Showing papers on "Feed horn published in 1982"

Asymptotic analysis of parabolic reflector antennas

Abstract: Dual mode horns employed commonly as feeds for parabolic reflector antennas generate a radiation pattern that can be well-approximated by a Gaussian beam. To determine the far field of the antenna, it has been customary to perform integrations either of the physical optics currents on the reflector surfaces or of the ray optically determined field in the antenna aperture. These time-consuming integrations may be avoided if the Gaussian beam is tracked directly from the feed horn via subreflectors, if any, to the main reflector and then to the far zone. The tracking of such fields may be accomplished either by the complex-source point method or, in principle, by evanescent wave tracking. The former utilizes a complex coordinate space while the latter tracks fields entirely in the physical (real) coordinate space. For a parabolic antenna with an offset beam feed centered at the focus, both methods are examined here and an assessment is made of how the one can best complement the other. Numerical comparisons with results deduced elsewhere by a semi-heuristic procedure, and with experimental data, reveal the accuracy and versatility of the complex ray procedure.

Reflector-type microwave antennas with absorber lined conical feed

Abstract: A feed horn for a reflector-type microwave antenna comprises a smooth-walled conical horn and a lining of absorber material on the inside wall of the horn for reducing the width of the RPE (radiation pattern envelope) in the E plane of the antenna. The lining of absorber material extends from the wide end of the conical feed toward the narrow end thereof, terminating at a point where the horn diameter is about 7 times the longest wavelength of the microwave signals being transmitted. The width of the RPE in the E-plane of the antenna can be reduced to be nearly equal to the width of the RPE of the H-plane of the antenna without significantly degrading this H-plane RPE from its shape without absorber and without significantly changing the gain of the antenna.

A transform technique for computing the radiation pattern of prime-focal and Cassegrainian reflector antennas

Abstract: An efficient numerical method based on the use of the fast Fourier transform (FFT) algorithm is developed for computing radiation patterns of aperture antennas with given aperture distributions. The method is also readily applicable to the problem of computing the radiation pattern of paraboloidal reflector antennas when the induced surface currents on the surface of the reflector are known. Using an efficient launching and scanning scheme for subreflector analysis, the method is extended to a Cassegrainian reflector antenna system.

Corrugated antenna feed horn with means for radiation pattern control

Abstract: A horn feed for use with a reflector for generating a narrow beam of radiated energy in a radar system. The horn includes surface corrugations and provides a unique configuration of horn flare angle, length of the corrugation pattern along the horn inside surface in the direction of radiation and the cross-sectional dimension of the horn at the beginning of the corrugation pattern, for the minimization of sidelobe generation and optimum illumination of the reflector.

Diagonal-conical horn-reflector antenna

Abstract: A horn-reflector microwave antenna has a reflector plate which is a section of a paraboloid, and a flared feed horn for supplying microwave signals to the reflector plate The horn has a conical section forming a circular aperture at the wide end, which is the end closer to the reflector plate, and a pyramidal section forming a square aperture at the narrow end, which is the end farther away from the reflector plate Microwave signals are supplied to the feed horn with the electrical field extending along a diagonal of the square aperture

Flanged parabolic antennas

Abstract: The radiation characteristics of symmetric parabolic antennas with a peripherical flange are examined in detail in order to assess the effectiveness of such a flange in reducing the backward scattered field. It is shown that the best behavior is obtained by using a right-angled flange, which allows achievement af a significant field level reduction in a wide rear angular sector, without affecting the field radiated in the forward directions.

Offset microwave feed horn for producing focused beam having reduced sidelobe radiation

Abstract: A short-focus microwave reflector is located a short distance away from the feed horn and is positioned to reflect the beam of microwave radiation away from the feed axis and toward a large primary reflector antenna for transmission. A conical shield extends from the feed horn to the secondary reflector, joining them together as a unit and preventing sidelobe radiation. The beam of radiation emerges from the shield through an aperture in the sidewall thereof. The short focus of the secondary reflector causes the beam to be focussed approximately at the plane of the aperture, such that the beam diameter is small and the aperture can also be small, reducing stray radiation from the shield structure. Diffraction at the edges of the aperture is reduced by a radially surrounding choke structure which further suppresses sidelobe radiation.

Analysis of a new corrugated guide feed horn having dual‐depth corrugations

Abstract: A new corrugated guide horn having dual-depth corrugations was proposed by Carpenter and Ghosh in 1980. It is attractive for achieving improved performance over a wide band or a multiband. In this paper a space-harmonic analysis has been made, the relation between the fields in the adjacent slots of the dual-depth corrugations has been found, and the eigenvalue equation and the formulae of the equivalent admittance have been established. As an example, the predicted performances of a new multiband horn have been given.

Antenna device for air traffic radar

Abstract: Disclosed is an antenna device, which comprises a reflector and a primary radiator for an ARSR system including a low beam horn antenna disposed at a position substantially at the focal point of the reflector and a high beam horn antenna disposed below the low beam horn antenna. The antenna device further comprises a primary radiator for an SSR system including two modified diagonal horns provided on opposite sides of and having outside perimeters complementary to the arrangement of the low and high beam horn antennas and at positions corresponding to a position midway between the low and high beam horn antennas. A Yagi antenna used as a part of the SSR radiator, is disposed above the low beam horn antenna. Thus, the antenna device can be used commonly for both the ARSR and SSR systems.

Beam scanning and focal surfaces for parabolic cylinder reflectors

Abstract: The location of the focal surfaces for parabolic cylinder reflectors with Gaussian tapered illumination is investigated and compared with that obtained by numerical simulation. It is found that an idealized surface that holds approximately in most practical cases is the circle described on the vertex-focus line as diameter. Formulas are derived for the change of gain and beamwidth with scan angle.

Bandwidth capabilities of array-fed parabolic cylinders

Abstract: The bandwidth of hybrid phased-array/reflector antennas, in which a large parabolic cylinder reflector is fed by a relatively small phased array, is investigated. Two types of array feeds are considered: one employs only phase-amplitude matching, the other employs amplitude and time-delay matching. In the case of phase-amplitude matching, the on-axis hybrid array/reflector designs are shown to have substantially higher bandwidth than pure phased arrays. A form of time-delay compensation is described which removes the bandwidth limitations of hybrid array/reflectors, but introduces interfering signals. This interference can be avoided by either locating the feed outside the caustic zone or by using off-axis array feeds.

Maximum Power Transmission in Mass-Limited Radio Systems

Abstract: A simple fundamental relationship is derived between antenna gain and transmitter power which maximizes the effective radiated power in mass-limited satellite systems. In the most common case, maximum effective radiated power is achieved when the payload mass is divided equally between the antenna system and the power system. Although this may have been known intuitively to satellite designers, to the author's knowledge this relationship has never been published. Example calculations show that considerable increases in performance can be expected for satellites which employ high-gain multibeam antennas.

Design considerations for millimetre wave lens antennas

Abstract: The operational background and some of the possible single and dual lens antenna options for use in a millimetric sensor with approximately 3° beamwidth have been examined. A particular single lens antenna design gave a scan of more than ±3 beamwidths and compatibility with conical scan, beam broadening and monopulse operation.A dual lens antenna design was operated both with a single feed horn and with a rectangular matrix of plain waveguide radiators (with potential application in real time imaging). Good scan characteristics were obtained out to ±6 beamwidths with the single feed horn but the matrix feed assembly needed a group of elements to be fed in phase before equivalent performance could be obtained. The aim of the work was to simulate feeding the lens antenna with a monolithic array and whilst an array of waveguides can not accurately model all the properties of a monolithic array they are considered sufficiently representative to indicate some of the compromises that may have to be made.

Axially symmetric radiation patterns from flanged E-plane sectoral horn feeds

Abstract: A simple technique for obtaining identical F and 11-plane patterns from E-plane sectoral feed horn is presented Halfpower beam width and gain of the antenna are also improved considerably Experimental resultsfor a number of horns with flanges of various parametersare also presented This system may find practical application in radar andspace communication systems

Horn-reflector microwave antenna with internal debris trap

Abstract: A horn-reflector microwave antenna comprises the combination of a paraboloidal reflector for transmitting and receiving microwave signals; a tapered feed horn extending downwardly from the reflector for guiding microwave signals to and from the reflector; a waveguide connected to the lower end of the feed horn; and a dielectric membrane extending across the interior of the feed horn for collecting any debris that falls down into the feed horn. In the preferred embodiment of the invention, the outer periphery of the dielectric membrane is secured to the interior walls of the feed horn, and the central portion of the membrane is elevated above the periphery thereof so that debris collected on the membrane slides to the walls of the feed horn.

Offset parabolic antenna

Abstract: PURPOSE:To improve gain by composing the titled antenna of a common part for two intersecting polarized waves at right angles which excites a primary radiator by two polarized waves and a single polarized wave part which excites said radiator by one polarized wave. CONSTITUTION:A horn antenna 5 is excited by two circular polarized waves which are intersected at right angles. A horn antenna 6 is excited by a circular polarized wave having right or left revolution. Both horn antennas 5, 6 are arranged on the positions perpendicular to the symmetrical surface of a reflector of an offset parabolic antenna. It is defined that the polarized wave excited only by the horn antenna 5 is a right turning circular polarized wave and the one excited by the horn antennas 5, 6 is a left turning circular polarized wave. Both antennas 5, 6 are arranged in parallel by shifting them from the focus 0 of the reflector so that the peaks of two main beams of intersecting circular polarized waves originated from both horn antennas are made to coincide with each other. Since the peak directions of the main beams of both polarized waves can be made to coincide with each other, the gain is prevented from reduction.

On the accuracy of physical optics

Abstract: The first-order correction to the physical optics (PO) solution for the axial radiation field from parabolic reflector antennas is found. The correction is of order k^{-1} and is in quadrature with the PO solution. By means of the correction term the accuracy of the PO surface integral is round to be better than 0.22(\lambda/D)^{2} dB on axis, where D is the diameter of the reflector. Thus, the PO solution for the directivity is extremely accurate for commun reflector sizes of several wavelengths \lambda .

Exact gain measurement of large aperture antennas using celestial radio sources

Abstract: The correction factors for angular extension of celestial radio sources, Cassiopeia A (Cas A), Taurus A (Tau A), and Cygnus A (Cyg A) were calculated based on the detailed contour maps of brightness temperature. Examinations of the flux densities of those radio sources were made using the published data. The gain of antennas of several sizes measured by using the three radio sources was determined by applying the newly obtained parameters. It was found that the gain of large aperture antennas at 4- and 6-GHz bands could be determined to the accuracy of better than \pm0.45 dB (3\sigma) by use of the three radio sources.

Evolution of Multiple-Beam Antenna Design for Intelsat Satellites

Abstract: An offset reflector antenna fed by a horn array feed is employed by INTELSAT to achieve multiple frequency re-use via spatial and polarization isolation among various coverage beams. As the satellites evolve from INTELSAT-V to INTELSAT-VI, the basic multiple beam antenna configuration remains the same. However, the reflector has to be made larger due to the introduction of more zone coverage beams with closer spacing. In addition, the feed array must be refined to improve its polarization purity and expand its bandwidth; the feed network is also designed to have lower loss and be more compact. For satellites beyond INTELSAT-VI generation. the teehuclogy demand will rely on using even larger reflectors to provide zone beams sep3I'ated very closely. The use of variable power dividers (VPS) and phase shifters (VPS) is very likely when a certain degree of reconfigurability is required. The feed array will require a selection between circular conical horns or multi-mode horns depending on the bandwidth requirement.