Abstract: The present application discloses a horn antenna, including a frequency selective surface (FSS), a connection structure, and a waveguide tube. The connection structure includes a first dielectric slab, a second dielectric slab, and a dielectric wall, which jointly form a hollow structure. A first surface of the first dielectric slab is a hyperboloid whose surface is protruding, a second surface of the first dielectric slab is connected to the dielectric wall. The dielectric wall has a tubular structure, a first surface of the dielectric wall is covered by the first dielectric slab, a second surface of the dielectric wall is covered by the second dielectric slab. There is a hole at a middle position of the second dielectric slab. The FSS covers the first surface of the first dielectric slab. A part of the waveguide tube is inserted into the hole of the second dielectric slab.

Abstract: An antenna system capable of achieving simultaneous transmit and receive (STAR.) operation over a wide bandwidth includes a ring array of TEM horn elements and a centrally located monocone or bicone antenna. The TEM horn elements each include a capacitive feed. The elements of the ring array are excited using a phasing scheme that results in signal cancellation, at the location of the central element. The ring array may serve as either the transmit antenna or the receive antenna.

Abstract: A communications system includes a satellite hub, a remote satellite terminal, and a satellite configured to provide communications therebetween. The remote terminal includes a controller that functions as an enforcement mechanism when adjusting antenna polarization on the remote satellite terminal to facilitate communications with the satellite. The satellite transmits an acquisition signal at a first satellite polarization angle, and a jamming signal at a second satellite polarization angle different from the first satellite polarization angle. If the polarization is not set correctly, then the jamming signal is not filtered by a narrow width null of the receive gain pattern at the remote satellite terminal, and the controller inhibits transmission. This forces an installer to correctly set the polarization of the antenna at the remote satellite terminal.

Abstract: A feed assembly for a parabolic dish reflector is described. The feed assembly includes a waveguide cavity locatable at the focal point, or any other desired off-boresight location corresponding point, of the parabolic dish, at least one first radiating element optimized for operation at a first frequency band and provided on a top surface of the waveguide cavity, and a plurality of second radiating elements each optimized for operation at a second band of frequencies and provided on the top surface of the waveguide cavity.

Abstract: An antenna, including a broadband bi-conical antenna including a lower antenna element and an upper conical antenna element, the lower antenna element including a lower conical antenna element and a meandered counterpoise element, which meandered counterpoise element is disposed at a base end of the lower conical antenna element and is integrally formed therewith, a reflector having a projection in a plane generally perpendicular to a vertical axis of the bi-conical radiating element, and a feed arrangement for feeding the bi-conical radiating element.

Abstract: A radio communication system according to the present invention includes a scatterer configured to reflect, refract, or transmit a radio wave radiated primarily from a transmission side apparatus to radiate the radio wave secondarily to a desired area and a metamaterial is used for the scatterer.

Abstract: Electronic devices may be provided with antennas. The antennas may include conductive antenna cavities. Antenna resonating elements may be mounted in the antenna cavities to form cavity antennas. An antenna cavity may be formed from metal structures with curved edges that define a curved cavity opening. A flexible printed circuit substrate may be coated with a layer of metal. Slot antenna structures such as a directly fed antenna slot and a parasitic antenna slot may be formed from openings in the metal layer. The flexible printed circuit substrate may be flexed so that the antenna resonating element forms a non-planar curved shape that mates with the opening of the antenna cavity. A ring of solder may be used to electrically seal the edges of the cavity opening to the metal layer in the antenna resonating element. The curved opening may be aligned with curved housing walls in an electronic device.

Abstract: Radio frequency identification (RFID) tag assemblies and methods having an RFID semiconductor chip, a conductor and an antenna, the RFID semiconductor chip has an antenna interface mounted on a mounting surface of a mounting substrate and a predetermined operating frequency, the conductor is electrically coupled to the antenna interface of the RFID semiconductor chip, and the antenna is electrically coupled to the conductor and includes a first radiating element lying in a first plane and a second radiating element lying in a second plane that is at an angle relative to the first plane.

Abstract: The antenna may include a planar reflector having a plurality of loop electrical conductors defining an array of parasitically drivable antenna elements, and a circularly polarized antenna feed spaced from the planar reflector to parasitically drive the array of parasitically drivable antenna elements and impart a traveling wave current distribution therein. The antenna may have properties that are hybrid between parabolic reflectors and driven arrays, providing a relatively compact circularly polarized antenna capable of having low wind load. Closed circuit or loop elements may provide increased gain over antennas using dipole turnstile reflector elements.

Abstract: An antenna assembly includes a reflector having a focal plane, a first feed element located along the focal plane that illuminates the reflector to create a first contour beam at a first frequency and a second feed element located further from the reflector than the first feed element that illuminates the reflector to create a first spot beam at a second frequency, the second frequency being different than the first frequency.

Abstract: A band clamp for coupling a radome to a distal end of a reflector dish for improving the front to back ratio of a reflector antenna, the band clamp provided with an inward projecting proximal lip and an inward projecting distal lip. The distal lip dimensioned with an inner diameter equal to or less than a reflector aperture of the reflector dish. The proximal lip provided with a turnback region dimensioned to engage an outer surface of a signal area of the reflector dish in an interference fit. A width of the band clamp may be dimensioned, for example, between 0.8 and 1.5 wavelengths of an operating frequency.

Abstract: The invention relates to an antenna for transmitting or receiving electromagnetic waves at a working frequency fT, that comprises a resonator with a filtering (49) coating that covers the major portion of the upper face of a reflector (22) located inside a cavity (36), the coating (40) being capable of removing all the electromagnetic waves having a frequency fT, and propagating in a direction parallel to the upper face of the reflector, without removing all the electromagnetic waves having a frequency fT and propagating in a direction perpendicular to the upper face of the reflector.

Abstract: An integrated antenna and reflector feed is provided which is structured as a waveguide cavity antenna or array having a curved reflector coupled to a sidewall of the waveguide cavity. A radiation source is situated facing the curved reflector and one or more radiating elements are provided on a top surface of the waveguide cavity. Several curved reflector feeds may be used, operating in the same or different frequencies.

Abstract: The reflectarray comprises an array of patch elements (10-13). Each patch element has a cut ring shape formed of a conductive ring with at least one crossing gap. The outer diameter and inner diameter and crossing gap are adjusted so that a phase shift ? defined by the following relations is different from zero: ?(Eox)=?(Eix)+? (1) ?(Eoy)=?(Eiy)+?+? (2) where: ??(Eox) and ?(Eoy) are the phases of the orthogonal components and of the reflected wave, respectively, ??(Eix) and ?(Eiy) are the phases of orthogonal components and of the incident wave, respectively, ?? is a phase angle.

Abstract: Reflections on the aerial system of a fill level radar result in reduced measuring quality at short range. Small echo signals at short range can thus disappear in the noise. According to one embodiment of the present invention a parabolic aerial for a fill level radar is stated, which parabolic aerial comprises a parabolic mirror, an exciter and a diffusion disc. The diffusion disc is used for laterally removing interfering electromagnetic waves that would otherwise be absorbed by the exciter. In this way the decay behaviour at short range can be reduced.

Abstract: The invention concerns an antenna system for level measurement with a level measurement device with a wave guide (5) that runs axially and that either has on its rear side an arrangement (4) for the generating and interpreting electromagnetic waves or can be connected to such an arrangement of an antenna, in particular, a parabolic antenna (1-3) on the front side of the wave guide and a wave adapter (9) for transmitting such a wave between two components of the arrangement that conduct the wave for adaptation of the wave transmission between the components, whereby the wave adapter has a through opening in the axial direction.

Abstract: A compact broadband antenna. The antenna includes a first mechanism for receiving input electromagnetic energy. A second mechanism provides radiated electromagnetic energy upon receipt of the input electromagnetic energy. The radiated electromagnetic energy is provided via an antenna element having one or more angled surfaces. A third mechanism directs the radiated electromagnetic energy in a specific direction. In a more specific embodiment, the third mechanism includes a reflective backstop that is selectively positioned behind the second mechanism to reflect back-radiated energy forward of the second mechanism, thereby causing reflected electromagnetic energy to combine in phase with forward-radiated energy from the second mechanism. The third mechanism further includes plural layers of dielectric material.

Abstract: An antenna which includes a monoconical antenna feed assembly, where the feed assembly has a base and an apex, a ground plane adjacent to the monoconical antenna feed assembly near the apex, and an antenna reflector coupled to the ground plane, where the antenna reflector at least partially surrounds the monoconical antenna feed assembly. The monoconical feed point is used to drive a reflector antenna. The broadband characteristics of the monoconical image vertical antenna (typical ground plane geometry) are used as the feed point for the reflector to give modest amount of gain while maintaining larger than previously developed bandwidths.

Abstract: Configurable antenna, adapted to transmit or to receive at least one beam of electromagnetic radiation in a direction and over an angular width that are adjustable. The antenna includes an antenna that is omnidirectional about a given axis z. The omnidirectional antenna comprises at least one biconical antenna and the configurable antenna further comprises controllable reflectivity discrete reflector elements passing through the cones of the omnidirectional antenna without electrical contact and disposed on at least one circle centered on the given axis z. The antenna is applicable to mobile telephony.

Abstract: An apparatus includes a microwave source that produces a microwave feed beam, and a first pair of microwave sensors that each intercept and receive a portion of the microwave feed beam. The two microwave sensors are spaced apart from each other along a first-pair axis. A first phase-comparison device has as it inputs the output signals of the two microwave sensors, and as an output a first phase comparison of the first-sensor output signal and the second-sensor output signal. A first geometrical calculator has as an input the first phase comparison and as an output a geometrical relationship of the first-pair axis to an other feature. This geometrical relationship output may be used to generate a control signal that is used to alter the geometrical relationship. There may be additional microwave sensors operating in a similar manner but spaced to provide information for other geometrical axes or allow improvements in geometrical measurements.

Abstract: In an exemplary apparatus implementation, an electromagnetic lens includes: an input section including multiple input probes and a curvilinear input reflector; an output section including multiple output probes and a curvilinear output reflector; and a coupling section including a coupling slot and a curvilinear coupling wall. In another exemplary apparatus implementation, an electromagnetic lens includes: a first layer; a second layer adjacent to the first layer; the second layer including multiple input probes, a curvilinear input reflector, and a first curvilinear coupling wall; a third layer adjacent to the second layer, the third layer including a coupling slot; a fourth layer adjacent to the third layer; the fourth layer including multiple output probes, a curvilinear output reflector, and a second curvilinear coupling wall; and a fifth layer adjacent to the fourth layer.

Abstract: A device for receiving/transmitting electromagnetic signals from/to at least two satellites fixedly located at points at the geostationary path comprises an antenna, for example a lens (1) of waveguide nature. The antenna images remote points at a focal surface and in the points where the satellites are imaged receiver horns (23, 23?) are placed. The horns are adjustably mounted to a rail (21) of a mounting unit (9) except the central horn (23?) that is fixedly placed for receiving along the optical axis of the antenna, at a predetermined distance of the antenna. The rail is mounted to be rotated about the optical axis of the antenna, this giving a simple adjustment of the other horns (23). Using an adjusting assembly the curvature of the rail can be varied to be adapted to receiving at different latitudes.

Abstract: In a satellite receiver a feeder element is provided that includes several feeder horns on a microwave head (low noise block downconverter (LNB)) for distributing satellite signals from different satellites to different channels in the different horns and means for blocking all channels, except for the one that is presently desired to be used, before the signals sent on these channels reach the microwave head.

Abstract: An arrangement for feeding a centrally focused reflector antenna includes a waveguide (1), a dielectric field transformer (2) arranged on the waveguide (1) and a mounting platform (3) for a series of modules (8) which is embodied on one end of the waveguide (1). The waveguide (1) is provided with an arrangement for receiving the dielectric field transformer (2) which partially protrudes into the waveguide (1). Preferably, a dielectric support (9) may be provided in the vicinity of the dielectric field transformer (2). The middle of the support has a circular bore (12) whose diameter corresponds to the diameter of the dielectric field transformer (2). The centrally focused reflector antenna can be excited in the focal point thereof in a field-optimum broadband manner.

Abstract: The septum is extended through the opening to the radio wave receiving portion to separate respective polarized waves received by a pair of radio wave receiving portions, and a space between the septum and the radio wave receiving portion is set such that an end surface of the waveguide on the side of the substrate is surely in contact with a grounding surface provided on one surface of the substrate, and an end surface of the radio wave reflecting portion on the side of the substrate is surely in contact with the grounding surface provided on the other surface of the substrate.

Abstract: A device for receiving/transmitting electromagnetic signals from/to at least two satellites fixedly located at points at the geostationary path comprises an antenna, for example a lens (1) of waveguide nature. The antenna images remote points at a focal surface and in the points where the satellites are imaged receiver horns (23, 23′) are placed. The horns are adjustably mounted to a rail (21) of a mounting unit (9) except the central horn (23′) that is fixedly placed for receiving along the optical axis of the antenna, at a predetermined distance of the antenna. The rail is mounted to be rotated about the optical axis of the antenna, this giving a simple adjustment of the other horns (23). Using an adjusting assembly the curvature of the rail can be varied to be adapted to receiving at different latitudes.

Abstract: An antenna (10) having an emitter element which is positioned in front of a conductive reflector (13) and has a three-dimensional cast part. The cast part is implemented as conductive and has a closed peripheral structure (11) having alternating constrictions and bulges. The peripheral structure (11) spans an imaginary surface (14) which is intersected by at least two planes of symmetry (15.1, 15.3) of the cast part. At least two fastening elements (12.1, 12.2) are provided, which extend essentially perpendicular to the imaginary surface (14) and support the peripheral structure (11) at two points which lie on one of the planes of symmetry (15.1; 15.3). At the lower ends (16), the fastening elements (12.1, 12.2) are connected to the reflector (13), the fastening elements (12.1, 12.2) also being used for electrical excitation of the emitter element.

Abstract: The invention relates to a arrangement for feeding a centrally focused reflector antenna, comprising a waveguide (1), a dielectric field transformer (2) arranged on said waveguide (1) and a mounting platform (3) for a series of modules (8) which is embodied on one end of the waveguide (1) The waveguide (1) is provided with a means for receiving the dielectric field transformer (2) which partially protrudes into the waveguide (1). In a preferred embodiment, a dielectric support (9) is provided in the vicinity of the dielectric field transformer (2). The middle of said support has a circular bore (12) whose diameter corresponds to the diameter of the dielectric fields transformer (2). One advantage of the invention is that the centrally focused reflector antennae can be excited in the focal point thereof in a field-optimum broadband manner. No mechanically displaced components are required as a result of the dielectric fields transformer.

Abstract: A system and method for a center fed reflector feed for a parabolic antenna where the feed is configured to include an output portion that is curved in two directions to thereby enhance the E and H plane patterns of the signal directed rearwardly towards a parabolic reflector.

Abstract: A system and method for a center fed reflector feed for a parabolic antenna where the feed is configured to include an output portion that is curved in two directions to thereby enhance the E and H plane patterns of the signal directed rearwardly towards a parabolic reflector.

Abstract: An approach for providing a multiple-beam antenna system for receiving and transmitting electromagnetic signals from a plurality of closely spaced satellites is disclosed. Dielectric inserts are selectively coupled to the feedhorn bodies to alter the radiation patterns according to dielectric constants of the dielectric inserts. A reflector produces multiple antenna beams based upon the altered radiation patterns of the feedhorn bodies. The antenna provides simultaneous transmissions to satellites that are spaced about 2° or less.

Abstract: In an antenna system for transmitting and receiving, in association with a radio device, electromagnetic radiation has an E-field component and an H-field component. The electromagnetic radiation corresponds to a radio frequency power signal having a current and a voltage at a radio frequency. The antenna system includes a first radiating element and a second radiating element, each comprising a conductive material. The second radiating element is spaced apart from, and in alignment with, the first radiating element. A phasing and matching network is in electrical communication with the first radiating element, the second radiating element and the radio device. The phasing and matching network aligns the relative phase between the current and the voltage of the radio frequency power signal so that the H-field component of the corresponding electromagnetic signal is nominally in time phase with the E-field component.

Abstract: A satellite broadcast system and method, particularly useful for television signals, allows for local as well as nationwide broadcast service by allocating greater satellite resources to the more important local service areas. This is accomplished by broadcasting a non-uniform pattern of local service beams and designing the system to establish different service area priorities through factors such as the individual beam powers, sizes, roll-off characteristics and peak-to-edge power differentials. Frequency reuse is enhanced by permitting a certain degree of cross-beam interference, with lower levels of interference established for the more important service areas.

Abstract: A conductive-transmission-line waveguide converter comprising a waveguide for transmitting an electromagnetic wave, a wiring board brought into contact with a side of the waveguide opposite to a side of the waveguide for inputting an electromagnetic wave, being oriented perpendicularly to a longitudinal axis of the waveguide, a first probe provided in an area on the wiring board inside the waveguide for taking in a first linearly polarized wave, and a second probe provided in an area on the wiring board inside the waveguide for taking in a second linearly polarized wave perpendicular to the first linearly polarized wave, wherein the first probe and the second probe are respectively created along mutually perpendicular first and second axis lines, which both pass through a cross point of the wiring board and the longitudinal axis of the waveguide, and a first center line passing through the middle of each transversal line segment of the first probe is shifted from the first axis line and a second center line p

Abstract: When a converter 14 is rotated via a rotation mechanism 17, the arrangement inclination angle of two primary radiators 15a and 15b can be adjusted in the range of 0 to 20 deg. with respect to an axis which is in parallel with the ground. Also the reception polarization angle due to probes of the primary radiators 15a and 15b can be adjusted in the range of 0 to 20 deg. while maintaining a preset difference in polarization angle among the satellites. Therefore, the arrangement inclination angle of the primary radiators 15a and 15b for respectively receiving signals from the two satellites, and the reception polarization angle in the primary radiators 15a and 15b can be simultaneously easily adjusted by rotating the converter 14 via the rotation mechanism 17.

Abstract: A locking assembly is provided with a mounting ring having at least one notch and at least one groove having an entrance adjacent to the notch. A locking ring of the assembly has at least one protrusion disposed in the notch of the mounting ring. A retaining ring holds the locking ring and the mounting ring together. The locking ring is normally biased toward a first, locking position in which the protrusion blocks the entrance of the groove and is moveable to a second, engagement position in which the protrusion is urged against the mounting ring to expose the entrance of the groove. The locking assembly is suitable for engaging and locking various devices having at least one tab, such as an RF feed of an antenna system.

Abstract: The present invention relates to the field of arrangements in reflector antennas, and in particular to that part of this field that concerns reflector antennas that include subreflectors. The invention is concerned chiefly with an improved subreflector (5b) which when used in a reflector antenna (1) enables the antenna to obtain a radiation diagram with high suppression of side lobes in both the H-plane and the E-plane. The reflective structure of the subreflector (5b) includes at least two mutually different geometries (15, 17) that have been configured specifically to obtain radiation diagrams with good suppression of side lobes in both the E-plane and the H-plane.

Abstract: A horn antenna is provided which is capable of operating at a plurality of separate frequencies while providing substantially equalized E and H-plane patterns for each of the separate frequencies. The antenna includes a coupling portion to permit coupling to a communication device. An inner portion is coupled to the coupling portion, and includes a first choke having a depth which extends substantially parallel to a central longitudinal axis of the antenna and a width which extends in a radial direction of the antenna. The depth and the width of the first choke are set so that the first choke will operate at the first frequency. An outer portion is coupled to the inner portion, wherein the outer portion has a maximum diameter in the radial direction which is greater than the maximum diameter in the radial direction of the inner portion.

Abstract: A bifocal lens for use in a multiple beam antenna system including a reflector that is at least partially parabolic in one dimension and a pair of waveguides. Multiple received beams are received and reflected by the reflector into an orthogonal mode junction which separates signals of a first polarity from signals of a second orthogonal polarity. The signals of the first polarity are forwarded into a first waveguide and the orthogonal signals of the second polarity are forwarded into a second parallel waveguide. A plurality of satellites may be accessed simultaneously thus allowing the user to utilize both signals at the same time. The bifocal lenses may be located in the waveguides, respectively, with each lens including a step portion defined in at least one edge thereof for matching purposes.

Abstract: A multiple beam antenna system including a reflector that is at least partially parabolic in one dimension, a pair of dielectric lenses (or optionally at least one shaped reflector to perform functionality otherwise performed by the lens(es)), and a pair of waveguides. Multiple received beams are received and reflected by the reflector into an orthogonal mode junction which separates signals of a first polarity from signals of a second orthogonal polarity. The signals of the first polarity are forwarded into a first waveguide and the orthogonal signals of the second polarity are forwarded into a second parallel waveguide. A plurality of satellites may be accessed simultaneously thus allowing the user to utilize both signals at the same time. In certain embodiments, each of the dielectric lenses may be of the bifocal type.

Abstract: A polarizer for exciting the parabolic reflector of a directional antenna includes a profile section (7) which is formed as a waveguide and is adapted to simultaneously transmit two linearly polarized orthogonal electromagnetic waves. Two rectangular waveguides which separately guide the two electromagnetic waves are connected to the profile section (7). The end face of one of the rectangular waveguides is connected to the side wall of the profile section (7) in a radial direction, whereas the other rectangular waveguide is connected to an end face of the profile section (7). Both rectangular waveguides have an electromagnetic connection to the profile section (7) via openings, wherein a short-circuiting element (10) is disposed in the profile section (7) between the openings.

Abstract: A parabolic rectangular horn antenna includes a source aperture, a parabolic reflector, and an output aperture. The source aperture has a first port for receiving a planar wavefront signal and a second port for providing a substantially cylindrical wavefront signal. The parabolic reflector is positioned within the horn to receive the cylindrical wavefront signal, transforming it to a substantially planar wavefront signal at a predefined location. The output aperture is positioned at the predefined location and outputs the substantially planar wavefront signal. Corrugations are adjacently placed at both sides of the output aperture to optimize the antenna beam pattern.

Abstract: When a converter 14 is rotated via a rotation mechanism 17, the arrangement inclination angle of two primary radiators 15a and 15b can be adjusted in the range of 0 to 20 deg. with respect to an axis which is in parallel with the ground. Also the reception polarization angle due to probes of the primary radiators 15a and 15b can be adjusted in the range of 0 to 20 deg. while maintaining a preset difference in polarization angle among the satellites. Therefore, the arrangement inclination angle of the primary radiators 15a and 15b for respectively receiving signals from the two satellites, and the reception polarization angle in the primary radiators 15a and 15b can be simultaneously easily adjusted by rotating the converter 14 via the rotation mechanism 17.

Abstract: According to the present invention, there is provided a satellite broadcast receiving converter which comprises a waveguide in which the broadcast wave travelling therein travels as a first TE11 mode linearly polarized wave and as a second TE mode linearly polarized wave intersecting at a right angle with each other, a first probe disposed at a predetermined position within this waveguide for detecting the first linearly polarized wave, a first reflecting conductor disposed approximately 1/4 of the wavelength separate from the first probe in the direction in which the electric wave travels for reflecting the first linearly polarized wave, a second probe disposed in the neighborhood of the first reflecting conductor for detecting the second linearly polarized wave, and a second reflecting conductor disposed approximately 1/4 of the wavelength from the second probe in the direction in which the electric wave travels for reflecting the second linearly polarized wave.

Abstract: An antenna (10) having a plurality of stripline antennas (12). Each stripline antenna (12) is comprised of a plurality of radiating elements (14). The plurality of stripline antennas (12) are arranged in a flat array. The shape of each radiating element (14) is prescribed by an exact mathematical expression whose dimensions are a function of the radiating wave length, characteristics of the directional pattern and the input resistance of the antenna (10). Electromagnetic energy is supplied via a rectangular waveguide (40) and arrives at the input ends of the stripline antennas (12) via an excitation device (20), a gradual junction (28) and a radial bend (30).

Abstract: A circularly polarized generator for transmitting circularly polarized transmitted electromagnetic waves and a circularly polarized wave reception antenna for receiving the electromagnetic waves is disclosed. A crank-shaped conductor pattern composed of a pair of U-shaped portions connected to each other so that the open sides of the letter U are directed oppositely to each other is affixed on a substrate, and has its one end arranged as a signal transmitting and receiving end for achieving minimum transmission losses and optimum axial ratio or intersecting polarized wave component discriminating factor as well as for reducing the size and weight and assuring ease of manufacture.

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

Abstract: 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.