Abstract: The present invention relates to a multibeam antenna arrangement having minimal primary 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 substantially parallel to an equivalent axis of the centered arrangement for eliminating astigmatism. Primary coma is then eliminated by deforming two of the N reflectors in a predetermined manner.

Abstract: The present invention relates to an antenna feed arrangement for correcting for astigmatism caused by an offset main reflector. The feed arrangement comprises at least one feed element, a first and a second cylindrical reflector disposed along the feed axis of the antenna with corresponding axes across the reflecting surfaces thereof oriented orthogonal to each other, and a pair of plates comprising a conductive material which are disposed parallel to, and on either side of, the feed axis of the antenna to enclose the area between the at least one feed element and the first reflector while forming an aperture thereof within a predetermined distance from the second reflector.

Abstract: The present invention relates to antennas with a segmented reflecting surface for providing fully or partially overlapping beams from separate feeds associated with each segment without incurring cross-coupling between feeds and power loss. More particularly, a main reflector or a subreflector reflecting surface is segmented to provide separate images of the far field area of the antenna on separate focal surfaces in the vicinity of an original focal surface of a corresponding non-segmented antenna. Feeds disposed at essentially corresponding locations on each of the far field area images produced by each of the segments provide separate beam footprints which overlap each other in the far field area by a predetermined amount.

Abstract: Directive antenna or radio telescope systems in which a large aperture objective directs incident electromagnetic energy onto a relatively much smaller field element which in turn directs it upon a small directive feed such as a phased array.

Abstract: An antenna having a frequency separator of the type comprising plural lattice structures of a periodic conductive pattern. Each lattice structure exhibits an inherent resonance frequency and an inductance-capacitance effect at frequencies below the inherent resonance frequency. The periodic conductive patterns are selected so that each of the lattice structures exhibits substantially the same inherent resonance frequency, and when placed at selected intervals, the plurality of lattice structures exhibit interactive resonance at frequencies below the inherent resonance frequencies. Each lattice also exhibits substantially equal inductance and capacitance with respect to obliquely incident electromagnetic waves in the TE and TM modes.

Abstract: A dual band mirror antenna employing a continuous mirror without a hole. e-by-side feeds for each band and an electromagnetic lens, located behind a rotatable twist reflector (the mirror), collimate beams toward a pair of polarized reflectors located near the twist reflector and tilted to aim the reflected energy toward the twist reflector. One polarized reflector is reflective at the higher radiofrequency band and transparent at the lower radiofrequency band. The other polarized reflector is reflective at both bands. Energy directed back toward the polarized reflectors from the twist reflector passes through the polarized reflectors to free space.

Abstract: A multiple reflector antenna is disclosed that comprises a main reflector formed of a portion of a rotatively symmetrical surface with respect to a rotation axis, a sub-reflector, at least one auxiliary reflector, and at least one wave source, said rotation axis being parallel to or slightly deviated from an aperture plane. This antenna is characterized by such construction that said sub-reflector and auxiliary reflector intentionally cause distortion of an electro-magnetic field distribution to cancel the distortion generated at said main reflector.

Abstract: The present invention relates to a phased array antenna system which transmits a local oscillator signal in a scanable spotbeam from a first array of feed elements (12.sub.l -12.sub.m) via a reflector or lens (16) and a frequency diplexing means (18) to a second array of feed elements (20.sub.l -20.sub.n) disposed on the image plane of the first array of feed elements. A message signal in a second beam also impinging the frequency diplexing means from a separate direction is also received at the second array of feed elements. The message signal and the local oscillator signal concurrently received at each of the feed elements of the second array are mixed in individual mixers and the output of each mixer can be reradiated for transmission to a remote receiver or combined with the outputs of the other mixers for use by a local receiver.

Abstract: The present invention relates to a feed arrangement for use with compact scanning beam antennas which comprises a linear phased array of small feed elements (10) which form an approximate line source that radiates a wedge-shaped cylindrical beam toward a subreflector (12) which is shaped to focus the wedge-shaped cylindrical beam to a point source which then produces a spherical wavefront. The spherical wavefront can then be focused by a main reflector (14) into linear scanning beams if desired. Multiple linear phased arrays of small feed elements can be disposed parallel to each other to form a multibeam feed arrangement for producing multiple fixed or scanning spot beams.

Abstract: A confocal parabolic antenna system includes a grid of parallel metallic strips placed in the focal plane of the antenna system. The strips are oriented in the direction of an uplink wave polarization and eliminate the grating lobes at the uplink frequency band by reflecting the energy of the particular spatial harmonic components which give rise to the grating lobes.

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 phased array antenna arrangements which comprise a linear array of feed elements where the array has an aperture which is out at a bias angle along the minor axis of the array to produce a fixed linear phase taper along the minor axis by all elements. Then by linearly scanning the array along the major axis of the aperture of the array, a beam is scanned along an arc which can be made to correspond to an orbital arc segment around a celestial body and within the field of view of the antenna arrangement when the bias angle is properly chosen. The feed elements can comprise long feedhorns or horn antenna configurations which can be used in a separate array or disposed in an array on a conjugate plane of a main cylindrical reflector when used in multiple reflector phased array antenna arrangements.

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 provides a bifocal reflector antenna with no aberration and a configuration process thereof wherein the two-dimensional Ray Lattice Method is extended to the three-dimensional method. By setting the central section curve of a subreflector or main reflector as an initial condition, the surface curves of the sub- and main reflectors are determined so that a ray from the focus to the antenna aperture can satisfy the reflection law and path length condition. The aberration over the antenna aperture is perfectly eliminated by using the new method.

Abstract: The present invention relates to the orientation of antennae on a satellite possessing at least one antenna comprising a horn rigidly connected to the body of the satellite, a movable reflector mounted on an orientable platform and at least one radio-frequency sensor in the horn using said antenna to control the orientation of said reflector. The invention consists of: using a signal characterizing the pivoting of the orientable platform with respect to the body of the satellite to orient said satellite correctly with respect to the reflector in order to limit the pivoting of said platform; using the signals from at least one earth sensor in the same way as the signals from the radio-frequency sensor to control said reflector, so as to orient the beam towards the point sighted on the earth. The invention is particularly useful for the control of the orientation of antennae, particularly on a satellite.

Abstract: The antenna system employs a parabolic reflector fed by an offset feed array of circular wave guides located substantially at the focus of the parabolic reflector, but offset from the axis thereof. A plurality of aperture tuning mechanisms disposed at the mouths of the circular waveguides of the waveguide feed array, and having physical lengths much shorter than one wavelength at the frequencies involved, are provided to reduce cross-polarization and mutual coupling between adjacent feeds. The short resonant length of these tuning mechanisms, and their shape which is chosen to generate the TM.sub.11 mode E-field contour line ensures that they are effective over a broad bandwidth of as much as 20% or more. Within this bandwidth, they act as inductive suppressors to control both cross-polarization and mutual coupling between adjacent feeds.

Abstract: An improved directional antenna for microwave transmissions is disclosed comprising a paraboloidal main reflector, a waveguide feed having a first open end thereof positioned on the axis of the main reflector, and a second waveguide of the same size serially connected between the second open end of the waveguide feed and a transmission device such as a microwave transceiver. The waveguide feed has an elliptical cross-section throughout its axial length, thus providing an elliptically shaped first open end that in of itself and without separate horn attachment, functions as a feed energizer; while the second waveguide also has an elliptical cross-section of the same size, which in combination with such waveguide feed provides a microwave coupling to the transmission device that minimizes reflections, respectively matching problems, especially in the case of overmoded waveguide applications.

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: 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 Cassegrain antenna system, a feed (12) and astigmatic correction means (14) disposed between the feed and the main focusing antenna arrangement. The astimatic correction means comprises a first and a second doubly curved subreflector (16, 18) or lens (30, 32) which are curved in orthogonal planes to permit the launching of an astigmatic beam of constant size and shape over a broadband range.

Abstract: An antenna system has a parabolic reflector mounted so that it points generally downwards and a primary aerial is located at the focus of that reflector. Waves from the primary aerial are reflected back by the parabolic reflector to a reflector plate through an aperture in which the primary aerial projects. Scanning in both elevation and azimuth is effected by movement of the reflector plate.

Abstract: A microwave antenna for use at a limited number of non-harmonically related frequencies, particularly two, includes a pair of reflectors, a detector diode, and a modulator diode mounted on a waveguide in operative spatial relationships which are compromises of closely occurring multiples of half or quarter wavelengths of the frequencies of interest. More particularly, the reflectors are spaced apart such a compromise distance which results in a low voltage standing wave ratio. The antenna includes a coaxial detector diode holder or sidearm positioned on the waveguide and in communication therewith at a position to provide sharp tuning at one of the frequencies while the detector diode is positioned in a coaxial diode holder at a location operative to sharply tune the other frequency. The modulator diode is positioned in the waveguide a distance from the detector diode holder which is a compromise distance based on in-guide half wavelengths at each of the frequencies.

Abstract: A reflection-type polarizer for modifying the polarization of an incident electromagnetic wave. The polarizer comprises a reflector positioned at a predetermined distance from a polarization filter constituted by a metal plate having a bi-dimensional periodic network of resonant slots at the operating frequency. The polarizer has application to microwave antenna systems and particularly to Cassegrain antennas.

Abstract: A parallel-plane antenna of the pillbox or cheese type in which the cylindrical-parabolic portion is constituted by a semitransparent reflector and the focal plane of which is constituted by a polarizing reflector. The cylindrical-parabolic semitransparent reflector is constituted by an array of wires parallel to the plane of polarization of the wave emitted by the source. The polarizing reflector is formed by a reflecting plate located at a distance of .lambda./4 from an array of parallel wires inclined at 45.degree. with respect to the plane of polarization of the incident wave.

Abstract: The present invention relates to a quasi-optical frequency diplexer capable of operating over a wide angle of scan and separating microwave signals possessing proximate center frequencies. The present invention, which in one aspect may be employed with a phased array antenna arrangement functioning so as to separate the transmit and receive frequencies associated therewith, consists of an array of waveguide sections (22) where the input and output ports (30, 32) of the array are tilted with respect to the array's longitudinal axis. The angles of tilt and the dimensions of the waveguide sections may be adjusted so as to achieve frequency diplexing with a minimal amount of interference between the diplexed signals.

Abstract: A microwave limb sounder (MLS) to measure trace gases in the upper atmosphere by comparing spectral noise content of limb soundings with the spectral noise content of cold space utilizes an offset Cassegrain antenna system and a tiltable input mirror to alternately look out at the limb and up at cold space at an elevation angle of about 22.degree.. The mirror can also be tilted to look at a black body calibration target. Reflection from the mirror is directed into a radiometer the head of which functions as a diplexer to combine the input radiation and a local oscillator (klystron) beam. The radiometer head is comprised of a Fabry-Perot resonator consisting of two Fabry-Perot cavities spaced a number of half wavelengths apart. Incoming radiation received on one side is reflected and rotated 90.degree. in polarization by the resonator so that it will be reflected by an input grid into a mixer, while the klystron beam received on the other side is also reflected and rotated 90.degree.

Abstract: A conical scan microwave antenna having a stationary fixed axially symmetric primary reflector consisting of any concave surface of revolution along with a spherical wave point source feed-and-subreflector assembly potentially rotatable about the axis of the primary reflector, and with the surface of the subreflecror being shaped so that the reflection of the spherical wave from the feed and off of the subreflector strikes the primary antenna and is reflected as a co-planar wavefront from every point on the primary reflector, and, further, the subreflector-and-feed assembly is located outside of the aperture of the reflected pencil beam such that for any given scan position of the subreflector, no portion of the reflected wavefront intersects the subreflector or its feed.

Abstract: An antenna designed to emit a beam of generally elliptical cross-section has a reflector with a parabolic-elliptical concave surface conforming to the formula(x/p)+(y/q)=2zwhere p and q are the parameters of its parabolic cross-section in the xz and yz planes, respectively. A microwave feed located on a line interconnecting the foci of these two parabolas, preferably at the outer focus separated from the surface vertex by a distance q/2, generates a beam parallel to the axis whose ellipticity depends on the ratio q/p.

Abstract: An antenna structure includes an at least partly parabolic main reflector and an auxiliary reflector of generally similar configuration, the two reflectors having confronting concave surfaces and lying respectively above and below a horizontal plane including a common focus of these surfaces. A corrugated horn illuminating the auxiliary reflector extends at the level of the latter, with a substantially horizontal axis, between vertical planes passing through the vertex of the parabolic main-reflector surface and through the common focus; in one embodiment, the horn forms with the auxiliary reflector a unitary assembly closed on all sides except for an upper aperture facing the main reflector.

Abstract: An antenna set-up comprising a first and a second reflector in the form of substantially parabolic cylinder surfaces and a feed source, directed to the first reflector and placed on the focal line of that reflector and in which set-up the directrix of the cylindrical wave front obtained by exposure of the first reflector coincides with the focal line of the second reflector and the focal line of the first reflector is not parallel to the symmetry plane of the second reflector.

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: A rear feed assembly for a microwave aerial, comprising a dielectric support member having an energy reflecting surface positioned against one face thereof. Waveguide means is connected with the support, the center of the waveguide aperture being the phase center of the assembly and the said face of the support being located in the far field region with respect to that center. The support is so shaped that energy emitted from the waveguide means is reflected from the reflecting surface and emerges through a second face of the support with a spherical wavefront centered on the image phase center.

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 novel launcher reflectors which are used with reflector antenna systems to compensate for the dominant aberration of astigmatism which was found to be introduced in the signals being radiated and/or received at the off-axis positions. A major portion of such phase error is corrected by using, with each off-axis feedhorn, an astigmatic launcher reflector having a curvature and orientation of its two orthogonal principal planes of curvature which are chosen in accordance with specific relationships, the launcher reflector being fed by a symmetrical feedhorn.

Abstract: An antenna for use in propagating or receiving microwave radiation having both left-hand and right-hand circular polarization. The left-hand and right-hand circularly polarized radiation may be transmitted or received simultaneously without interference with one another, that is, they are isolated from one another by 27 dB or more. The preferred antenna comprises an array of closely clustered waveguide elements each of which converts respective linearly polarized signals to left-hand and right-hand circularly polarized signals and vice versa. Isolation means also are provided in each of the waveguide elements for preventing radiation either propagated or received by a waveguide element from being coupled into the radiation being propagated or received by other waveguide elements in the array. Preferably, square waveguide is utilized for the array elements and the isolation is provided by a plurality of conductive elements mounted on each of the open ends of the waveguide elements.

Abstract: An antenna assembly wherein the direction of a beam of radio frequency energy may be changed by combining the effects of a mechanically movable reflector and an electromagnetic lens is disclosed. In the preferred embodiment the antenna arrangement includes a corporate monopulse feed arranged to produce a linearly polarized divergent beam which is first reflected from a linearly polarized paraboloid to direct a convergent beam toward a mechanically rotatable polarization-twisting reflector. A selected portion of a spherical electromagnetic lens arrangement is illuminated by the still convergent beam from the latter reflector, such lens then determining the direction of the beam finally propagated in free space.

Abstract: A directional microwave antenna system comprising a concave reflector fed by a wave guide and splash plate assembly. Two rectangular apertures in the wave guide at the focus of the reflector admit energy to and from the splash plate. Impedance matching tabs protrude into the rectangular apertures to match the antenna system. Rectangular tabs provide improved VSWR, high side-lobe reduction with the reflector on-axis. Circular tabs provide improved VSWR and good side-lobe reduction with the reflector on or off axis.

Abstract: The present invention relates to a scanning system comprising a three elet reflecting antenna, wherein two of the reflecting elements synchronously counter rotate about axes other than their optical axes in order to generate a linear scan.

Abstract: According to the present invention, radar rays are reflected off a rotating econdary reflector which is both tilted with respect to and synchronously translated, in simple harmonic motion, in a direction transverse to the axis of rotation of the secondary reflector. The combined effect of the tilting and translating of the secondary reflector is to produce a line scan when the rays from the secondary reflector are reflected off a primary reflector.

Abstract: An antenna for "frequency-re-use" that is provided with more than two parabolic cylinder surfaces (as reflectors), having in pairs common line foci, which foci intersect or cross each other, and having in pairs common symmetry planes.

Abstract: Omnidirectional antenna provided with a rotation-symmetrical reflector and a concentric radiator, to be mounted around a mast, which radiator has an uninterrupted annular exit edge. All the diametrical cross sections of the radiator along the axis of the antenna are uniform. The path followed by the radiation in the radiator beyond the part deflecting from the axis of the antenna, is turned up in the direction of the reflector.