Showing papers on "Feed horn published in 1983"

Low side lobe gregorian antenna

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

An offset dual-reflector antenna shaped from near-field measurements of the feed horn: Theoretical calculations and measurements

Abstract: A synthesizing procedure for shaping dual-reflector offset antennas is described. The synthesis is based on geometrical optics and near-field measurements of amplitude and phase from the feed element. The procedure preserves good symmetry in mapping from feed to aperture which results in minimal distortions of the electrical characteristics of the antenna. A 1.8 m antenna has been manufactured and measured at 12 GHz. The radiation pattern is characterized by low sidelobes and cross polarization introduced by the offset geometry below -50 dB.

Aperture transformation sidelobe canceller

Abstract: An aperture transformation sidelobe canceller includes a plurality of auxiliary feed elements disposed in the vicinity of, but critically offset from, a main feed horn. The signal paths for the auxiliary feed horns are coupled through a low loss cascade RF variable direction coupler network to be combined with the RF signal path for the main antenna feed. The combined signal path is coupled to a performance monitoring processor which, in turn, adjusts the coupling action of each variable directional coupler to achieve the necessary weighting and combining of the auxiliary feed signal paths. The critically offset auxiliary feed elements provide the capability of achieving very broadband and deep nulls from the simple variable directional coupler network. The null availability makes it possible to null the entirety of the main elements sidelobe region, including backlobe and even the first sidelobe region of the antenna pattern, as the offset auxiliary feed horns provide substantial coverage in this region. These offset auxiliary feed elements provide low differential dispersion, require reduced waveguide runs, enjoy polarization diversity by slightly depolarizing and rotating each feed and suffer essentially no grating problems.

Cylindrical and three-dimensional corner reflector antennas

Abstract: Two reflector antennas are proposed. The first is constructed by adding a cylindrical reflecting surface of suitable radius to the V -shaped corner reflector antenna. The feeding element is a half-wavelength dipole. The resulting cylindrical corner reflector provided a 2 dB increase in gain, minimum sidelobe level, low input reactance, and uncritical dependence of performance on frequency. The second antenna is constructed by adding a cylindrical surface to the three-dimensional corner reflector. This extension provided an increase in gain of at least 6.5 dB, an input resistance compatible with the commercially available 50- or 75-\Omega coaxial cables, low input reactance, and uncritical dependence of performance on frequency. A grid-type cylindrical corner reflector antenna, and a three-dimensional corner reflector antenna with a cylindrical subsurface of finite reflecting surfaces were designed, and the measured input impedances, gains, and field patterns showed excellent agreement with the theoretical results for both antennas.

Defocusing loss for a long periodic-fed reflector

Abstract: Log periodic designs are a well established wide-band antenna technology, but one in which the phase center travels along the structure as the frequency varies. When a log periodic antenna is used as a feed for a reflector antenna, the phase center location cannot be maintained at the reflector focus over the frequency range and defocusing results. The purpose of this analysis is to quantify the defocusing loss for a log periodicfed reflector. The analysis presented compares favorably with measured results.

Dual polarized feed with feed horn

Abstract: The present invention relates to a dual polarized feed by which two linearly polarized waves can be reliably separated. The two waves are conducted separately over high frequency coaxial cables, one of which extends axially and the other radially into the polarizer. Rotation of the planes of polarization is thus unnecessary and the two cables have a minimum influence on the illumination (irradiation) of the reflector.

Antenna with feed horn and polarization feed

Abstract: A polarization feed is provided for use in a directional antenna under separation of two linearly polarized electromagnetic waves whereby the feed is basically comprised of a tube, one end of which flares into a feed horn configuration and two wave guides are connected thereto, one ending laterally with its axial end at the feed tube while the other one has one side connected to the other axial end of the feed tube under consideration that respective long cross sectional dimensions are 90° rotated with respect to each other as connected to the tube. Appropriate means are provided for obtaining low reflection feeding.

Waveguide structure for separating microwaves with mutually orthogonal planes of polarization

Abstract: A waveguide structure carrying microwaves with two mutually orthogonal planes of polarization and in two different frequency bands, transmitted and received by an associated antenna, comprises two orthomode transducers in the form of coaxial cylindrical guide members of different inner diameters, the smaller-diameter transducer terminating in a short-circuiting end wall while the larger-diameter transducer, adjoining same at an annular shoulder, extends to a feed horn confronting a reflector. Each transducer is formed with two elongate peripheral access slots, opening onto respective rectangular-section branches, which are longitudinally bisected by mutually perpendicular axial planes while being relatively offset in axial direction. Each slot of the larger-diameter transducer is partly traversed by two pairs of conductive dividers, at locations spaced from its ends by about a quarter of the slot length and of a height equal to about a third of the slot width, serving to suppress the propagation of higher modes of higher-frequency waves in the respective branch guides.

Frequency sharing antenna

Abstract: PURPOSE:To obtain the equivalent efficiency among antennas with use of each exclusive primary antenna by piercing a horn antenna through the area at the center of a print antenna where no radiating element is formed. CONSTITUTION:For higher frequencies, a primary reflector 1 is irradiated by a horn 9 for high frequencies which is piercing through a hole drilled at the center part of a print antenna 13 where no irradiating element 16 is formed. Then the reflector 1 reflects two radio waves of high and low frequencies radiated from the antenna 13 to the spaces along radio wave routes 7 and 7' respectively.

Focal finder for parabolic reflector antenna

Abstract: A compact, easily manipulable measuring device is provided, particularly useful for properly positioning the feed horn of a parabolic reflector antenna, or the like, relative to the satellite reflecting dish of the antenna. When installing or maintaining an antenna, it is important for optimum signal reception to position the feed horn at or near the focal point of the satellite dish. Such feed horns typically present a central axis, which if aligned with the center point of the satellite dish approximately positions the feed horn at the focal point of the satellite dish. The device of the present invention presents a telescopic rod structure coupled to a support head. The support head presents structure for attachment to the feed horn such that the rod structure preferably lies along the feed horn central axis. With the rod structure extended to a position adjacent the satellite dish, it is readily apparent whether the feed horn central axis is aligned with the satellite dish center point or if adjustment of the feed horn is necessary.

Optical sensor and reflector to reflect a different wavelength

Abstract: An optical sensor is disclosed comprising a transmitter which transmits a light beam, a receiver 2 for receiving reflected light and a reflector for directing light from the transmitter to the receiver. The reflector converts the wavelength of the light transmitted by the transmitter and the receiver is tuned to detect light of the converted wavelength. Objects located in the area between the reflector and the combination transmitter/receiver are detected as they do not convert the wavelength of the light from the transmitter even if they reflect light to the receiver.

Beam waveguide feeder

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

A K/C/S bands satellite antenna with frequency selective surface

Abstract: A K(30/20 CHz)/C(6/4 GHz)/S(2.6/2.5 GHz) bands offset satellite antenna with an S/C bands feed horn and a low pass frequency selective surface (FSS) covering only part of a whole aperture angle, is designed, reproduced, its characteristic as an onboard antenna is confirmed and a design method and characteristic evaluation method for this type of antenna are established. In this antenna, three different frequency bands with different optimum aperture diameters share one reflector. the optimum aperture diameters peculiar for respective frequency bands (1.8 m for S, 1 m for C, K bands) are realized equivalently by choosing the diameter of the S/C bands feed horn and the size of FSS. the decrease in service area edge gain due to frequency bands sharing is about 1 dB, a satisfactory result compared to the case in which respective frequency band antennas are on board. the efficient analysis method assuming equivalent currents on the plane containing the FSS is derived to evaluate scattering from the small FSS. This method permits an antenna design with FSS size as a parameter; this was not considered before. the design and analysis of the antenna are confirmed by measurements.

Dual-Depth Corrugated Horn Design

Abstract: The dual-depth corrugated horn gives low cross-polarisation at two separate operating frequencies A space harmonic formulation has been used to study the influence of the corrugation geometry on the cross-polarisation characteristics Results show that about seven slots per wavelength are needed for low cross-polarisation and that operation with frequency bands separated by two to one is practical

Symmetrical crossed rectangular horn for a circularly polarized multiple-beam reflector antenna

Abstract: Radiation characteristics of a symmetrical crossed rectangular horn using a solution of an integral eigenvalue equation given by Lin is described. E - and H -plane pattern symmetry and two-dimensional radiation patterns for circular polarization are studied comparing with those of a square horn, with specific emphasis on cross-polarization levels. Using a symmetrical crossed rectangular horn as a circularly polarized primary feed gain and cross-polarization characteristics of offset paraboloidal reflector antennas with circular and elliptical apertures have been investigated. A practical example of a circularly polarized multiple-beam antenna with contoured pattern using three symmetrical-crossed rectangular horns is shown.

Beam forming networks for mm-wave satellite communications

Abstract: Technology features of a beam forming network (BFN) employing ferrite devices to provide multiple beam antenna pattern control for satellites used in telecommunications are described. The BFN produces the phase and amplitude distribution for each horn in an antenna array, with the number of horns in the array being equal to the number of outputs in the BFN. One configuration involves microwave switches and permits illumination of a single feed horn at a time using ferrite latching circulators that function by reversing the circulation direction. A more flexible version, yielding a variable amplitude distribution across the feed horn array to accommodate changing traffic patterns or serving a TDMA system, includes the capability of forming nulls in the system with a variable phase shifter in the input ports. The antenna scan angles in phased arrays can be limited to 8 deg from center. Acceptable insertion losses have been demonstrated in BFN with hundreds of ports and switching rates as high as 10 kHz.

An antenna, particularly for the reception of satellite communications

Abstract: A groundstation antenna comprises a body 1 of a foamed plastics material having on a rear parabolic surface a metallised coating (3) providing a main reflecting surface. A front surface of the body (1) has on a hyperbolic surface a metallised coating (2) providing a sub-reflector. A feed horn is received within a rear recess (4) in the body 1. The main reflector and the sub reflector are thus accurately located with respect to one another and protected from the weather. In an alternative embodiment (Figure 7), two casing members are joined at their outer peripheries to form an antenna of enclosed, hollow shell-like form.

Polarisation filter with feedhorn

Abstract: A polarization feed is provided for use in a directional antenna under separation of two linearly polarized electromagnetic waves whereby the feed is basically comprised of a tube, one end of which flares into a feed horn configuration and two wave guides are connected thereto, one ending laterally with its axial end at the feed tube while the other one has one side connected to the other axial end of the feed tube under consideration that respective long cross sectional dimensions are 90 DEG rotated with respect to each other as connected to the tube. Appropriate means are provided for obtaining low reflection feeding.

An experimental broadband imaging feed

Abstract: Imaging with Fresnel diffraction taken into account is applied to the design of a broadband narrow pattern feed. This feed is not only a basic building block of an imaging beam waveguide, but also essential for an offset reflector antenna of large effective F/D ratio. Furthermore, it can be used as a constant beamwidth radiometer antenna for multifrequency remote sensing. We have built and tested a practical example that consists of an offset ellipsoidal reflector and a corrugated horn. Measured amplitude and phase patterns agree with calculated results, which include truncation effects. Systematic design procedures are obtained for a given feed horn and the required reflector illumination. Necessary and sufficient conditions of the thin lens model are translated into design parameters of an offset ellipsoidal reflector with projected circular aperture. Geometrical relations of the offset ellipsoid and calculations of radiation patterns are described in the appendices.

Reduction of sidelobe level of reflector antennas by covering feed struts with a periodic structure

Abstract: A periodic structure has been investigated and optimised which can be used to cover the struts of reflector antennas in order to reduce the far sidelobes caused by scattering from the struts.

Beam feeding device

Abstract: PURPOSE:To eliminate the inconvenience that is due to with use of a spherical mirror antenna, by providing such a constitution that an equivalent feed horn can move in an optional direction at an optional position while a feed horn is fixed. CONSTITUTION:The electric wave radiated from a feed horn 1 is reflected by reflectors 20 and 21 and a planer reflector 22 and then focused temporarily at a point 36. The electric wave focused at the point 36 is reflected again by reflectors 23 and 24 and a planer reflector 25 and focused at a point 37. Thus the electric wave is transmitted to an antenna as if the electric wave were radiated from an equivalent horn 1'. The reflectors 20, 21 and 22 as well as 23, 24 and 25 all have a rotary shift centering on the center optical axis of the horn 1, i.e. a rotary axis 18. At the same time, the reflectors 23, 24 and 25 turn round an axis 19. In general the rotations round axes 18 and 19 and the expansion/ contraction toward axis 40 have a movement of a polar coordinate system with an axis Z defined as a zenith axis to produce three independent variables. Therefore a point 35 can be shifted to an optional position.

Compact Phased Array Fed Dual Reflector Antenna System

Abstract: : A compact phased array fed dual reflector antenna system. The antenna system includes a parabolic main reflector, an elliptical sub-reflector, and a phased feed array. The focal point of the parabolic main reflector is located on the elliptical surface of the sub-reflector. A first elliptical focal point of the sub-reflector is located on the parabolic surface of the main reflector while the second elliptical focal point is located on the radiating surface of the feed array.

Offset-fed parabolic reflector antenna with low cross-polarisation

Abstract: The object is to reduce the cross-polarisation component of a microwave antenna with an offset-fed parabolic cup as the main reflector. A feed system is provided for this purpose which generates the radiation of a Huygens' source. In this way, the feed system is dimensioned and aligned on the parabolic cup such that the radiation field is converted into a planar field after reflection on the cup.

Primary-focus operation of shaped dual-reflector antennas

Abstract: Primary-focus operation of reflectors designed for optimum performance in a shaped dual-reflector configuration is considered. Provided the reflector diameter is , only a small loss in efficiency is suffered in comparison with a paraboloidal antenna.

Primary and Secondary Patterns From Array-Fed Off-Set Reflector Antennas

Abstract: The paper describes how mutual coupling influenees both the primary and secondary radiation patterns of array-fed off-set reflector antennas. The principle cause of adverse crosspolarisation is attributed to coupling between the TE11 and TE21 modes in the array. This then is the main cause of crosspolarisation in an optimised dual reflector. It is shown that coupling to the TE21 mode can be minimised with the correct choice of horn.

A Two Channel Receiver at 22 GHz for Holographic Measurement of Reflector Antenna Profiles

Abstract: This paper reports a two channel, coherent holography receiver for the measurement of the two dimensional reflector profile of the 30 m millimeter radio telescope at Pico Veleta, Spain. Using a phase and frequency locked Gunn oscillator as local oscillator, a path length difference of 30 ?m can be measured.

An offset bifocal dual reflector antenna

Abstract: An offset bifocal dual reflector antenna is described. The technique for generation of discrete points on both the subreflector and main reflector surfaces is discussed and a phase error analysis is presented as well.