel signals is substantially equal to a number of subarrays. The secondary dividing network divides a first panel signal into a first plurality of element signals substantially equal in number to the first number of elements and for dividing a second panel signal into a second plurality of element signals substantially equal in number to the second number of elements.
An object of the present invention is to provide a modular beamformer that can reduce the power dissipation and signal losses of a phased array antenna system. Another object of the present invention is to provide a beamformer that is easier to integrate and test. Another object of the present invention is to provide a beamformer that provides more complete utilization of space assets without dramatically increasing the cost of manufacturing and operating a satellite.
REFERENCES:
patent: 4814775 (1989-03-01), Raab et al.
Gulick Jon J.
Rao Sudhakar K.
Wu Shih-Chang
Gates & Cooper LLP
Hughes Electronics Corporation
Pihulic Daniel T.
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