Abstract: A unique feed structure for improving the cross-polarization performance of a reflector antenna system is disclosed. According to the present invention, the feed structure is an array including a number of feeds, which are rotated in a predetermined fashion to yield superior cross polarization performance of the antenna system. The array feed in the center of the feed structure is positioned approximately in the focus of the antenna reflector. The array feeds located on the y-axis are slightly rotated in either a clockwise or a counter-clockwise manner. The magnitude of the rotation is proportional to the distance of the feeds from the x-axis along the y-axis. The rotation of the feeds yields significant performance in cross polarization performance, while having little or no co-polarization effect.

Abstract: A Cassegrain antenna system includes a flat dielectric plate radome having a thickness of one-half wavelength at a frequency of operation. The plate has an electrically conductive grid disposed on an inside surface thereof to permit perpendicularly polarized energy rays to pass there-through. A parabolic twist reflector is spaced from the radome, and includes a dielectric substrate having a thickness equivalent to one-quarter wavelength at a frequency of operation and having formed on an interior surface thereof an array of conductive strips oriented by 45 degrees relative to the incident ray polarization. A conductive ground layer is formed on an exterior surface of the substrate, wherein radiation reflected by the ground layer and passing through the dielectric substrate is shifted by 180 degrees in phase and is rotated in polarization when combined with energy reflected from the conductive strip array by 90 degrees relative to radiation incident on the twist reflector.

Abstract: The invention consists of improvements of reflector antennas with self-supported feeds. The feed consists of a waveguide tube, a dielectric joint and a sub-reflector. The tube is attached to the center of the rotationally symmetric reflector and extends to the focal region of it. The sub-reflector is located in front of the tube, and the surface of this sub-reflector is provided with rotationally symmetric grooves also called corrugations.

Abstract: A dual-reflector microwave antenna comprises the combination of a paraboloidal main reflector having an axis; a waveguide and dual-mode feed horn extending along the axis of the main reflector, a subreflector for reflecting radiation from the feed horn onto the main reflector in the transmitting mode, and a shield extending from the outer edge of the main reflector and generally parallel to the axis of the main reflector, the inside surface of the shield being lined with absorptive material for absorbing undesired radiation. The subreflector is shaped to produce an aperture power distribution that is substantially confined to the region of the main reflector outside the shadow of the subreflector. The support for the subreflector is preferably a hollow dielectric cone having a resonant thickness to cause energy passing through said cone to be in phase with energy reflected off of said cone so as to achieve phase cancellation.

Abstract: An optical reflector antenna utilizes a subreflector that is offset from the optical axis of the antenna and that revolves about the optical axis to scan the beam from the antenna in a circular path about the axis of the antenna to facilitate the search for and acquisition of a satellite for subsequent tracking and communications. The subreflector is mounted on a rotatable shaft that is aligned with the optical axis of the antenna. When the shaft is not being rotated, one or more springs hold the subreflector in a fixed position aligned with the optical axis of the antenna to facilitate tracking and communications. When the shaft is rotated, rotational forces cause the subreflector to shift to and remain at a position that is offset from the optical axis and the rotation of the shaft causes the offset subreflector to revolve about the optical axis of the antenna, thus scanning the beam from the antenna to facilitate the search for and and the acquisition of the satellite.

Abstract: An antenna system includes a beam source of a microwave wave beam, a gimbaled antenna, and a waveguide including a mirror system that directs the microwave wave beam from the beam source to the antenna. The mirror system is formed of a series of mirrors operable to reflect the microwave wave beam and includes a first paraboloid mirror positioned to receive the microwave wave beam from the beam source, a first planar mirror positioned to receive the microwave wave beam from the first paraboloid mirror, a second paraboloid mirror positioned to receive the microwave wave beam from the first planar mirror, and a second planar mirror lying on the system azimuth axis and positioned to receive the microwave wave beam from the second paraboloid mirror. The first planar mirror may be controllably tilted to finely steer the aim of the microwave wave beam to the antenna.

Abstract: An improved very small antenna terminal (VSAT) dual-beam antenna system for use with user subscriber terminals that communicate with low-earth orbiting and other satellites. In one embodiment, the dual-beam antenna system has two offset Gregorian dual-reflector antennas that each has an ellipsoidal subreflector and a rotatable paraboloidal reflector having a focus in common with a focus of the ellipsoidal subreflector. The rotatable paraboloidal reflector couples energy to and from the ellipsoidal subreflector. An RF feed system couples RF energy to and from the ellipsoidal subreflector. Rotating apparatus rotates the paraboloidal reflector and ellipsoidal subreflector together around an azimuth axis of the antenna. The rotating apparatus independently and simultaneously rotates the paraboloidal reflector about an axis between the paraboloidal reflector and ellipsoidal subreflector which points the antenna at an orbiting satellite.

Abstract: The present invention provides a reflector antenna which has dual polarization with low cross polarization within the main lobe and side lobes of the radiation pattern. The antenna includes a dish-shaped main reflector with a center located, self-supporting tubular feed element and a sub-reflector mounted on the free end of the tube and located at the focal area of the main reflector. The tube and sub-reflector are separated by a space which can be open or filled with a dielectric material. The diameter of the sub-reflector is greater than the tube. The surface of the sub-reflector facing the main reflector includes one or more concentric circular corrugations which can be filled with a dielectric material.

Abstract: A wide band phased array antenna includes a radio frequency reflector hav a focal axis, and first and second sides and an m number of transverse electromagnetic transmission carriers, where each of the carriers includes a first conductor which generally transects the focal axis of the reflector and is electrically connected to a first side of the reflector, and a second conductor electrically connected to a second side of the reflector, where m is a positive integer. The RF reflector is located between the first and second conductors for guiding the beam.

Abstract: An improved reflector antenna with far improved return loss than prior art subreflector antennas is disclosed herein. The invention uses a circular waveguide antenna feed employing a non-planar, subreflector having a radial cavity which reflects the energy from the waveguide onto a rotationally symmetrical main reflector. The dimensions of the feed tube, the subflector, and the connection between them are chosen to make the total reflection back into the feed tube very close to zero. The dimensions of the antenna feed are also chosen such that its radiation pattern has an amplitude null along the antenna feed axis. This further improves return loss by minimizing the amount of energy from the main reflector that gets directed back into the feed tube. An alternate embodiment features a feed radiation pattern with an asymmetric amplitude taper for improvement of the sidelobe envelope in a preferred plane.

Abstract: An improved subreflector antenna with lower sidelobes than prior art subreflector antennas is disclosed herein. A tapered, anisotropic, corrugated subreflector is attached to a waveguide and located at the focus of a near-parabolic deep dish main reflector. The subreflector has corrugations of varying depth. The varying depths of the corrugations result in varying reactance, or reactance taper, of the subreflector. This taper is designed in such a manner to guide or steer the energy from the antenna feed to the main reflector in such a manner as to help assure sharply reduced sidelobes. Further, the subreflector is physically shaped so as to further steer or guide the energy in the desired direction. The deep geometry of the main reflector allows the reduced sized subreflector to be positioned within the rim of the main reflector such that the combination can be covered by a flat radome.

Abstract: The problem of reducing the size of a dual offset Cassegrain reflector type microwave antenna without adversely affecting performance while retaining the simplicity of the main reflector's (1) and subreflector's (3) traditional simple surface curvatures is solved by having the paraboloidal shaped main reflector's focal length, fm, and diameter, D, fulfil the criteria that the ratio of fm to D is less than 1.0; and in which the hyperboloidal shaped subreflector (3) is oriented so that its left foci, at which the microwave feed (5) aperture is placed, lies above the main reflector's focal axis. It's subreflector subtends an angular arc about the focal point that is slightly larger than the corresponding arc subtended by the main reflector. The elegance of the compact antenna is demonstrated by improved performance, attaining efficiencies in excess of seventy three percent.

Abstract: Radio waves from the point f2 of the horn 7 are reflected in the diagonal direction at the sub reflector 3 for transmitting and receiving the radio waves and then further reflected at the main reflector 5 so that a fan-shaped beam narrow in the lateral direction is designed to direct in the horizontal direction, and the main reflector 5, the sub reflector 3, and the horn 7 are built into an antenna proper which is designed to be rotatable around the vertial axis 8 passing the point f2 with the rotating means 23, 24, 25 so that the structure is simplified and manufacturing costs are reduced.

Abstract: A method for designing a shaped dual reflector antenna comprising the initial selection of a hyperboloidal or ellipsoidal reflective surface profile for the main reflector such that the cross-polarization of the contoured output RF signal beam of the resulting antenna structure is reduced.

Abstract: A device for damaging electronic equipment has a millimeter wave generator, such as a gyrotron oscillator, for producing very high power millimeter waves. A beam former antenna forms the millimeter waves into narrow beams for distance transmission. An antenna coupled to the gyrotron directs narrow beams of the millimeter waves to selected targets, whereby the beams damage electronic equipment at the targets. The millimeter wave generator produces frequencies ranging from about 100 to 140 GHz at 20 millisecond megawatt pulses at 400 kilowatts CW.

Abstract: A feed transport device for moving a feed within a non-planar focal surface defined by a satellite communications antenna, comprises first and second non-linear rails, and a feed transport unit comprising a feed support member for supporting the feed, and first and second slidable members slidably mounted on said first and second rails respectively to permit each slidable member to slide along the length of its respective rail, wherein one end of the feed support member is pivotally attached, not necessarily about a single pivot axis, to the first slidable member, the other end of the feed support member is both slidably and pivotally, again not necessarily about a single axis, attached to the second slidable member, and the first and second rails are shaped and positioned to maintain the feed in, or near to, said focal plane during movement of the feed support member along the first and second rails.

Abstract: A collision avoidance system for a vehicle has a vehicle steering sensor for sensing a direction in which the vehicle is being steered, a source of radiation, an articulated reflector for directing radiation from the source in a desired direction, an articulation mechanism for effecting articulation of the articulate reflector, and a close loop control circuit responsive to the vehicle steering sensor for controlling the articulation mechanism so as to cause the articulated reflector to direct radiation in a direction which is generally the same as that direction in which the vehicle is turning.

Abstract: The invention provides a reflector antenna, especially for a communications satellite, having at least one fixed main reflector (102) with an essentially circular aperture. A fixed feed system (118) includes a horn radiator (108) with a rotationally symmetric radiation diagram and a fixed polarization direction. An auxiliary reflector may be arranged to be rotationally positionable around a main axis (E) and has a reflecting surface that is shaped as a partial surface of a nonrotationally symmetric ellipsoid with a low numerical eccentricity, which illuminates main reflector (102) elliptically with an ellipticity that is essentially constant regardless of the rotational position.

Abstract: A composite antenna for use in satellite communication provides both the functions of multiple beams and a shaped beam radiated from a single radiating aperture. The radiating aperture may employ a mirror or a lens. Transmitted radiation from an array of radiators is coupled via a subreflector to the main reflector or lens which constitutes the radiating aperture of the antenna system. During reception of radiant-energy signals, signals received by the main reflector or lens are coupled via a separate subreflector to a separate array of receiving radiators operated at a frequency band different from that of the transmit array. The two subreflectors are combined into a single subreflector assembly employing a metallic concave reflector covered by a layer or coating of frequency selective optical material which allows for propagation of radiation at one frequency to the metal reflector while reflecting radiation in the other frequency band from a surface of the coating.

Abstract: A dual-reflector antenna system (40) is provided for generating a shaped main beam radiation pattern (20) and at least one additional secondary spot beam radiation pattern (30,32). The antenna system (40) includes a main shaped reflector (10) having a shaped reflective surface (11) operatively coupled to a subreflector (12) for communicating therewith. A main feed horn (14) communicates directly with the subreflector (12) so as to reflect first energy to and from the main reflector (10) within a shaped beam radiation pattern (20). In a preferred embodiment, the subreflector (12) has an ellipsoidal reflective surface (13) which communicates directly with the main reflector (10) via an inverted reflective path (17) which has a converging focal point (18). One or more auxiliary feed horns (24,26) are operatively coupled directly to the main reflector so as to directly communicate therewith and reflect second energy within one or more additional radiation patterns (30,32).

Abstract: An omnidirectional microwave antenna comprises a conical reflector and a conical feed horn. The conical reflector has a reflecting surface defined by a cone having an axis and a surface of revolution around the axis. The line of intersection between the surface of revolution and a plane passing through the axis and the surface of revolution is a segment of a parabolic curve. The reflector includes a flange extending outward from an outermost circumference of the surface of revolution of the cone. The conical feed horn feeds microwave energy to the conical reflector from a location along the axis of the cone. The feed horn has an aperture whose center is located approximately at the apex of the cone. The flange has absorptive material mounted thereto for absorbing microwave energy impinging thereon.

Abstract: A novel method for calculating the surface shapes for subreflectors in a suboptic assembly of a tri-reflector spherical antenna system is introduced, modeled from a generalization of Galindo-Israel's method of solving partial differential equations to correct for spherical aberration and provide uniform feed to aperture mapping. In a first embodiment, the suboptic assembly moves as a single unit to achieve scan while the main reflector remains stationary. A feed horn is tilted during scan to maintain the illuminated area on the main spherical reflector fixed throughout the scan thereby eliminating the need to oversize the main spherical reflector. In an alternate embodiment, both the main spherical reflector and the suboptic assembly are fixed. A flat mirror is used to create a virtual image of the suboptic assembly. Scan is achieved by rotating the mirror about the spherical center of the main reflector.

Abstract: An antenna system is described including a reflector antenna, responsive to radio frequency signals at a first frequency, having a first reflector surface, a second reflector surface and a Cassegrain feed. The antenna system further includes an array antenna having a plurality of antenna elements responsive to radio frequency signals having a second different frequency, wherein a center element is in a common location with the feed of the reflector antenna. With such an arrangement, an improved dual band antenna system is provided. By providing the center element of the array antenna in a common location with the feed of the reflector antenna, a dual band radio frequency antenna system is provided which is more compact with improved radiation characteristics than known similar configured antennas.

Abstract: Equalized offset fed east and west shaped reflectors (12) and (14) and technique for producing the same are provided herein. A first shaped reflector (12) has a first shaped reflective surface (3) formed to provide a first shaped beam radiation pattern (22). Dimensional deviations such as deviations (X) and (Y) are measured between the first shaped reflective surface (13) and a parent surface (30). A second shaped reflector (14) is formed with a shaped reflective surface (15) which has dimensional deviations superimposed on the other side of the parent surface (30). The second shaped reflector (12) is rotated 180 degrees relative to the first shaped reflector (14). The first and second shaped reflectors (12) and (14) are then placed in a configuration opposite one another and have shaped beam radiation patterns (22) and (24) which are substantially equal to one another. In addition, feed horns (18) and (20) are operatively coupled to the first and second shaped reflective surfaces (13) and (15) respectively.

Abstract: A multireflector antenna utilizes a frequency-selective surface (FSS) in a subreflector to allow signals in two different RF bands to be selectively reflected back into a main reflector and to allow signals in other RF bands to be transmitted through it to the main reflector for primary focus transmission. A first approach requires only one FSS at the subreflector which may be an array of double-square-loop conductive elements. A second approach uses two FSS's at the subreflector which may be an array of either double-square-loop (DSL) or double-ring (DR). In the case of DR elements, they may be advantageously arranged in a triangular array instead of the rectangular array for the DSL elements.

Abstract: A satellite television receiver antenna for use on seaborne vessels comprises a Cassegrain antenna including a parabolic main reflector, and a hyperbolic sub-reflector mounted at an angle slightly opposite from the center axis of the parabolic reflector, the sub-reflector being driven by a motor to rotate so as to cause the antenna reception pattern to perform a conical scan around the main axis of the parabolic reflector. The rotational speed is an even multiple of the frequency of any amplitude modulation of the received signal, or of any electrical interference, and the received signal is measured at points rotationally spaced apart 180 degrees, so that the effects of modulation and/or electrical interference are cancelled. The measured signal strength at four positions spaced rotationally by 90.degree. is used to derive power signals to drive pulse width modulation control azimith and elevation motors.

Abstract: A dual-mode, radio frequency, optical-wavelength detector apparatus includes RF-transparent optical elements adapted to focusing optical energy in a wavelength range including ultraviolet through infrared wavelengths, on an optical detector, and an RF antenna located behind the optical elements. One embodiment of the apparatus employs a Cassegrain infrared optical telescope system having a concave primary mirror, the front surface of which has applied thereto multiple layers of dielectric material comprising an interference filter reflective in a band of infrared wavelengths, and transmissive to radio frequency energy. A convex secondary mirror having a similar reflective coating is so located as to reflect infrared energy backwards through a central coaxial perforation through the primary mirror onto an infrared detector.

Abstract: A multi-spectral seeker system for detecting radiation in the infrared (IR) band and a plurality of radio frequency (RF) bands suitable for use in a guided missile is disclosed. The IR and RF seekers are coaxially integrated on a single gimbaled platform and share a common aperture without significant performance degradation. In the preferred embodiment, the IR seeker uses a Cassegrainian reflector assembly with surfaces reflective to IR but transparent to RF signals. The first RF seeker uses a resonant dichroic reflector antenna which is transparent to RF signals at frequencies no closer than 0.5 octaves from the dichroic reflector system operating frequency. The second RF seeker may use any suitable RF antenna system although a planar-array of multi-mode spiral antennas or a standard flat plate slotted array are preferred. The second RF seeker may operate in an active, semi-active, or passive mode.

Abstract: An antenna system for producing a millimeter wave beam having a Gaussian distribution uses a high power source and a partial mode converter operatively coupled to the source and reviving from the source a T.sub.m,n mode wave which might either be TE.sub.m,n or TM.sub.m,n'. The converter delivers a mixture of modes including the mode T.sub.m,n at a relative power rate of 70 to 85% and at a relative phase 0, and at least one of the following additional modes, namely T.sub.m,n-1 at a relative power rate of 10 to 20% and at relative phase .pi., and TE.sub.m,n+1 at a relative power rate of 10 to 20% and at relative phase .pi.. The mixture of modes is applied to a collimation reflector (3, 10), having a concentration point (5) constituting the antenna system outlet. The antenna system can convert any T.sub.m,n mode into a linearly polarized narrow beam of very high power (about 1 MW) and and of high frequencies above 100 GHz.

Abstract: A combined infrared-radar detection system wherein a radar antenna also serves as the primary mirror in an infrared focusing arrangement.

Abstract: The present invention is an integrated millimeter wave (MMW) and an infrared (IR) common aperture sensor employing a common primary reflector for infrared and millimeter wave energy. An active transmitter/receiver millimeter wave horn assembly located at the focus of the primary mirror transmits and receives millimeter wave signals off the primary reflector. A selectively coated dichroic element is located in the path of the millimeter wave energy on the axis between the feed and the primary reflector. The dichroic element reflects infrared energy from the primary reflector to a focal point and at the same time transmits and focuses millimeter wave energy. An optical system relays the infrared energy to a focal plane behind the primary mirror. The dichroic element transmits and focuses millimeter wave energy without significant attenuation such that optical and millimeter wave energy may be employed on a common boresight.

Abstract: A fixed feed dual reflector scanning antenna system 10 having a low moment of inertia is disclosed herein. The inventive dual reflector antenna system 10 includes an antenna feed structure 16 for emitting electromagnetic radiation. The antenna system 10 further includes a subreflector 12 for redirecting the emitted radiation. The subreflector 12 is intersected by a subreflector longitudinal axis L.sub.s at a rotation point proximate a vertex 20 of the subreflector 12. A main antenna reflector 14 circumscribing a main longitudinal axis L.sub.m projects radiation redirected by the subreflector 12 as an antenna beam. A mechanical arrangement 22 rotates the subreflector 12 about the rotation point so as to vary the angular orientation between the subreflector longitudinal axis L.sub.s and the main longitudinal axis L.sub.m. In this manner the antenna beam is scanned relative to the main longitudinal axis L.sub.m.

Abstract: A method and apparatus for monitoring moving vehicular traffic, especially adapted for the detailed profiling and counting of airport usage by aircraft employing Doppler radar and sound generated by target aircraft. A primary parabolic reflector operated in the Cassegrainian mode with respect to Doppler radar radiation, employed in combination with a hyperbolic sub-reflector constructed so that it will reflect the radar radiation but remain transparent to sound waves is used to propagate and receive radar radiation, and to receive sound waves emanating from a target aircraft. Sound waves emanating from the target are received by the parabolic reflector and directed toward the parabolic reflector's primary focus where they strike a microphone placed at the primary focus of such reflector. The signal from the microphone and the information from the Doppler radar unit are processed by a central processing unit to provide a variety of information relating to the target aircraft.

Abstract: A microwave antenna has a circularly symmetrical reflector made of a material having a liquid phase and a solid phase, with the reflector being obtained by centrifuging the material while in its liquid phase and then allowing it to pass into its solid phase. This results in a convex paraboloidal reflector face having a very high degree of surface accuracy. When housed inside a microwave absorbing ring connecting the reflector face to a microwave-transparent window and used with a suitable source held at a predetermined focus position between the reflector and the window by means of microwave absorbent triangular struts, the antenna demonstrates improved radio and mechanical properties. Alternately, the centrifugally cast convex paraboloidal reflector may be used as the main reflector in a hybrid Cassegrain optical system in which the subreflector has a "conformed" non-paraboloidal surface that is machined from a solid piece of material.

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 triplex microwave reflector which includes a primary reflector and a pair of dichroic surfaces disposed between the primary reflector and the focal point of the primary reflector. Each of the dichroic surfaces reflects a specific band of microwave signal frequencies and transmits the others. Microwave signals reflected by one of the dichroic surfaces are focused at a front virtual focal point and microwave signals reflected by the other dichroic surfaces are focussed at a back virtual focal point. Microwave signals transmitted by both the front and back dichroic surfaces are focussed at the primary focal point.

Abstract: A method and apparatus for monitoring moving vehicular traffic, especially adapted for the detailed profiling and counting of airport usage by aircraft employing Doppler radar and sound generated by target aircraft. A primary parabolic reflector operated in the Cassegrainian mode with respect to Doppler radar radiation, employed in combination with a hyperbolic sub-reflector constructed so that it will reflect the radar radiation but remain transparent to sound waves is used to propagate and receive radar radiation, and to receive sound waves emanating from a target aircraft. Sound waves emanating from the target are received by the parabolic reflector and directed toward the parabolic reflector's primary focus where they strike a microphone placed at the primary focus of such reflector. The signal from the microphone and the information from the Dopple radar unit are processed by a central processing unit to provide a variety of information relating to the aircraft.

Abstract: An antenna adapted for millimeter wave applications has a dielectric lens with metalized reflective surfaces and uncoated refractive surfaces. A subreflector and polarization grating are provided on the central portion of a refractive surface.

Abstract: A rotating reflector is used to provide a beam scan throughout a predetermined angle such as 360.degree.. A circular polarizer is coupled with the reflector and converts received linearly polarized energy into circularly polarized energy. A fixed feed is configured to receive the reflected circularly polarized energy and converts such energy to linearly polarized energy. The antenna system can receive the same linear polarization of energy throughout its 360.degree. scan angle without polarization mismatch or orthogonal polarization losses. The relative orientation of the two polarizers may be adjusted to receive any orientation of linear polarization of energy throughout the scan angle. For example, they may be oriented so that the antenna system receives vertically polarized energy, slant 45.degree. linearly polarized energy, or horizontally polarized energy.

Abstract: A broadcasting receiver for vehicles especially suited for receiving satellite broadcasting signals comprises a base plate rotatable horizontally, a main reflector tiltably attached to the base plate, a sub-reflector attached to the end portion of an arm of which the other end is attached to the base plate so as to be rotatable horizontally, and a signal detector fixed to the main reflector. The vertical angle between the main reflector and the arm are maintained at a predetermined angle, and the sub-reflector which is arranged to be rotatable around the end portion of the arm is caused to stand up when the main reflector is in a stand up position. All devices and parts arranged on the base plate including the arm and the sub-reflector are covered by the main reflector when the main reflector is turned down.

Abstract: A multi-spectral imaging apparatus with a common collecting aperture, which combines a high performance infrared imaging system with a high performance millimeter wave transceiving system. Two mirror surfaces are combined with a refractive corrector in the infrared mode and with a single reflective parabolic antenna in the millimeter wave mode. The dual mode system functions well in a scanning as well as a staring configuration.

Abstract: An inverted offset system is used for sending and/or receiving electromagnetic energy. The system, which is preferably a Cassegrainian microwave antenna system, includes a water-tight cover to protect the feed compartment, subreflector, and main reflector of the antenna. The cover protects against the effects of precipitation and is especially useful when the system is used for measuring atmospheric conditions such as rain or snow. A waterguard ridge and drain passageway are used to protect the feed compartment from precipitation when the antenna is disposed in a position to send or receive beams which are substantially vertical.

Abstract: An earth terminal for a satellite communication system incorporates an oval or eliptical shaped antenna 1 whose horizontal dimension d.sub.1 is greater than it's vertical dimension d.sub.2. The relatively small dimension d.sub.2 allows the antenna to be transported by road while at the same time giving a beam shape which is broader in elevation than in azimuth. This special beam shape gives certain advantages which are described in the specification.

Abstract: A microwave reflector having metallic surfaces and nonmetallic surfaces is perfectly reflecting for the waves of a first polarization and partly transparent for the waves of a second polarization orthogonal to the first. The reflector is primarily applicable to radar systems.

Abstract: An antenna system wherein the feed assembly is rotated to provide spatial polarization stabilization with respect to vehicle movement so that orthogonal polarizations can be used simultaneously.

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: 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: This structure for a dichroic antenna can be used in a reflector antenna capable of operating at the same time at two different frequencies or with two orthogonal polarizations, and presents mechanical characteristics allowing its use on board the satellites. The structure, suitable for a subreflector, comprises a plurality of layers with high mechanical stiffness in the external part, followed by layers with low dielectric constant and one or a plurality of metallic grids in the most internal part, separated by low-dielectric constant layers.

Abstract: A device for receiving dual polarized microwave signals, including a first waveguide connected to a receiving antenna and to a first substrate bearing a first sensor perpendicular to the longitudinal axis of the first waveguide, a second waveguide having the same longitudinal axis and the same dimensions as the first waveguide, and which is connected to a second substrate having a second sensor perpendicular to the longitudinal axis of the second waveguide. Surrounding the second waveguide is a tube having tongues at opposed ends which cooperate with slots formed in the first and second substrates. The opposed tongues of the tube are staggered by 90.degree. so that upon insertion of the opposed tongues of the tube within the slots of the first and second substrates, sensors formed on these substrates are arranged orthogonally with respect to one another. The tongues and cooperating slots assure mechanical integrity.

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.