Importance

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Abstract

An antenna, such as may be employed for air-to-ground link hemispherical communication coverage, comprises a shaped ring focus type subreflector, that is rotationally symmetric about the boresight axis of a feed horn to which communication equipment on board an unmanned aerial vehicle is coupled. There is no main reflector associated with the shaped subreflector, so that rays from the subreflector, which emanate in a generally hemispherical pattern, are not intercepted. The generally hemispherical radiation pattern extends toward the horizon and encompasses a ground station. The subreflector is preferably shaped such that the hemispherical radiation pattern has a peak gain profile that extends from a first prescribed elevation differential slightly above the horizon to a second prescribed elevation differential slightly below the horizon. Although the feed horn causes a partial blockage of rays reflected by the shaped subreflector directly beneath the antenna, reduction in nadir gain is quite tolerable in a UAV application, as it lasts for only a fraction of second when the UAV platform passes directly over the ground station, where range-based propagation loss is minimum. Also, as the principal theater of deployment of a UAV is geographically remote from the ground station, nadir-associated gain reduction is not a practical problem.

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First Claim