Communications: radio wave antennas – Antennas – With means for moving directive antenna for scanning,...
Reexamination Certificate
2000-08-10
2001-11-13
Ho, Tan (Department: 2821)
Communications: radio wave antennas
Antennas
With means for moving directive antenna for scanning,...
C343S766000, C343S840000, C343S882000
Reexamination Certificate
active
06317093
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to communication systems, and more particularly, to satellite communication antenna systems.
BACKGROUND OF THE INVENTION
A satellite communication system generally includes an antenna that must be aligned with a geo-synchronous satellite. One such system, known as a Ku/Ka band system, generally transmits at the Ka band and receives at the Ku band. Typically, the antenna is coarsely pointed at the selected satellite after which an installation technician manually adjusts the antenna position by determining the peak Ku band signal by moving the antenna in azimuth and elevation. However, when the antenna is aligned with the satellite using the Ku band signal, the antenna may not be aligned with sufficient accuracy to achieve optimal Ka band transmission performance. This misalignment with the satellite can occur since the Ku bandwidth is much broader than the Ka bandwidth. In addition, changing atmospheric conditions can further impair a marginal alignment.
Typically, after aligning the antenna using the Ku band signal, the technician must contact a remote station to request an evaluation of the antenna's Ka band transmission characteristics. The alignment process continues in this way until the Ka band transmission is optimized to the extent possible using such a manual process. It will be appreciated that the foregoing is a time-consuming and expensive process.
It would, therefore, be desirable to provide a Ku/Ka band satellite communication system that automatically aligns an antenna with a geo-synchronous satellite with sufficient accuracy for optimal Ku band and Ka band performance.
SUMMARY OF THE INVENTION
The present invention provides an automated antenna alignment system that positions an antenna based upon a first signal with sufficient accuracy so as to optimize transmission of a second signal having a frequency higher than that of the first signal. This arrangement eliminates the need for a technician to manually position the antenna during the installation process. While the invention is primarily shown and described in conjunction with a dual reflector Ku/Ka band satellite communication antenna, it is understood that the antenna pointing system is applicable to a variety of antenna types having a range of sizes and transmit/receive frequencies.
In one embodiment, a Ku/Ka band satellite communication system includes an automated antenna alignment system that automatically aligns the antenna with a geo-synchronous satellite. The communication system includes a feed horn, as such term is understood in the art, aligned with the antenna, which can include a subreflector and a main reflector. A housing is coupled to a rear of the main antenna for containing azimuth and elevation drive assemblies. A control unit is secured to the antenna for controlling the drive assemblies that mechanically position the antenna system in azimuth and elevation, and for providing the azimuth and elevational positions to the controller. The control unit can further include a power meter for detecting signal strength from the feed horn and providing the signal strength information to a controller where the signal strength is correlated to the azimuth and elevational positions of the antenna.
In operation, the antenna is initially positioned such that a first signal having a first frequency is received by the antenna system. The system then effects a force on the antenna such that it is moved across a predetermined azimuth region while signal strength data is collected by the power meter and stored with the various antenna positions in the controller. Based upon the collected data, a signal peak location is selected, and the antenna is then repositioned at the position where the signal peak occurred. Signal strength data is then collected across a predetermined elevation region and a new signal peak location is chosen based upon the elevation data. This process is repeated a desired number of times to achieve a selected accuracy level.
The signal peak location can be determined using an algorithm, such as least squares parabola, on the collected azimuth and elevation data. Thus, the antenna is positioned with sufficient accuracy from the first signal to provide optimal signal transmission of a second signal having a bandwidth that can be significantly narrower than that of the first signal. The automated and accurate positioning of the antenna obviates the need for manual trial and error positioning of the antenna by a technician.
REFERENCES:
patent: 5089824 (1992-02-01), Uematsu et al.
patent: 5517204 (1996-05-01), Murakoshi et al.
patent: 5708679 (1998-01-01), Fernandes et al.
patent: 6043788 (2000-03-01), Seavey
Daly, Crowley & Mofford LLP
Ho Tan
Raytheon Company
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