Abstract: The present invention relates to a multibeam antenna arrangement comprising a main focusing reflector, a doubly curved subreflector disposed confocally with the main reflector and a plurality of feeds disposed on a doubly curved focal surface of the antenna on which an image of the far field of view is formed. The subreflector is doubly curved in orthogonal directions to introduce a predetermined amount of barrel distortion for transforming a three-dimensional, non-rectangular, matrix in the far field of the antenna arrangement into a substantially rectangular matrix on the doubly curved focal surface of the antenna arrangement. Feeds are aimed such that a central ray from each feed reflected by the subreflector impinges a common point on the main reflector.

Abstract: The present invention relates to an antenna arrangement for suppressing selected sidelobes where the arrangement comprises a main focusing reflector (10), a main feed arrangement (14) and at least two auxiliary feed arrangements (20 and 21) disposed on opposite sides of, and a predetermined equal distance from, the main feed arrangement in the plane of the sidelobes to be suppressed. All feed arrangements radiate the same signal and their individual beams are radiated in a direction whereby the central ray thereof impinge the same point on the main reflector. By proper adjustment of the phase, amplitude and transverse off-axis distance of the auxiliary feed arrangements from the main feed arrangement, the combined E-field distribution of the auxiliary feed arrangements at the edge of the reflector in the plane of the sidelobes to be suppressed will be equal and opposite to the E-field distribution of the main feed arrangement.

Abstract: The present invention relates to a wide-field-of-view antenna arrangement which permits the angular range over which multiple beams may be transmitted or received to be increased by taking into consideration the location of the tangential and sagittal focal regions associated with multibeam systems. The subreflector (18,24) is positioned relative to the main reflector (10,20) such that the tangential and sagittal focal regions lie behind the subreflector of a Cassegrainian arrangement, or alternatively in front of the subreflector of a Gregorian arrangement for a predetermined wide-field-of-view.

Abstract: The present invention relates to an antenna arrangement capable of correcting for astigmatism over a broadband range, the antenna arrangement comprising a main focusing reflector arrangement (10), such as, for example, a Cassegrainian antenna system, a feed arrangement (12) and an astigmatic correction means (14) disposed between the feed arrangement and the main focusing antenna arrangement. The astigmatic correction means comprises a first and a second doubly curved subreflector (18, 16) which are curved in orthogonal planes to permit the launching or reception of an astigmatic beam of constant size and shape over a broadband range. By proper choice of the angle of incidence at each subreflector, cross-polarization and astigmatism of the beam can be canceled simultaneously.

Abstract: An offset antenna and feed combination for use in a satellite communication system is disclosed wherein an array of adjacent microwave energy feed elements is disposed within a predetermined shape on the focal surface of the antenna for delivering electromagnetic energy to a remote, correspondingly shaped zone. Electromagnetic energy beams are selectively radiated towards predetermined areas of the overall remote zone by associated cluster groups of feed elements typically arranged as a minimum of one central and six surrounding feed elements. Additionally, each surrounding type of feed element of a cluster may be shared by two or more overlapping clusters, the overlapping clusters generating contiguous beams of electromagnetic energy in different frequency subbands.

Abstract: Microwave energy feed elements for launching essentially linearly polarized beams in a satellite communications system are oriented in the satellite's antenna so that the polarization directions of the feed elements form a rim and spoke configuration. The vertical polarizations are arranged to extend radially from a point on the antenna's focal surface which images the point on the surface of the celestial body directly below the satellite. Horizontal polarizations are arranged concentrically about the subsatellite image point. Electromagnetic energy launched from the feed elements will reach the surface of the earth at planes of incidence which are locally vertical and horizontal, thereby minimizing cross-polarization coupling between the orthogonally polarized signals due to such energy passing through precipitation.

Abstract: The present invention provides a polarization coupler which is capable of coupling or separating dual linear polarized microwave signals having frequencies which extend over extremely wide frequency bands. The present polarization coupler (11) comprises a main waveguide (12) and a side-arm waveguide (13) with a plurality of septa (16) arranged at the junction to reflect energy of a first polarization (E.sub.1) between the main and side-arm waveguide while energy of a second polarization (E.sub.2) passes the junction unaffected.