Communications: directive radio wave systems and devices (e.g. – Directive – Including a steerable array
Reexamination Certificate
2000-04-07
2001-11-20
Phan, Dao (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a steerable array
C342S368000
Reexamination Certificate
active
06320538
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to antenna systems and, more specifically, to antenna systems that use phased array techniques.
BACKGROUND OF THE INVENTION
An electronically scanned reflector (ESR) is an antenna that uses a phased array feed to illuminate a nearby reflector unit to generate one or more steerable antenna beams. Such antennas are being used increasingly in space-based applications such as, for example, satellite communications applications. As can be appreciated, antennas implemented in such remote, unmanned space applications can be difficult to calibrate. That is, should the antenna undergo mechanical distortions in space that negatively effect its ability to generate desired antenna beams, it is often difficult to compensate for these distortions after they have occurred because the antenna is so far away. In the past, calibration of space-based phased array antennas was generally performed during lengthy procedures involving a multitude of ground station measurements that were complicated by orbit velocities, signal to noise, and antenna location uncertainties. Such procedures are very complex and expensive to implement and the results are sometimes inaccurate.
Therefore, there is a need for a method and apparatus for calibrating an electronically scanned reflector antenna that can be used in space based antenna applications. The method and apparatus should be capable of compensating for mechanical distortions to a space based antenna to a relatively high degree of accuracy without requiring remote antenna pattern measurements. In addition, the method and apparatus should be relatively easy to implement and operate.
SUMMARY OF THE INVENTION
The present invention relates to a method and apparatus for calibrating an electronically scanned reflector (ESR) antenna system. The method and apparatus are ideal for use with ESRs that are stationed in remote, unmanned locations, such as those implemented in space-based applications. The method and apparatus can also be used in connection with ESRs in any other environment. Displacement values are first generated for a plurality of points on the reflector and feed of the ESR antenna that describe how far the points are from their designed locations. The displacement values are then used to characterize the type of distortion within the reflector and the type of distortion within the feed. Based on the type of distortion found, compensation values are generated for each of the elements within the feed array for each beam position of the antenna. The compensation values are then used to assemble a lookup table for the antenna that can be used during normal antenna operation to achieve the desired beam positions of the antenna system.
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Kelly P. Keith
Lalezari Farzin
Ball Aerospace & Technologies Corp.
Phan Dao
Sheridan & Ross P.C.
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