Abstract: A multibeam antenna capable of communicating with a plurality of satellites on stationary orbits at the same time includes a single main reflector, and a plurality of primary radiators for radiating electromagnetic waves toward the main reflector. The main reflector is constituted by the same number of partial reflectors as the primary radiators, the partial reflectors being joined to each other. Each of the partial reflectors is defined by a part of a different one of paraboloids which are different in the position of focus from each other. The primary reflectors are located at the positions of individual focuses. A subreflector is disposed between the main reflector and the positions of focuses and made up of a plurality of curved portions and a single flat portion.

Abstract: A primary radiator is provided which can be used in an attenna to be mounted in an artificial satellite. In particular, the primary radiator is designed to prevent an electrical charge caused by charged particles in a space environment. In the conventional type of radiator, there typically has been no arrangement for preventing such electrical charge which may cause a short-circuited condition resulting in providing noise or communication difficulties. In order to prevent this electrical charging, a fine metallic conductor is passed from the central part of a sub-reflector through an axial central part where an influence for the electromagnetic field is minimal within the circular waveguide constituting the primary radiator. The conductor is then connected to ground in a DC form at a rectangular and circular converter of the primary radiator.

Abstract: An antenna system in which main and subreflectors are arranged in such a manner to suppress the generation of a cross-polarized component due to the antisymmetry of the reflectors. Thereby, the antenna system can provide a preferable cross-polarization characteristics even in the working frequency bands.

Abstract: An offset antenna having a reflector of a paraboloid of revolution and a side plate surrounding the periphery of the reflector, wherein a primary radiator is disposed within the cylindrical side plate.

Abstract: A reflector antenna with a dish-shaped main reflector (10), and a self-supporting feed (11) for the transmission or reception of polarized electromagnetic waves. The feed (11) consists of a tube (12) which is attached to the middle of the main reflector (10) and is terminated by a subreflector (13) so that an intermediate space (14) is formed between the subreflector and the end of the tube. The part of the tube that is nearest the intermediate space (14) contains a cylindrical waveguide (15), or is the waveguide itself, and has an approximately circular or quadradic cross-section. Externally, the intermediate space (14) is bonded by a circular, cylindrical surface (16) with the same diameter as the outer diameter of the tube (12) this being called the aperture surface.

Abstract: A combined solar concentrator and radiator assembly (10) is provided in a relatively lightweight and compact geometry adapted particularly for use in electrical power generation systems in space. The solar concentrator - radiator assembly comprises a solar reflector of the Cassegrain type having primary and secondary reflelctor surfaces (14) and (26) for concentrating incident solar ration upon a thermal powered generator unit (16). The primary reflector surface (14) is formed on one side of an array of interleaved panels (30) adapted for movement between a compact stowed profile to fit within the cargo bay of a transport vehicle, and an extended deployed configuration. The reverse sides of these panels define a space radiator of extended surface area connected to the generator unit (16) by heat transfer members such as heat pipes (34) for purposes of dissipating excess heat to the surrounding space environment.

Abstract: The antenna has a main reflector (1), a subreflector (4a, 4b, 5a, 5b), and a feed radiator (2) which are all rotationally symmetric about a common axis (10). In a section in the direction of this axis of symmetry (10), the subreflector has the shape of two curves meeting in the axis of symmetry. Seen from the feed radiator, these curves are concave. Each of the two curves has at least one step (6a, 6b) for matching the feed radiator to the transmitter or receiver.

Abstract: An omnidirectional antenna comprises a ring-shaped subreflector surrounding an omnidirectional feed and a ring-shaped main reflector for redirecting radiation from the subsidiary reflector to the target zone. The feed has a focal ring and a hollow centre to accommodate supports, feeders etc which facilitates stacking of antennas.

Abstract: Two reflecting surfaces (102, 104) pass through each other at an intersection line (450) lying in a plane of symmetry (106). The two surfaces share a common aperture (101) and the surface contours of the two surfaces are preferably mirror images of each other and are arranged such that the respective two foci (110, 120) of the two surfaces are equidistant (108) from the center of the shared aperture and offset from each other in equal and opposite directions (109a, 109b) from the plane of symmetry.

Abstract: An antenna pointing device capable of scanning in two orthogonal directions comprises a fixed source (20) emitting a radio beam (21) and associated with a main offset reflector (10) and a secondary offset reflector (11), together with a set of at least three mirrors (14, 15, and 17) including a first mirror (14) aligned with the secondary reflector (11), and in which the second and third mirrors (15 and 17) are fixed to respective rotary drive mechanisms (16 and 18) for rotating them about two axes (.DELTA., .DELTA.') extending in orthogonal directions. The main and the secondary reflectors (10, 11) and the first and the second mirrors (14, 15) are mechanically fixed to one another in order to constitute a moving assembly. The second mechanism (18) drives both the third mirror (17) and said moving assembly (10, 11, 14, and 15).

Abstract: A multi-reflector antenna is disclosed which is arranged so that a main reflector surface, a subreflector surface and a primary radiator are electro-magnetically coupled together. When the main reflector is represented by a coordinate z=z(.rho., .psi.) using cylindrical coordinate system (z, .rho., .psi.) in which the direction of radiation of a main beam of the main reflector surface is in correspondence with the z-axis and the subreflector surface is represented by a coordinate r=r(.theta., .phi.) in a vector system using a spherical coordinate system (r, .theta., .phi.) in which the Snell's reference direction of the primary radiator is set to .theta.=0, the said z(.rho., .psi.) and r(.theta., .phi.) are so determined as to satisfy the law of reflection, a condition of constant path length and the following relation:.psi.=-.phi.+.psi..sub.0.rho.=.rho..sub.0 tan.theta./2where .psi..sub.0 and .rho..sub.0 are constants. The primary radiator is comprised of a plurality of horns.

Abstract: A satellite communications system employs separate subsystems for providing broadcast and point-to-point two-way communications using the same assigned frequency band. The broadcast and point-to-point subsystems employ an integrated satellite antenna system which uses a common reflector (12). The point-to-point subsystem achieves increased communication capacity through the reuse of the assigned frequency band over multiple, contiguous zones (32, 34, 36, 38) covering the area of the earth to be serviced. Small aperture terminals in the zones are serviced by a plurality of high gain downlink fan beams (29) steered in the east-west direction by frequency address. A special beam-forming network (98) provides in conjunction with an array antenna (20) the multiple zone frequency address function. The satellite (10) employs a filter interconnection matrix (90) for connecting earth terminals in different zones in a manner which permits multiple reuse of the entire band of assigned frequencies.

Abstract: The present invention relates to an antenna comprising a plurality of feeds, and either a single reflector or a single lens wherein the reflector or lens includes a predetermined curved major surface that produces a maximum field of view in a first one of two principal planes of the antenna. The major curved surface is designed to produce a first and a second "stigmatic" focal point, which are spaced apart by a predetermined amount on either side of an axis normal to the center of the reflector or lens in the first principal plane, such that the coefficient of astigmatism is at a maximum predetermined tolerable amount at the center and at the opposite edges of the maximum field of view to produce a peanut-shaped area where the coefficient of astigmatism is within tolerable limits.

Abstract: A shaped offset-fed dual reflector antenna having a main reflector, a sub-reflector and a primary radiator which do not block the wave-path of said main reflector is improved by using an inclined primary radiator from a boresight axis of the antenna, and the shaped non-quadratic surface in said main reflector and/or said sub-reflector, to provide the desired aperture field distribution, improved cross-polarization characteristics, and improved side-lobe characteristics. The incline angle of the primary radiator is in the range between 10 degrees and 40 degrees. When a gregorian antenna is used, and the aperture field distribution is Tailor's -40 dB distribution, said incline angle is preferably 16 degrees.

Abstract: An angular-diversity radiating system is described for tropospheric-scatter radio links which accomplishes a symmetrical Cassegrain optic in transmission and is parabolic with a central focus in reception, respectively. This is accomplished by a subreflector formed of parallel metal conductors and shaped with a hyperbolic profile which is centered on the axis of the main reflector at a predetermined distance between the transmitting horn and the receiving horns. The electromagnetic waves leaving the transmitting horn and directed toward the subreflector are polarized with the electric field vector parallel to the metal conductors of the subreflector such as to be reflected toward the main reflector which reradiates them. The electromagnetic waves received are polarized orthogonally to the transmitted waves and thus pass undisturbed through the subreflector to reach the receiving horns.

Abstract: A dual reflector antenna having two reflectors concave to each other and specially shaped so that beams incident on the antenna from two directions are reflected therefrom in collimated beams in two other directions.

Abstract: A space fed antenna system is adapted to correct for beam pointing (squint) errors and collimation errors caused by frequency variations of the R.F. energy radiated by the antenna system. A subarray of radiating elements is spatially positioned between an electronic lens and the focal point of said lens. The subarray radiates R.F. energy with a spherical wavefront for illuminating the electronic lens, such spherical wavefront having a focal point coincident with the focal point of the electronic lens. A programmer is provided which controls the electronic lens to collimate and direct the R.F. energy from the subarray. A corporate feed is provided which couples to a plurality of phase shifters which feeds corresponding time delay units, which in turn feeds corresponding radiating elements in the subarray. The phase shifters, responsive to the programmer, provide the spherical wavefront to the R.F. energy radiated by radiating elements in the subarray.

Abstract: A holographic aircraft antenna and method of fabricating the antenna are disclosed herein. The antenna includes a thin layer of dielectric strips of material contoured to and mounted on the conductive skin of the aircraft or a plurality of thin metal conducting strips secured to the skin of a composite aircraft. The spacing, width and size of the thin strips forms a hologram which is determined by the interference pattern of radio frequency beams selected for and directed at a holographic recording medium at particular angles to provide a desired or series of desired radiation patterns. In addition, a radar reduction device is provided wherein the hologram includes thin strips of dielectric material on the conductive skin of the aircraft or thin metal conducting strips on the composite aircraft.

Abstract: The present invention relates to a high-power solid state amplifier arrangement comprising a large number of solid state amplifiers disposed in a waveguide array. The waveguide array is disposed in the aperture of an antenna feed arrangement at the image plane of an antenna feed to receive a uniform distribution over the array with substantially no spillover. Each of the large number of parallel waveguide sections of the array includes one or more solid state amplifiers in a serial, waveguide-interconnected, arrangement, and a wideband impedance matching arrangement in the waveguide configuration at the input and output of the section.

Abstract: A reflector antenna system with reduced blockage effects is provided by placing a compensating reflector between the surface of the main curved reflector and its primary feed to intercept illuminating radiation which would otherwise be blocked by the feed. The compensating reflector reflects the intercepted radiation with a beam pattern which is essentially identical to the substractive blockage pattern. The compensating reflector is spaced from the main reflecting surface to place its beam pattern in phase opposition to the blockage pattern to cancel common components from the blockage pattern.

Abstract: The isolation of mainbeam and sidelobe jamming signals from the desired signal being relayed by microwave communication links is accomplished by an antijamming antenna comprising a flat radome, a curved reflector and a transmit dipole. Positioned adjacent the dipole is a monopulse feed and comparator for main-beam jammers (dual-plane monopulse, multi-mode multilayer feed). Also forming part of the integrated antenna are auxiliary units for near-sidelobe and far-sidelobe jammers. An alternative embodiment includes a Cassegrain grating sub-reflector. Since the direction of the desired incoming signal in microwave communication links is precisely known, the antijamming antenna uses azimuth and elevation monopulse to make a spatial distinction between the desired incoming signal and the jamming signals.

Abstract: An antenna system which has omnidirectional coverage in azimuth and sectoral coverage in elevation. A main reflector including a reflecting surface has polar symmetry about the Z-axis. It also has a cross section in any plane containing the Z-axis which satisfies the laws of power conservation and reflection. It is determined by the desired far-field pattern and the microwave feed pattern (for example TM.sub.01) employed. Single or dual reflector systems are described. Using the system on "receive" with multiple "feeds", full azimuthal direction finding of incident radiation can be achieved.

Abstract: An antenna having two crossed cylindro-parabolic reflectors in which the generatrices of said reflectors are orthogonal. The source is placed close to the center of the main reflector, which is further provided with polarization rotation means. The auxiliary reflector is placed facing the main reflector and it is such that it is transparent to a wave polarized linearly in one direction and reflecting to the waves polarized in an orthogonal direction.

Abstract: The present invention relates to an antenna arrangement for correcting for astigmatism is a beam which is linearly scannable in a first principal plane of the antenna arrangement. The antenna arrangement comprises a parabolic or torus main reflector and a feed arrangement for producing first and second astigmatic phase centers which lie along first and second focal lines, respectively, in the first principal plane and match first and second astigmatic phase centers required by the main reflector to produce a linearly scannable plane wave.

Abstract: A microwave antenna comprising the combination of a paraboloidal main reflector; a subreflector located such that the paraboloidal main reflector and the subreflector have a common focal point lying between the main reflector and the subreflector; a feed horn for transmitting microwave radiation (preferably symmetrically) to, and receiving microwave radiation from, said subreflector; and a shield connected to the peripheral portion of the subreflector and having an absorbing surface which reduces side lobe levels both by capturing the feed horn spillover energy and by reducing the diffraction of microwave radiation from the edge of the subreflector. The shield is preferably formed as a continuous axial projection extending from the periphery of the subreflector toward the main reflector substantially parallel to the axis of the feed horn. The reflective surface of the subreflector is suitably a section of an approximate ellipse.

Abstract: A dual gridded antenna reflector system and method for constructing the same is disclosed. The reflector system comprises a pair of reflector dishes each having a grid of parallel conductors. One of the reflector dishes is mounted over the other reflector dish by linear support ribs therebetween such that the conductors of the one reflector dish are perpendicular to the conductor of the other reflector dish. The linear support ribs are placed perpendicular to or parallel to the conductors of the overlapped reflector and are placed substantially outside of the high field region across the aperture of the overlapped reflector.

Abstract: The present invention relates to a scanning beam antenna comprising a doubly-curved main reflector, a doubly-curved subreflector and at least one linear array feed. The main reflector is doubly-curved in two planes to produce a separate first focus for each feed in a first plane in front of the subreflector and a separate second focus for each feed in a second orthogonal plane behind the subreflector. The subreflector is curved to refocus each second focus of the main reflector to coincide with the image line of a first axis on the reflecting surface of the main reflector in the first plane. Each feed array is disposed at a separate secondary focus of the combination of the main reflector and subreflector. The resulting antenna provides very little phase error due to aberrations as each beam is linearly scanned.

Abstract: An antenna system in which primary radiators are disposed on the radiation side of beams from a main reflector and in opposition to a subreflector and in which the subreflector and the primary radiators are disposed in positions offset from beam blocking positions.

Abstract: A portable, lightweight, folding parabolic reflector antenna for reception of microwave signals includes an axial wave guide tube which constitutes the main structural supporting member of the antenna, a ten to fifteen foot diameter dish mounted to the wave guide and a sub-reflector supported at the forward end of the wave guide. A low noise amplifier may be mounted to the rear end of the wave guide for amplification of the received signals. The folding dish includes a pre-formed dished reflector of pliable material supported by a radial framework of normally straight resiliently flexible spokes of tapering cross section. The spokes are pivotable by a lever system between a folded axial position and a deployed radial position.

Abstract: The present invention relates to an antenna arrangement for reducing multipath fades. The antenna arrangement comprises a curved main reflector disposed confocally with one focal point of a subreflector, and a feed arrangement. The feed arrangement comprises at least a pair of feed horns and a selectively movable plate reflector disposed between the feed horns and the subreflector along a feed axis of the antenna arrangement. The feed horns are disposed adjacent each other with the aperture of each of two feed horns covering one-half of the image of the main reflector. By selectively orienting the plate reflector so that one of the two multipath beams arrives with its central ray disposed orthogonal to the aperture of the feed horns, the contribution from each half of this beam received at each feed horn, for a particular frequency band, is equal and can be subtracted from the other half beam signal to cancel its effect without the need for an equalizer.

Abstract: The present invention relates to an antenna arrangement which includes a polarization diplexer capable of bidirectionally directing two orthogonally polarized signals along one path in the far field of the antenna arrangement and along two separate paths in the near field for interception along at least one of the paths by an array of feed elements. The array is arranged to provide a fixed linear phase taper along one axis across the array to produce or intercept a beam squinted at an angle 90 degrees-.alpha. to the face of the array and including a signal polarized in a first direction. Phase shifting means selectively produce a linear phase taper along a second axis across the face of the array orthogonal to the first axis to cause the beam to traverse a predetermined arc in the far field of view.

Abstract: This invention relates to a multi-beam antenna and a method of configuring the same, where the antenna consists of a main reflector, a plurality of horns for exciting the main reflector, and separate sub-reflectors for correcting phase errors of respective beams caused by reflection at the main reflector, or an integrated sub-reflector which is substituted for said separated sub-reflectors.

Abstract: A polarizer reflector includes a reflecting layer backing a meander-line polarizer effective to convert the incident beam from linear polarization to circular polarization during the propagation of the beam forwardly through the polarizer, and to reconvert the beam reflected from the reflecting layer from circular polarization to linear polarization but rotated at a predetermined angle, preferably at a right angle, with respect to the polarization of the incident beam. Also described is a reflecting plate-type scanning antenna including a front collimating paraboloid reflector with the above-described polarizer reflector serving as the back reflector, which arrangement has been found to substantially increase the frequency range of the scanning antenna.

Abstract: A frequency conversion interface is disposed between the main and subreflectors in a multiple beam antenna system so that the antenna system amplification factor will be defined by m=(f.sub.1 /f.sub.2).multidot.(.omega..sub.1 /.omega..sub.2), to permit large main reflector to subreflector area ratios while maintaining small amplification factors.

Abstract: This invention relates to a multi-beam antenna and a method of configuring the same, where the antenna consists of a main reflector, a plurality of horns for exciting the main reflector, and separate sub-reflectors for correcting phase errors of respective beams caused by reflection at the main reflector, or an integrated sub-reflector which is substituted for said separated sub-reflectors.

Abstract: A two reflector microwave antenna has a concave focusing main dish having an integral peripheral flange. An integral radome shell also having a peripheral flange is disposed in confronting relationship to the main dish flange. Mounted over both flanges is a clamping ring to keep the main dish and radome shell in a stress condition of fixed edge shells. A secondary reflector is provided on a central portion of the radome. The concave focusing main dish in one example, defines a paraboloid of revolution. Specific shapes of the main dish and the radome shell are selected to appropriately focus the microwave radiation. A radome portion of a variable thickness of dielectric material of the integral radome shell modify the path of microwave energy compensating for diffraction of induced edge spillover. The stress condition of the shells as maintained by the clamp about the flanges provides a structually rigid antenna substantially void of structural elements.

Abstract: A passive duplexer for electromagnetic waves operated within the millimetric wave range. The duplexer comprises a first horn associated with a radar transmitter and having a propagation axis (.DELTA..sub.1), a plane circular grid inclined at 45.degree. with respect to (.DELTA..sub.1), and a second horn associated with the radar receiver and having an axis (.DELTA..sub.2) at right angles to (.DELTA..sub.1). The grid is formed by a network of resonant slots equipped with at least one diode.

Abstract: A beam scanning antenna system that uses a small, rapidly rotatable feed enna to illuminate a large, fixed secondary collimating device, such as a reflector or electromagnetic lens, which in turn illuminates a large, fixed primary collimating device. The primary collimating device forms a narrow collimating beam that is reflected or transmitted into space. Rotation of the small feed antenna causes the beam to scan.

Abstract: A radar antenna with a collector of microwave energy incident along the main lobe of its radiation pattern, feeding a processor whose principal channel generates a raw output signal, is provided within the effective area of that collector with one or more ancillary radiation receivers intercepting energy from side lobes encumbered by interfering signals from directional jammers. The output signals of auxiliary channels connected to the ancillary radiation receivers are subtracted in the processor, at an intermediate-frequency level, from the raw output signal of the principal channel to produce a useful signal which is fed back to an adaptive cancellation loop in each of these auxiliary channels.

Abstract: A system for providing a far field shell-like conic pattern utilizing four quadrant oriented reflective optical assemblies. The pattern from each assembly covers one quadrant sector of the pattern and provides a shell having a thickness on the order of one degree.

Abstract: The invention relates to multi-mission orbital spacecraft of the kind comprising a platform and several different payloads including several telecommunication antenna feed systems.The problem is to avoid antenna interference, obtain bigger effective antenna aperture, avoid the necessity for replacing main antennae when replacing payloads, and make maximum use of longer platofrm life.In accordance with the invention, the antenna system comprises a common primary reflector which is a permanent integral part of the platform while the feed systems are mounted on the payloads, which may be launched separately, and are assembled with the platform to cooperate with the common platform antenna system in operation.The invention is mainly applicable to multi-mission satellites.

Abstract: A multifrequency antenna includes a main reflector for signals in a low frequency band. One or more portions of the main reflector are deformed to provide one or more auxiliary reflectors for signals in one or more higher frequency bands. The feed for the low frequency band is located axially of the main reflector, while the feeds for the higher frequency bands are offset to the side of the low frequency feed. The lateral and axial offsets of the vertex of an auxiliary high frequency reflector from the vertex of the main low frequency reflector and the focal length of the auxiliary high frequency reflector are selected to minimize the degradation of the performance in the low frequency band.

Abstract: An improved target seeker used in a pointer and tracking assembly for searching a large area in an X-Y plane, commonly called a field of regard. The improved seeker can search the field of regard using sweeps, spirals, circles and other types of scan patterns without blind spot restrictions.

Abstract: A short-focus microwave reflector is located a short distance away from the feed horn and is positioned to reflect the beam of microwave radiation away from the feed axis and toward a large primary reflector antenna for transmission. A conical shield extends from the feed horn to the secondary reflector, joining them together as a unit and preventing sidelobe radiation. The beam of radiation emerges from the shield through an aperture in the sidewall thereof. The short focus of the secondary reflector causes the beam to be focussed approximately at the plane of the aperture, such that the beam diameter is small and the aperture can also be small, reducing stray radiation from the shield structure. Diffraction at the edges of the aperture is reduced by a radially surrounding choke structure which further suppresses sidelobe radiation.

Abstract: The present invention relates to an antenna arrangement comprising a feed producing a predetermined feed aperture illumination and a plurality of sequentially arranged reflectors including a main reflector forming the aperture of the antenna arrangement. The present antenna arrangement also includes filtering means centered on a real focal point between two reflectors of the antenna arrangement. The filtering means is arranged to pass therethrough the central ray of a beam launched by the feed and for smoothing out discontinuities of the image of the feed aperture illumination in the area of the main reflector normally found without filtering. The main reflector is then made slightly oversize to intercept the smoothened-out image of the feed aperture illumination along a line which produces a predetermined level of edge intensity.

Abstract: A beam waveguide feeder in which a feed horn, a pair of revolvable paraboloidal reflectors, and at least one plane reflector are arranged in the order stated so as to form a path for an electric wave, said pair of paraboloidal reflectors facing each other and being equal in focal distance and off-set angle, their zeniths and focuses being on an identical plane, is characterized in that said feed horn can be fixed in position while its equivalent feed horn, i.e., the image of said feed horn focused by the beam waveguide feeder, can be moved into an arbitrary location and turned in an arbitrary direction.

Abstract: A mirror antenna employing a continuous mirror without a hole. A feed horn nd an electromagnetic lens, located behind a rotatable twist reflector (the mirror), collimates a beam toward a polarized reflector located near the twist reflector and tilted to aim energy toward the twist reflector. Energy reflected back toward the polarized reflector from the twist reflector passes through the polarized reflector to free space.

Abstract: The present invention relates to a multibeam antenna arrangement having minimal aberration of astigmatism and coma over a wide area of the focal surface of the antenna. The present antenna comprises a plurality of N reflectors arranged confocally in a sequence along a feed axis of the antenna and at least one feed disposed in the vicinity of a focal point on the focal surface. The reflectors and the at least one feed are further arranged to provide an equivalent centered antenna arrangement with the longitudinal axis of the feed corresponding to an equivalent axis of the centered arrangement for eliminating astigmatism. Coma is then eliminated by deforming two of the N reflectors in a predetermined manner.

Abstract: A reflector type radio frequency antenna having: a feed for producing a difference radiation pattern with a cone-shaped null region; and, a reflector having a surface disposed to reflect a portion of the energy in the difference radiation pattern and having the edge disposed in the cone-shaped null region. With such arrangement, since the edge of the reflector is disposed in the null region of the difference radiation pattern such edge is not radiated with energy which could otherwise illuminate such edge, scatter, and thereby generate unwanted side lobes in the free space antenna pattern.

Abstract: The present invention relates to an antenna arrangement which uses a large offset spherical main reflector to communicate with several, spaced-apart, remote locations. Large aberrations caused by the main reflector are corrected by a first subreflector forming a small image of the main reflector at a conjugate image surface and a second subreflector which is disposed at the image location and is shaped to correct for the aberrations caused by the main reflector. Such correction is, to a good approximation, frequency independent and provides aberration free operation at feeds adjacent each other and associated with remote locations having small differential angles of incidence on the center of the main reflector.