Showing papers on "Cassegrain antenna published in 1970"
23 Mar 1970
TL;DR: The complete pattern of a parabolic reflector antenna was calculated using the singly-diffracted rays of the geometrical theory of diffraction, with proper corrections for the forward and real axial directions.
Abstract: : The complete pattern of a parabolic reflector antenna was calculated using the singly-diffracted rays of the geometrical theory of diffraction, with proper corrections for the forward and real axial directions. Excellent agreement with experimental patterns can be expected, if the aperture blockage is not significant. The solution has the usual advantages of a solution based on the geometrical theroy of diffraction, namely, it is obtained in the form of simple functions, its computation cost is low, it is directly related to the radiation mechanism of the antenna and so it can be readily used in the design problem, and it can be easily extended and modified as the need arises.
31 citations
Patent•
20 Feb 1970TL;DR: In this article, a conical or pyramidal horn-radiator having small flare angle changes within the horn at cross-section dimensions much larger than the input waveguide is used to excite higher order modes which control the E-plane aperture distribution and produce a tapered aperture field in the Eplane.
Abstract: A conical or pyramidal horn-radiator having small flare angle changes within the horn at cross-section dimensions much larger than the input waveguide, to excite higher order modes which control the E-plane aperture distribution and produce a tapered aperture field in the E-plane. Equal E- and H-plane beamwidths are thereby obtained. The horn has particular use as a feed for a parabolic reflector, such as a Cassegrain antenna. The flare angle changes are used for pattern improvement in a first frequency band, and separate means are provided for pattern improvement in a second band.
22 citations
TL;DR: An aberration-correcting line source feed has been designed, modeled, constructed, and tested in the Arecibo reflector as mentioned in this paper, achieving an aperture efficiency of 70 percent with a peak gain near 56 dB, half-power beamwidth of 16.2 minutes of arc, and sidelobe levels below 4 percent of the on-axis gain.
Abstract: An aberration-correcting line source feed has been designed, modeled, constructed, and tested in the Arecibo reflector. The feed is a linearly polarized flat wavegnide 40-foot-long array illuminating 700 feet of the 1000-foot-diameter spherical reflector at 318 MHz. The antenna, illuminated by the new feed, yields an aperture efficiency of 70 percent with a peak gain near 56 dB, half-power beamwidth of 16.2 minutes of arc, and sidelobe levels below 4 percent of the on-axis gain. Vignetting losses are approximately 30 percent at the highest zenith angle.
18 citations
01 Sep 1970
TL;DR: In this paper, a simple design procedure was proposed to determine the dimensions of a rectangular flared-horn primary feed, operating in the TE10 mode, for parabolic reflectors, having any f/d ratio and with either a rectangular or circular contour, so that maximum aperture efficiency was obtained.
Abstract: The paper describes the derivation of a simple design procedure by which the dimensions of a rectangular flared-horn primary feed, operating in the TE10 mode, may be determined for parabolic reflectors, having any f/d ratio and with either a rectangular or circular contour, so that maximum aperture efficiency is obtained. The design technique is based on achieving a best match between the principal component of the reflector focal-plane electric field and that electric field existing in the horn mouth during transmission. In addition, the design procedure predicts the value of the spillover power, the reradiated power, the relative edge-field illumination, the resultant reflector aperture-field distribution and the value of the maximum aperture efficiency obtainable for the given combination of horn feed and reflector.
16 citations
Patent•
24 Nov 1970TL;DR: In this paper, two or more main beams of an offset parabolic reflector antenna are directed without producing second order aberrations by placing their respective feeds so that their phase centers reside at mathematically defined locations.
Abstract: In accordance with the disclosure, two or more main beams of an offset parabolic reflector antenna are directed without producing second order aberrations by placing their respective feeds so that their phase centers reside at mathematically defined locations.
13 citations
Patent•
15 Sep 1970
TL;DR: An antenna using a primary horn radiator and at least one reflector, in which a wave absorber is positioned at a limited area of the center portion of the reflector for absorbing electric waves which would otherwise reflect from that limited area and be reapplied to the horn radiator, is described in this paper.
Abstract: An antenna using a primary horn radiator and at least one reflector, in which a wave absorber is positioned at a limited area of the center portion of the reflector, for absorbing electric waves which would otherwise reflect from that limited area and be reapplied to the horn radiator, so that reaction between the feed radiator and the reflector is substantially eliminated.
8 citations
TL;DR: For any paraboloidal reflector operating in a focused condition, the aperture-field orientation can be obtained by first stereographically mapping the feed-polarization pattern and then overlaying the paraboloid aperture on the projection as discussed by the authors.
Abstract: For any paraboloidal reflector operating in a focused condition, the aperture-field orientation may be obtained by first stereographically mapping the feed-polarization pattern and then overlaying the paraboloid aperture on the projection. Examples shown are for electric and magnetic dipoles, and Huygens source feeds pointed at central and offset sections of the paraboloidal reflector.
8 citations
Patent•
27 Apr 1970TL;DR: In this article, the front feedhorn of a parabolic reflector antenna has curved members as the support structure which correspond to a paraboloid of revolution, and the curved members reflect incident radio wave energy into a focal point having absorbent material.
Abstract: A tripod feed support structure for the front feedhorn of parabolic reflector antennas has curved members as the support structure which correspond to a paraboloid of revolution. The curved members reflect incident radio wave energy into a focal point having, for example, absorbent material. The structure substantially eliminates the residual effects of aperture blockage caused by the feed support structure.
7 citations
31 May 1970
TL;DR: In this paper, the authors evaluate large reflector antennas including effects of primary reflector astigmatism and its measurement through diffraction, and show that the effect of the primary reflectors on the measurement of diffraction is negligible.
Abstract: Evaluation of large reflector antennas including effects of primary reflector astigmatism and its measurement through diffraction
5 citations
Patent•
27 Mar 1970
TL;DR: An end-fire antenna having a thick-wall dielectric tube concentrically positioned about the principal axis of a cassegrain antenna and seated on the main reflector functions as a guiding structure for focusing the antenna radiation as discussed by the authors.
Abstract: An end-fire antenna having a thick-wall dielectric tube concentrically positioned about the principal axis of a cassegrain antenna and seated on the main reflector functions as a guiding structure for focusing the antenna radiation.
5 citations
TL;DR: In this article, it was shown that the prime focus-fed equivalent paraboloid is useful only for feeds near the Cassegrainian focus, and the discussion of series expansions of the phase in the system aperture yields severe differences between the CSA system and the prime-focus-fed Paraboloid for larger radial or axial defocusing.
Abstract: In Cassegrain antennas, the whole focusing system is usually replaced by an equivalent paraboloid of focal length mf, where f is the focal length of the paraboloid and m is the magnification of the Cassegrain system. Here, it is shown that this equivalent paraboloid is useful only for feeds near the Cassegrainian focus. The discussion of series expansions of the phase in the system aperture yields severe differences between the Cassegrain system and the prime focus-fed equivalent paraboloid for larger radial or axial defocusing.
TL;DR: Beam switching Cassegrain antenna for millimeter wave radio astronomical measurements, describing RF and electronic systems as mentioned in this paper, was used for the measurement of the Earth's magnetic field. But this antenna was not designed for wireless communications.
Abstract: Beam switching Cassegrain antenna for millimeter wave radio astronomical measurements, describing RF and electronic systems
TL;DR: In this article, the amplitude and phase characteristics of the sum and difference patterns as a function of feed displacement and sum pattern taper were investigated in a parabolic reflector system.
Abstract: An investigation of defocused beam broadening by feed displacement in a parabolic reflector and its potential use as an acquisition means in a monopulse tracking antenna system is presented. The emphasis of the investigation is in the amplitude and phase characteristics of the sum and difference patterns as a function of both feed displacement and sum pattern taper. The investigation, which was performed both analytically and experimentally, shows that when feed defocusing is employed to achieve a beamwidth increase in excess of five times the defocused beamwidth, multiple nulls form in the difference pattern. Since these nulls are positioned relatively close to the beam center, acquisition is still possible under these conditions and the resulting tracking error should be tolerable for most telemetry and communication applications.
01 Sep 1970
TL;DR: In this paper, an expression for the illumination efficiency of a shaped Cassegrain system when the feed pattern differs from a given pattern used for designing the shaped reflector system was derived.
Abstract: Using geometrical optics approximation, an expression is derived for the illumination efficiency of a shaped Cassegrain system when the feed pattern differs from a given pattern used for designing the shaped reflector system.
01 Nov 1970
TL;DR: Unfurlable spacecraft antenna design and electrical characteristics, using Gregorian geometry with conical main and parabolic subreflector, were described in this paper, where the authors used the parabolic reflector as an antenna.
Abstract: Unfurlable spacecraft antenna design and electrical characteristics, using Gregorian geometry with conical main and parabolic subreflector
TL;DR: In this article, a focused aperture antenna was realized using a convex subreflector with a spherical main reflector, and good agreement was obtained between the measured and calculated field in the focal region.
Abstract: A focused aperture antenna has been realised using a (Cassegrain) convex subreflector with a spherical main reflector. The design was based on geometrical optics, and good agreement was obtained between the measured and calculated field in the focal region.
01 Jan 1970
01 Jan 1970
01 Sep 1970
TL;DR: The casaegrain reflector, when fed by a four element array, finds very common usage as an amplitude comparison monopulse system and the boresight sum gain and difference sensitivity essentially determine the range and pointing accuracy of the system as mentioned in this paper.
Abstract: The casaegrain reflector, when fed by a four element array, finds very common usage as an amplitude comparison monopulse system. The boresight sum gain and difference sensitivity essentially determine the range and pointing accuracy of the system. Although much is known about the cassegrain reflector [1] and extensive work has been done on an idealized parabolic reflector monopulse system as a function of feed size and excitation [2], little has been published on the cassegrain monopulse system.
TL;DR: The far field radiation patterns of open cassegrain antennas have been previously computed by a double integration as mentioned in this paper, which has been eliminated by using a modified stationary phase approximation, and the rather remarkable accuracy thus obtained motivated an investigation to estimate the error in this approximation.
Abstract: The far field radiation patterns of open cassegrain antennas have been previously computed by a double integration1. Recently one integration has been eliminated by using a modified stationary phase approximation2. The rather remarkable accuracy thus obtained motivated an investigation to estimate the error in this approximation.