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: A bifunctional antenna of a primary/secondary radar system comprises a reflector having a concave front surface illuminated by a source of primary radiation and formed with a row of circular ports along a horizontal generatrix, the ports lying forwardly of respective cavities or waveguides of cylindrical configuration excitable to emit circularly polarized secondary radiation. In some embodiments the polarization may be changed to a linear or an elliptical mode under the control of inserts rotatable about the cavity axis.

Abstract: The crosspolarization components radiated by adjacent orthogonally linearly polarized feed horns of a reflector antenna system are compensated by structural modifications incorporated in the feed horns. In a first embodiment, the modified feed horns have curved walls and included shaped septa. Other embodiments involve the use of shaped walls or shaped septa only. In the case of an offset reflector, asymmetric modifications of the wall shape and septa are employed. For flared feed horns with rectangular cross section, the crosspolarization compensation is provided by curving the forward edges of the horn walls convexly or concavely as required.

Abstract: Apparatus for converting the polarization of electromagnetic waves from linear polarization to circular polarization wherein a plurality of layers of meandering electrical conductors are formed into a sandwich mounted one above the other wherein at least some of the conductors on different sandwich layers are in phase with each other but in which at least one of the electrical conductors on at least one of the sandwich layers are formed so that adjacent or some of the conductors are not in phase with each other but are phase offset such that the composite structure produces improved circular polarization as compared to polarization converters of the prior art. The sandwich structure according to the invention can be utilized as integrated into a radome of a tracking radar antenna for example.

Abstract: An omni-directional type passive antenna in which the response pattern is a close approach to the ideal of a hemisphere. The system includes an antenna having an antenna axis extending in the direction of highest antenna sensitivity, and a first surface which is a surface of revolution swept out by a part of a parabolic curve rotated about the antenna axis, the axis of the parabolic curve being inclined at an angle in the range of about 70 to 80 degrees to the antenna axis with the focus of the parabolic curve substantially on the antenna axis. A first set of electrically isolated dipoles is mounted on the surface and all are similarly oriented such that they lie only along edges of axial planes of the antenna.

Abstract: A radio frequency antenna is provided wherein an array of antenna elements is adapted to establish linearly polarized radio frequency energy. A polarizer means is disposed between the array of antenna elements and free space for converting the linearly polarized radio frequency energy associated with the antenna elements into circularly polarized radio frequency energy in free space, such polarizer means being disposed about a frontal portion and side portions of the array antenna elements. A polarization filter means for rejecting radio frequency energy having a selected linear polarization is disposed between the side portions of the array of antenna elements and the polarizer means. In a preferred embodiment of the invention, the polarization filter is disposed to reject radio frequency energy having a linear polarization, such linear polarization being disposed at an acute angle with respect to the linear polarization provided by the antenna elements.

Abstract: A radar antenna of the Cassegrain type comprises a paraboloidal principal reflector confronting a hyperboloidal or flat auxiliary reflector of smaller radius directing linearly polarized radiation from a source on their common axis toward the principal reflector along lines passing through the focal point thereof to produce an axially extending outgoing beam whose central part is intercepted by the auxiliary reflector. The latter consists of an array of linear conductors generally parallel to the direction of polarization while the principal reflector is formed by another conductor array generally inclined at 45.degree. to that direction, the latter array being backed by a solid mirror separated therefrom by a distance smaller than a quarter wavelength at the midfrequency of the emitted radiation.

Abstract: Metallized sheet-form textile materials of synthetic polymers or natural fibres, to which a metal layer has been applied by currentless wet-chemical deposition, are particularly suitable for use as reflectors for electromagnetic waves in the range from 10 MHz to 1000 GHz. In the case of stretched metallized fabrics, the reflecting radiation is partly polarized which can facilitate or improve the recognition of an object by radar beams. By periodically stretching and relaxing the fabric, it is even possible to modulate the reflected microwaves.

Abstract: An aperture antenna having the improved phase performance of radiated co- and cross-polarization has been found. The present antenna has, at least, a horn for radiating an electro-magnetic wave, and means for focusing the electromagnetic wave. The focusing means is actually implemented by a reflector or a dielectric lens, and is designed so that the phase distribution of an electric field on an aperture plane of the focusing means has the period of .pi./2 and the maximum phase at (2m-1) .pi./8 from the reference plane of one polarized wave in the polar coordinates system on the aperture plane, where m is an integer.

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: A bifunctional antenna of a primary/secondary radar system comprises a reflector having a concave front surface formed with a row of slots along a horizontal generatrix, the slots lying in front of respective cavities excitable to radiate interrogation signals in a directive sum pattern and supplemental radiation in a differential control pattern designed to blank minor lobes of the interrogation pattern. Some of the cavities and slots are symmetrically duplicated on a dielectric cap covering the convex rear surface of the reflector. The reflector and its cap form a closed shell of dielectric material, specifically a glass mat impregnated with epoxy resin, overlain at the front by a fiber-glass fabric incorporating orthogonally intersecting insulated copper wires.

Abstract: A microwave polarization transformer comprises a number of dielectric plates each having embedded therein one or two networks of parallel conductive wires in which switchable diodes are inserted. The plates are perpendicular to the direction of propagation of the waves on which they act and so oriented that the general direction of the wires of each network includes an angle of 45.degree. with the direction of the electric field of the linearly polarized incident wave.

Abstract: A luneberg type passive reflector for circularly polarized waves consists of a woven cloth made partially of conductive wires located within the dielectric sphere the surface of which is covered with a set of parallel wires perpendicular with the conductive wires in said cloth. The conductive wires of the cloth are less than five hundredths of wavelength in diameter and their spacing is between 1/4 and 1/20 of a wavelength. The wires interwoven with said metal wires to form the cloth are preferably made of flax.

Abstract: Inverse Cassegrain antenna making it possible to use on the one hand the qualities of a conventional fine beam for look-out and tracking functions and making it possible on the other hand to have a widened beam either in the elevation plane or in the bearing plane. According to one embodiment, this antenna is provided with a mirror constituted by two reflector - polarizer elements joined to one another by a hinge which permits the articulation thereof, a remote control device regulating their relative orientation.

Abstract: A feature of this invention is the provision of an antenna system providing two, coaxial, copolarized, independently focused beams: a relatively wide, low frequency, searching beam, and a relatively narrow, high frequency, tracking beam; and comprising a dual frequency, dual polarization feedhorn; a polarization dependent subreflector; a concave polarization reversing reflector; a concave polarization twisting reflector; and a planar frequency dependent dielectric lens.

Abstract: There are herein described microwave devices that are mounted at the output ends of circularly polarized horn antennas of a microwave antenna array. The devices act as coupling compensators between the horns, and also function as singular or dual polarization trimmers to create very low axial ratio circularly polarized antenna array patterns through a broad angular range. In each of these devices, a parasitic element is disposed on a planar substrate that is orthogonally positioned with respect to the direction of propagation from the horn antennas.

Abstract: A 360 degree fan beam scanning antenna which includes a transreflector created by a plurality of reflecting elements arranged on a surface of revolution formed about a generating axis and a feed antenna rotatable about the internal focal circle of the transreflector that provides an illumination beam for the transreflector which minimizes spillover and antenna pattern skewing.

Abstract: A radome having arrays of thin strips of dielectric material on both the inside and outside walls of a conical shell defined by a sheet of dielectric material for compensating for the polarization dependent phase delay of the radome shell is disclosed. The strips of the outside array are supported edgewise on the outside wall and are normal thereto. The outside strips are equally spaced from each other, and disposed so that the intersection of lines extending therefrom is at the vertex of the shell. The strips of the inside array are supported edgewise on the inside strips wall. The inside strips are spaced from one another and tilted from the inside wall at an angle of approximately 45 degrees in a direction away from the vertex of the shell. Each of the inside strips is a frustum of a cone disposed with its axis along the axis of the shell. The tilt of the inside strips increases the transmittance bandwidth of the radome and further decreases dependence of phase delay upon the angle of incidence.

Abstract: Disclosed is an antenna feed system for use in satellite communication systems and the like, comprising a horn with a rectangular aperture and a waveguide connected thereto. The assembly formed by the waveguide and horn is constructed from two parts secured together so that the junction lies in the longitudinal symmetry plane parallel to the electric field of the TE.sub.01 mode and is mounted for rotation about the longitudinal axis of the waveguide. The feed system further comprises a polarization converter mounted in front of the horn for rotation about the extention of the longitudinal axis of the waveguide. The converter is constructed from a plurality of layers of supporting material each provided with a conductor which forms in one direction a mainly inductive load and in a direction which is perpendicular thereto a mainly capacitive load.

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

Abstract: A horn antenna is disclosed having a built-in circular polarizer and a cross polarization attenuator. A square-apertured horn antenna has a plurality of pairs of conductive fins disposed along opposite edges of the horn interior. The individual fins are separated from each other by approximately one-fourth wavelength. The fins are at a 45 degree angle to that linear wave and react with that linear wave by imparting a circular rotation to that wave as the wave propagates past each pair of fins. A stepped attenuator is mounted in the input section to the horn antenna perpendicular to the linear input wave. The attenuator substantially absorbs cross-polarized signals whether reflected from the aperture of the horn or provided by the incoming signal.

Abstract: A conical horn antenna is disclosed having dual dielectric bands mounted therein for improving the rotational symmetry or elipticity of the radiated beam as well as the efficiency. The first and second dielectric bands are coaxially mounted to each other and to the conical horn. The lengths of the bands are determined by the frequencies being propagated. A circularly polarized dominant wave such as TE.sub.11 mode is applied to the antenna and excites a series of higher order waves such as the TM.sub.11 mode. The circularly polarized dominant and the higher order modes are propagated toward the aperture where they are in phase and therefore add vectorially. The dual dielectric band acts as a slow wave structure and higher order waves which in turn provide an improved phasing between the dominant modes.

Abstract: A multibeam antenna having a radio frequency lens fed by a plurality of feedports is disclosed. The radio frequency lens includes a printed circuit parallel plate region and a polarizer section. The polarizer section includes a plurality of polarizer sheets separated by a plurality of layers of dielectric material, the dielectric constant of the printed circuit parallel plate region and the dielectric constant of the layers of dielectric material being selected to form substantially collimated beams, each one of such beams being associated with a corresponding one of the feedports. With this arrangement, the polarizer section is an integral part of the radio frequency lens, thereby reducing the size of the antenna.

Abstract: A microwave system is disclosed for simultaneous amplification and radiation of CW and pulsed signals wherein signals from a CW amplifier tube and a pulsed power amplifier tube are transmitted to an antenna where they are radiated as signals with circular polarizations of opposite direction. In one embodiment interstage circuitry between the amplifiers and the antenna includes a magic "T" hybrid and a 90.degree. phase shifter.

Abstract: A polarization selective screen allowing only electromagnetic waves having a desired linear polarization to pass therethrough, the screen includes an array of relatively thin, parallel and evenly spaced conductive flat ribbons supported between end portions of a frame structure, the broad surface of the ribbons being orthogonal to the plane of the screen and being supported and maintained in place under a predetermined tensional force by tension means such as spring-loaded ribbon hangers.

Abstract: A dual circularly polarized radiating and receiving arrangement is coupled to a dual circular polarizer which has coupled thereto a transmit port and a receive port. A circuit arrangement is coupled to both of the ports to enable radiation of a selected one of vertical linearly polarized waves, one of right hand and left hand dual circularly polarized waves and linearly polarized waves having a selected angle of polarization and reception of the other of the right hand and left hand dual circularly polarized waves.

Abstract: A multisided horn antenna such as a square horn is disclosed having an improved axial ratio circular polarization or ellipticity. Ellipticity of a square horn antenna is improved by placing a conical section or ring of conductive material at the aperture of a horn antenna. The conical ring causes a relatively directive beam having a low axial ratio to be produced throughout most of the pattern generated similar to that of a conical horn antenna. Yet, the square horn antenna provides increased power over a conical horn.

Abstract: The polarization properties of the field radiated from a polarization grid have been found to be similar to those in the aperture of an offset curved focusing reflector. Therefore, broadband cancellation of the polarization rotation in a large offset reflector is substantially accomplished in the present invention by the opposite prerotation of the incident feed radiation via a polarization grid. For maximum cancellation the polarization grid, having parallel spaced-apart elements, is disposed at an angle to a plane normal to the feed axis of the offset reflector which approximates one-half of the value of the angle between the feed axis and the offset reflector axis.

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 horn for radiating circularly polarized energy includes a rear launcher section commencing with a double-ridged cross section and ending at the horn flare with a square cross section with the plane of polarization so that the wave excited in the square cross section is along a diagonal of the square. The horn flare section opens up to a dimension of approximately 70% larger than the square throat dimension to narrow the elevation beam. A dielectric slab oriented in the horizontal plane is seated in the flare section for introducing a frequency-varying differential phase shift between orthogonal modes for effectively compensating for the inherent phase shift in the flare. Refracting lenses that are half-cylinders having a diameter of about 25% of the horizontal aperture dimension with their axes aligned vertically are located close to the vertical aperture edges for refracting the energy at the horn edges into the region between 30.degree. and 60.degree. from the horn axis.

Abstract: A broadband antenna system of small dimensions and composed of at least one antenna having an associated design operating frequency, and a plurality of reflectors operatively associated with the antenna and disposed at respectively different distances therefrom, each reflector being spaced from the antenna and having a reflection characteristic to be optimally matched with the antenna for operation at a respective partial frequency band, each reflector being associated with a different partial band such that the total operating frequency range of the system is divided into a plurality of partial bands equal in number to the number of reflectors and covering the design operating frequency range and a further frequency range below the lower limit of the design range, whereby the antenna characteristics are improved, and in particular the operative bandwidth of the system is increased in the low frequency direction.

Abstract: Interference from polarized signals is minimized by controlling the polarization of antennas having orthogonal dipole radiating elements. The antenna system utilizes microwave hybrids and phase shifters in a coaxial cable feed circuit that divides the power between horizontal and vertical dipole radiating elements. The circuit provides a variable antenna polarization that can be controlled to discriminate against interfering signals having any given polarization characteristics. Coaxial double folded baluns connect feed circuits to the dipole radiating elements and provide proper phasing and impedance transformation for efficient dipole operation.

Abstract: A system filter for double frequency utilization, including a broadband polarization filter in conjunction with frequency filters for separating two different frequency bands with each frequency band being doubly orthogonally polarized. The broadband polarization filter of singly symmetrical construction includes a doubly polarizable waveguide section which is axially divided by means of a partition into two symmetrical partial waveguides and the two frequency bands of the wave which is polarized parallel to the partition are each coupled out through a respective coupling window in two oppositely disposed walls of the waveguide section into a respective waveguide tee.

Abstract: Disclosed is a coaxial waveguide antenna. In a basic form the coaxial waveguide horn for the antenna comprises an inner section operating in a .SIGMA. (sum) mode only and an outer section operating in a .DELTA. (difference) mode only. Where required for broadband (i.e., for more than 1 octave), intermediate sections operating in .SIGMA. and .DELTA. modes are provided. The basic structure operates in the linear mode; for polarization diversity and circular polarization, a polarizer is placed in front of the horn, or a dielectric sheet is positioned within a coaxial waveguide section at an angle of 45.degree. as to the E field, or by feeding the coaxial waveguide with six or more number of probes.

Abstract: The polarization control of the antenna is obtained by space feeding the nals through a polarization control rotator to a monopulse feedhorn.

Abstract: A parabolic dish is constructed by forming from relatively thin flexible sheet material a planar assembly of relatively narrow curved strips arranged side by side and having arcuate longitudinal edges which conform to curves defined by certain parametric equations, such that the strip assembly may be deformed to a parabolic dish configuration wherein the adjacent strip edges are disposed contiguous one another in planes parallel to a plane containing the principle axis of the dish, and joining the strips of the deformed strip assembly to retain the latter in its parabolic dish configuration.

Abstract: Improvements are made in a dual frequency echo cancelling assembly for mounting in a hole in the subreflector of a Cassegrainian antenna. Subreflector echo returned to the feed system is cancelled in two frequency ranges by a reflection from the echo cancelling assembly which includes a flat plate, a guard ring surrounding the plate, and a conductive grid between the plate and the feed system. The improvements include wide, thin grid conductors electrically connected to the guard ring and a ring of reflective or absorptive material surrounding the guard ring to cover the subreflector hole edge. When the improved assembly is adjusted for best performance, a stronger reflection in the direction of the feed system is obtained for echo cancelling without sharp resonance peaks. The required diameter for the improved dual frequency echo cancelling assembly is smaller, minimizing blockage of the subreflector and undesirable scattering.

Abstract: A monopulse radar antenna having an improved three-channel feedhorn for piding selectable polarization and greater target discrimination. The antenna feed employs a comparator having a difference port, a first sum port, and a second sum port utilizing a coupling pin or probe therein, between the comparator ports and an adjustable polarization device, for receiving and separating returned energy which has become cross-polarized with respect to the polarization of the transmitting sum arm, by reflection from an asymmetrical target. The three-channel feedhorn makes possible the identification of different types of targets, and the detection of hidden targets in rough terrain, forests, underbrush, and rough seas.

Abstract: A Luneberg lens with a polarization-sensitive spherical "leaky" reflector cap having conductive strips aligned at a 45.degree. angle to the linear polarization of the incident wave. The ratio of strip width to strip spacing is preferably chosen to reflect back a cross-polarized component about -10 db below the reflected self-polarized component. The strip width is small as compared to the focal spot diameter of the lens for any given incident wave direction and also small as compared to the wavelength of the incident wave. The lens and reflector can be used in small drone aircraft to simulate the radar cross section of a larger body such as an aircraft whose radar cross section causes reflected polarization components not present in the incident field. The full specification must be consulted for an understanding of the invention.

Abstract: An integral element/phase shifter for use in a phase scanned array. A non-resonant waveguide or stripline type transmission line, series force feeds the elements of an array. In the embodiments shown, four RF diodes are arranged in connection within the slots of a symmetrical slot pattern in the outer conductive wall of the transmission line to vary the coupling therefrom through the slots to the aperture of each individual antenna element. Each diode thus controls the contribution of energy from each of the slots (at a corresponding phase) to the individual element aperture and therefore determines the net phase of the said aperture. Three species of the invention are shown, the first and second involving RF diodes in the slots of waveguide broad and narrow walls respectively, and the third having slots through the shield plane of a stripline. The invention facilitates array phase scanning without the need for separate, and relatively more expensive, discrete phase shifters for each antenna element.

Abstract: A compact device for launching circularly polarized electromagnetic waves utilizes a hollow waveguide terminated by a horn. Within that structure, a septum fin extends from the waveguide into the horn. The septum fin divides the hollow waveguide into two smaller waveguides, each of which is capable of independently supporting the TE.sub.1,0 mode of wave propagation. The fin is a tapered plate that has its maximum width within the waveguide and its minimum width in the horn. A signal injected into one port of the divided waveguide emerges from the horn as a circularly polarized wave having its polarization vector rotating clockwise whereas a signal injected into the other port emerges from the horn as a circularly polarized wave with its polarization vector rotating in the counter clockwise direction.

Abstract: A compact offset Cassegrainian antenna having a paraboloidal main reflector and a convex subreflector brings microwave beams to a focus. A small flat reflector placed in one of the beams at the focus deflects it for interception by a concave reflector and horn. Another beam passing by the flat reflector is intercepted by a second concave reflector and horn. The flat reflector is smaller than a focally located horn, allowing more closely-spaced beams to be accommodated. The flat reflector may be replaced by a curved reflector, a prism, or a microwave lens. Another flat reflector is added for each additional beam. Polarized beams are accommodated by adding a polarization screen.

Abstract: A multiplexer-demultiplexer operates in the 3.6 to 4.2, 5.9 to 6.4, 6.4 to 7.1 and 10.7 to 11.7 kmc. The multiplexer-demultiplexer first picks off the signals of the first frequency band, and thereafter separates the signals of the fourth frequency band from other frequency bands, comprising the second and third frequency band, of the input signals, all these operation being performed for each one of the vertical and horizontal polarizations. The aforesaid other frequencies are thereafter separated according to polarization only before it is demultiplexed according to frequency.

Abstract: A dual frequency band horn-type antenna feed is described which has primary application to optimally illuminate a parabolic cylindrical reflector operating simultaneously at high power in both of the two bands. The principle of the invention is applicable to any two frequency bands regardless of their frequency separation including coincidence as a limiting case. The basic requirement of such a feed is that it must be as directive as possible within constraint of the feed aperture size in the plane of the cylinder axis because the cylindrical reflector does not collimate the beam in this plane and it must be relatively nondirective in the plane of the parabola for efficient illumination of the reflector. This requirement requires the phase front in the directive plane to be controlled within a small fraction of a wavelength at both frequencies.

Abstract: A rotatable radar antenna feed and receiver horn having two summing ports d a difference port with a rotatable section having a plurality of susceptor pins to rotate the polarization of the transmitted and received electromagnetic energy to reduce or minimize clutter and to enhance a target.

Abstract: An antenna element for use in a phased array antenna is disclosed. Such antenna element is a reciprocal device adapted selectively to radiate radio frequency energy of either circular or linear polarization. Such antenna element includes waveguide means for passing radio frequency energy and for radiating such energy; and means adapted to transform the polarization of the radio frequency energy as such passes through the waveguide means to radiate such radio frequency energy selectively with either linear or circular polarization. In a preferred embodiment the just-mentioned means includes a first and a second nonreciprocal quarter-wave plate having field orientations effectively 45.degree. with respect to each other. Such nonreciprocal quarter-wave plates flank a third nonreciprocal quarter-wave plate switchable so that its field orientation is either aligned with the field orientation of the first nonreciprocal quarter-wave plate or, while still aligned as before, turned 180.degree..