System and method for determining the beam center location of an antenna

#Embodiments of the present invention are generally directed to methods and systems for evaluating an antenna and, more particularly, to methods and systems for determining the beam center location of an antenna.

#An antenna or an antenna array (hereinafter collectively referenced as an “antenna”) shapes (by-design) radiated electromagnetic energy in specific patterns called beams. As such, the location of the center of the beam of an antenna also defines its pointing direction. For navigation satellites, it is useful to be able to point the beam of the navigation payload antenna to a specific location with increased precision as a jamming countermeasure, while for communications satellites, knowledge of the beam center permits communications to be conducted more efficiently. For example, more accurate pointing of the beam center of an antenna can facilitate communications at a lower power level or with improved throughput in comparison to communications conducted with an antenna having a beam center that is pointed with less precision.

#The beam center of an antenna may be controlled by mechanically moving the antenna to point in a desired direction. Alternatively, in antenna arrays, the beam center may be controlled by appropriately commanding attenuators and phase shifters to alter the amplitude and phase, respectively, of the signals emitted by the different array elements. Although the beam center of an antenna can be altered, the ability with which the beam center of an antenna can be pointed in a desired direction depends upon the accuracy with which the current beam center may be determined. Additionally, the beam center of an antenna will generally vary with temperature due to, for example, thermal deformations of reflectors or feeds and/or the temperature stability of phase shifters, attenuators or the like. As such, even if the beam center of an antenna is appropriate at one point, the beam center of the antenna may change as the temperature changes such that by monitoring the current beam center of the antenna, the antenna can be appropriately repositioned to maintain its operational efficiency.

#Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

#FIG. 1 is a perspective view of a GPS antenna;

#FIG. 2 is a schematic representation of the integrated transfer system (ITS) antenna elements and the L-band antenna elements of a GPS antenna; and

#The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

#Referring now to FIG. 1, a Global Positioning System (GPS) antenna 10 is depicted. The GPS antenna includes a plurality of L-band antenna elements 12 disposed in a central or interior portion of the antenna for transmitting signals having frequencies in the L-band. The GPS antenna also includes a plurality of integrated transfer systems (ITS) antenna elements 14 that are generally positioned about and, therefore, surround the L-band elements. The ITS antenna elements may be used for crosslink purposes, such as to permit communications between two or more antennas, such as the antennas onboard two or more space vehicles, e.g., satellites. Typically the ITS antenna elements support communication in a different frequency band than the L-band antenna elements, such as in the ultra high frequency (UHF) band. Although not described herein, the GPS antenna can also include a number of other antenna elements including a tracking, telemetry and command (TT&C) antenna element 16 having a generally cylindrical bicone antenna 16a and a conical spiral antenna 16b positioned upon the bicone antenna. While the ITS antenna elements are typically positioned symmetrically about the L-band antenna elements, the TT&C antenna element is generally positioned in a non-symmetrical arrangement and, in the illustrated embodiment, is positioned alongside the L-band antenna elements.

#While embodiments of the present invention will be described in conjunction with a GPS antenna 10 utilized for navigation purposes, the system and method of embodiments of the present invention can be employed in conjunction with a wide variety of other types of antennas, be it for navigation purposes, communication purposes or otherwise. Additionally, the system and method of embodiments of the present invention can be employed in conjunction with a single antenna as well as an array of antennas, such as the plurality of L-band antenna elements depicted in FIG. 1. As used herein, both a single antenna and an array of antennas will be referenced as an “antenna”.