Abstract: The present invention relates to hybrid mode feeds which are capable of handling very wide bandwidths. In the present feed arrangements, a dominant TE.sub.11 mode is converted to the HE.sub.11 hybrid mode which is then launched. The TE.sub.11 to HE.sub.11 mode conversion is achieved by inserting a circular dielectric rod (12) into a flared end (11) of a smooth-walled cylindrical feedhorn until a small cylindrical section of the dielectric rod engages with the inner wall (15) of the unflared portion of the feedhorn. In one feed arrangement, the other end of the dielectric rod is similarly inserted into a flared end (21) of a corrugated cylindrical feedhorn section (22) until a short longitudinal section of the cylindrical portion of the rod is concentric with the corrugations of an unflared section of the feedhorn to provide a transition for the HE.sub.11 mode into the corrugated waveguide for subsequent launch.

Abstract: The present invention relates to hybrid mode feeds which are capable of handling very wide bandwidths. In the present feed arrangements, a dominant TE.sub.11 mode is converted to the HE.sub.11 hybrid mode which is then launched. The TE.sub.11 to HE.sub.11 mode conversion is achieved by inserting a circular dielectric rod (12) into a flared end (11) of a smooth-walled cylindrical feedhorn until a small cylindrical section of the dielectric rod engages with the inner wall (15) of the unflared portion of the feedhorn. In one feed arrangement, the other end of the dielectric rod is similarly inserted into a flared end (21) of a corrugated cylindrical feedhorn section (22) until a short longitudinal section of the cylindrical portion of the rod is concentric with the corrugations of an unflared section of the feedhorn to provide a transition for the HE.sub.11 mode into the corrugated waveguide for subsequent launch.

Abstract: The present invention relates to a rectangular corrugated waveguide or feedhorn wherein a plurality of adjacent grooves of a predetermined depth and cross-section are formed, preferably by numerical machining, in a major exposed surface of each of four plates of an electrically conductive material. The four plates are then secured together to form a rectangular corrugated passage therebetween where the ends of the line of grooves in one plate substantially meet and are aligned with the ends of corresponding grooves in another plate to form a solid line of electrically conductive material at the corners of the passage.

Abstract: The present invention relates to an antenna arrangement which uses an imaging reflector (10) combined with a small feed or horn (14) which is capable of launching or receiving a spherical wavefront (18) to obtain a nearly frequency independent field distribution over a large antenna aperture. The antenna arrangement comprises a parabolic main reflector (10) disposed confocally with one focal point of a subreflector means (12) and a feed (14) disposed with the apex of the spherical wavefront at the other focal point of the subreflector means and the aperture of the feed centered on the image of the main reflector. If the rim of the feed aperture corresponds to an image of the edge of the main reflector, spill-over is substantially eliminated. Generally, any feed arrangement comprising a feed and subreflector means which transforms a spherical wavefront from the feed into a spherical wavefront emanating from the focal point of the parabolic main reflector can be used.

Abstract: The present invention relates to a method for reducing the grating lobes associated with phased array antenna arrangements. The present invention, which may be employed with any phased array antenna arrangement, consists of disposing a filtering means capable of blocking the grating lobes at any real focal point in the focal plane of the antenna arrangement. The size of the central region of the filter is determined by the desired field of view at the far-field, and may be adjusted so as to reduce the grating lobes to an admissible level with minimal gain degradation of the main beam.

Abstract: The present invention relates to an antenna arrangement capable of generating one or more linearly scanning spot beams which are scanned over separate strip portions of the entire field of view of the antenna. The antenna arrangement comprises an optical system comprising an aperture and a focal plane, and a novel feed arrangement. The feed arrangement comprises a separate linear phased array disposed within a separate rectangular waveguide section for each linear scanning beam desired. An offset curved reflector, disposed in each waveguide section, converts a linearly scanning planar wavefront generated by an array into a converging beam forming a linearly moving point source on the antenna's focal plane with the principle ray of each instantaneous wavefront being directed at the center of an image of the aperture of the optical system as seen by the feed arrangement.

Abstract: The present invention relates to antennas which have reflector arrangements that produce a large image with minimal aberrations at the exit aperture thereof of a small feed array. In the present arrangement, the feed array is placed at the conjugate plane relative to the exit aperture of a geometrically confocal reflector system comprising a parabolic main reflector and a parabolic subreflector so that exact imaging of the array is obtained at the exit aperture. In such arrangements, alignment and surface accuracy errors of the various reflectors can be easily corrected by appropriately changing the phase or the position of the associated elements of the feed array. A three-reflector arrangement having sequential geometric confocality is disclosed which also alters the focal length of the main reflector sufficiently to permit the inclusion of polarization and/or frequency diplexing means in the overall reflector system.

Abstract: The present invention relates to an antenna system for providing substantially perfect axial symmetry in the radiation pattern which combines (a) a curved main reflector, (b) at least two confocal subreflectors disposed to sequentially reflect a ray in either direction between the main reflector and a focal point of the antenna system as provided by the subreflector most distant along the feed axis from the main reflector, and (c) a symmetrical feedhorn disposed at the focal point of the antenna system so that its longitudinal axis coincides with the equivalent axis of the antenna system.

Abstract: The present invention relates to polarization grids for use in offset antenna arrangements, each of the grids comprising a plurality of nonparallel spaced-apart elements which are mounted between an offset curved focusing main reflector and an associated feedhorn in order to obtain linear polarization everywhere in the far field of the reflector. Exemplary types of grids in accordance with the present invention are (1) a family of hyperbolae on an arbitrary plane S, (2) projections of these hyperbolae on an arbitrary surface, and (3) a set of straight lines through a certain point F.sub.o.sup.' on plane S which set approximates the hyperbolae of type (1) by means of a tangent to each of the hyperbolae.