US Patent 7385560 Aircraft directional/omnidirectional antenna arrangement

A directional/omnidirectional antenna system is disclosed. A first printed circuit board has capacitive hats disposed thereon. Each capacitive hat is in association with one of an array of folded monopoles. A second printed circuit board has a switched beam forming network formed thereon. The switched beam forming network is configured to provide a predetermined omnidirectional antenna operation at a first switching position, and a predetermined directional antenna operation at a second switching position. Each of a plurality of feeding elements is associated with one of the folded monopoles. Each feeding element is coupled to one of the capacitive hats and to an antenna terminal. Shorting elements of the folded monopoles are coupled to the capacitive hats and to a ground plate of the antenna. A plurality of decoupling elements improve the antenna pattern for directional and omnidirectional modes and provide greater antenna gain.