Abstract: An array antenna is provided wherein each adjacent pair of a plurality of antenna elements in such array antenna have a common, conductive wall having a castellated radiating edge. Radio frequency energy resistive material is disposed within slots formed in the radiating edge. With such arrangement, electrical coupling between the adjacent pair of antenna elements is reduced thereby improving the gain of the antenna at the lower frequency operating band of the antenna. Further, the electric field distribution is redistributed by the slotted radiating edge from a cosine distribution associated with a linear edge to a more flattened, uniform distribution to increase the effective aperture of the element in the H-plane.

Abstract: A radio frequency antenna is provided comprising: a waveguide section; first means for establishing radio frequency energy in such waveguide section having a first linear polarization with an electric field disposed normal to opposing wide walls of the waveguide section; a planar microwave circuit means, for establishing a second linear polarization having an electric field disposed perpendicular to the electric field of the first linear polarization, such microwave circuit means being disposed within the waveguide between the wide walls and relative to the feed means to provide the first linear polarization and the second linear polarization with substantially coincident phase centers. In a preferred embodiment of the invention, the microwave circuit means includes a strip conductor feed separated from a ground plane conductor by a dielectric, such ground plane conductor having a notch formed therein and fed by the strip conductor.

Abstract: A radio frequency antenna element is provided comprising a waveguide having disposed within and adjacent to a rearward portion of such waveguide a ridge, such ridge having a relatively narrow forward portion and a plurality of feeds, disposed within the waveguide, for coupling energy from a plurality of sources to a relatively wider, rearward portion of the ridge. The waveguide has a pair of opposing, relatively wide upper and lower walls and a pair of opposing, relatively narrow side walls. The relatively wider, rearward portion of the ridge tapers to the narrower forward portion of the ridge in a plane parallel to the upper and lower walls of the waveguide. The narrow portion of the ridge tapers towards one of the wider walls as such ridge extends from the rearward portion of the waveguide to the forward portion of the waveguide.

Abstract: A radio frequency antenna comprising a waveguide having opposing relatively wide, upper and lower wall portions, a pair of opposing, relatively narrow side wall portions, and a relatively narrow rear wall portion, such portions being connected to provide a cavity having an open end disposed opposite the rear wall portion, the separation between the side wall portions decreasing as such side wall portions extend towards the rear wall portion. The waveguide includes a ridge disposed within the cavity, the decreasingly separated side wall portions of the waveguide being disposed between the ridge and the rear wall portion of the waveguide. The ridge is coupled to a coaxial transmission line. With such arrangement the decreasingly separated side wall portions of the waveguide improve the impedance matching between the coaxial transmission line and the ridged waveguide antenna element, thereby increasing the operating bandwidth of the ridged waveguide antenna element.