Showing papers on "Parabolic reflector published in 1973"
TL;DR: A thousand kW solar furnace with 63 orientator mirrors, each of 45 m 2 surface, with 180 single mirror panes, was completed in 1970 as mentioned in this paper, where the movement of this installation was guided by electronic controls operated by reflected rays.
74 citations
TL;DR: General formulas are derived for the caustic surface and irradiance over an arbitrary receiver surface for point source radiation on collimated rays that are reflected or refracted by a curved surface.
Abstract: General formulas are derived for the caustic surface and irradiance over an arbitrary receiver surface for point source radiation on collimated rays that are reflected or refracted by a curved surface. Specific formulas are obtained for light from a point source that is deflected by an ellipsoid, an elliptic paiaboloid, and an elliptic cone. As a numerical example caustic surfaces are calculated for a concave spherical surface and a concave paraboloid.
47 citations
Patent•
19 Oct 1973
TL;DR: An inexpensive, lightweight reflective panel for solar-thermal collector modules of the type including a parabolic reflector for reflecting incident solar radiation onto a fluid carrying conduit positioned along the focal axis of the reflector is described in this paper.
Abstract: An inexpensive, lightweight reflective panel for solar-thermal collector modules of the type including a parabolic reflector for reflecting incident solar radiation onto a fluid carrying conduit positioned along the focal axis of the reflector. A rigid, waterproof, honeycomb panel formed from paper and having a uniform thickness of parabolic shape supports a reflective material. Glass fiber cloth adhered to the outer panel surfaces adds to the panel''s strength and rigidity. An adjustable support system suspends the reflective panel from the fluid carrying conduit and provides a means of adjusting panel curvature to precisely obtain the required parabolic shape. Methods of forming the panels are described which permit the panels to be formed at or near the site of their installation to obviate shipping problems and expense. The methods include the steps of forming an expanded honeycomb core, conforming the core to the required parabolic shape, adhering sheets of skin material to top and bottom surfaces of the core, and adhering a reflective material to the top panel surface.
46 citations
TL;DR: A new single beam spectrophotometer is described in which transmittance is measured by placing samples normal to a parallel beam of light and systematic errors such as detector nonlinearity and stray radiant energy are measured.
Abstract: A new single beam spectrophotometer is described in which transmittance is measured by placing samples normal to a parallel beam of light. Collimation and focusing of the main beam are achieved by means of off-axis parabolic mirrors. The wavelength at which the transmittance is to be measured is selected by a plane grating monochromator having off-axis parabolic mirrors and circular holes as entrance and exit apertures. The instrument has an inherent accuracy estimated to be 0.0001 transmittance unit. Its precision is characterized by a repeatability of 0.00004 transmittance units for neutral-density filters with transmittances between 10% and 30%. The design philosophy used to achieve these results is presented. A discussion of some systematic errors commonly neglected in routine spectrophotometric, measurements is given. Systematic errors such as detector nonlinearity and stray radiant energy are measured.
40 citations
TL;DR: In this paper, a theoretical study of the performance of cylindrical parabolic solar concentrators under ideal conditions is presented. But the authors focus on the application of this type of concentrator in the intermediate temperature range, where wide targets are used.
37 citations
Patent•
17 Jul 1973
TL;DR: In this article, a composite antenna feed subsystem concentrated in a small area at the prime focus of the parabola of a satellite parabolic reflector accomodates a plurality of frequency bands.
Abstract: A composite antenna feed subsystem concentrated in a small area at the prime focus of the parabola of a satellite parabolic reflector accomodates a plurality of frequency bands. The arrays comprising the subsystem are mounted on the top cover of a communication module. A multimode horn is arranged at the center of the subsystem axis which functions at X- and C-band frequencies, and a cross-array consisting of individual elements form the S-band feed, with one arm of the S-band array containing an element mutually shared with the L-band array. Provision is also made for UHF frequencies, and a dipole arrangement for VHF frequencies is arranged around the S-band arms.
13 citations
TL;DR: In this paper, the characteristics of the astigmatic phase error in large parabolic reflector antennas are described and a procedure for focusing an antenna and diagnosing the presence and degree of astigmatism is given.
Abstract: The characteristics of the astigmatic phase error in large parabolic reflector antennas are described. A procedure for focusing an antenna and diagnosing the presence and degree of astigmatism is given.
13 citations
TL;DR: In this paper, the authors extended the analysis to the case where the primary feed illumination is not symmetric, because real primary feeds usually have unequal E - and H -plane beamwidths.
Abstract: Gored umbrella parabolic reflectors with symmetric aperture illumination have been treated analytically in a recent paper. This communication extends the analysis to the case where the primary feed illumination is not symmetric, because real primary feeds usually have unequal E - and H -plane beamwidths. The gore loss and the shift in the defocusing curve obtained using the modified gain expression are in excellent agreement with values measured for a smooth parabolic reflector and a gore parabolic reflector of the same diameter.
11 citations
Patent•
30 Apr 1973
TL;DR: In this paper, the effect of deformation of an antenna parabolic reflector dish on the feedhorn focal point location is measured by reflecting the sun image onto a photographic plate mounted in front of the focal point.
Abstract: A system for measuring the effect of deformation of an antenna parabolic reflector dish on the feedhorn focal point location. A plurality of equally spaced tiny mirrors attached to the parabolic reflector in a concentric circle reflects light onto a photographic plate mounted in front of the feedhorn focal point. The photographic plate contains a predrawn target circle which represents the projected focal point determined from the selected placement position of the tiny mirrors on the parabolic dish. A bore sight apparatus is used to align the parabolic dish with a light source, such as the sun. Spots, representing images of the sun reflected from the tiny mirrors, are recorded on the photographic plate when it is exposed. For a true parabola, the sun images produced by the tiny mirrors on the photographic plate should, theoretically, all fall on the target circle. Thus, any sun images on the photographic plate displaced from the target circle are an indication of distortion of the parabolic dish due to environmental changes.
10 citations
TL;DR: Equations are derived that allow rapid calculation of the effective area of an x-ray telescope before one proceeds to detailed studies utilizing Monte Carlo techniques.
Abstract: The theoretical and practical constraints on designs of grazing-incidence x-ray telescopes are discussed. It is shown that there is a maximum useful diameter for an x-ray telescope. It is further shown that when practical constraints are considered, the maximum reflecting area is not necessarily achieved by utilizing the largest available area within this diameter. Equations are derived that allow rapid calculation of the effective area of an x-ray telescope before one proceeds to detailed studies utilizing Monte Carlo techniques.
9 citations
Patent•
16 Apr 1973
TL;DR: A feed horn for a parabolic reflector includes a feed waveguide capable of supporting a first electromagnetic mode and a cylindrical member surrounding an open-ended radiating portion of said feed guide and located about said open end at a distance to cause a second mode to be supported.
Abstract: A feed horn for a parabolic reflector includes a feed waveguide capable of supporting a first electromagnetic mode and a cylindrical member surrounding an open-ended radiating portion of said feed guide and located about said open end at a distance to cause a second mode to be supported. Said first and second modes as propagating combine to provide a radiation pattern for illuminating said reflector to provide a high performance antenna system.
TL;DR: In this paper, a modification to the halfplane diffraction coefficients is given for a plane wave incident on a curved screen, which is used to calculate the near field of a parabolic reflector under plane-wave illumination.
Abstract: A modification to the halfplane diffraction coefficients is given for a plane wave incident on a curved screen. The result is used to calculate the near field of a parabolic reflector under plane-wave illumination. Comparison with the physical-optics method shows excellent agreement.
TL;DR: In this article, a circularly polarized feed for an S-band high gain antenna system is designed to have a minimum axial ratio when radiating into free space, but when the feed is located at the focal point of a 2-ft diameter parabolic reflector, the axial ratios "blows up".
Abstract: A circularly polarized feed for an S -band high gain antenna system is designed to have a minimum axial ratio when radiating into free space. However, when the feed is located at the focal point of a 2-ft diameter parabolic reflector, the axial ratio "blows up." An experimental technique, which overcomes this difficulty without any change in the basic feed structure, is described. In addition, other RF test results are presented.
01 Oct 1973
10 Jul 1973
TL;DR: In this paper, Farfield directivity patterns for line-array transducers with finite aperture pressure-release reflectors are calculated by using a two-dimensional source-strength integral method.
Abstract: : Farfield directivity patterns for line-array transducers with finite- aperture pressure-release reflectors are calculated by using a two-dimensional source-strength integral method. The directivity patterns obtained when plane and wedge reflectors are shown for both single and multiple sources. Normalized radiation impedances are calculated in order to determine the source-reflector and the source-source interactions. The effects of source size and reflector width are also investigated. The accuracy of the numerical technique is determined by comparing calculated predictions with the measured nearfield and farfield pressure distributions from a line source at the focus of a parabolic reflector. Methods of resolving apparent anomalies in the numerical integral solution are also discussed.
TL;DR: In this paper, a computer program is described for the calculation of the near-axis secondary-radiation pattern of a parabolic reflector for laterally or axially displaced feed, in particular a log-periodic dipole array.
Abstract: A computer program is described for the calculation of the near-axis secondary-radiation pattern of a parabolic reflector. The program has been devised for a laterally or axially displaced feed, in particular a log-periodic dipole array. The illumination-function data are input in the form of radiation-pattern co-ordinates of the feed aerial.
TL;DR: Surface reflections from an off-axis parabolic mirror are analyzed in three dimensions applying the techniques of vector analysis and ray tracing to yield information about the parameters specified in the construction of off- axis parabolic mirrors.
Abstract: Surface reflections from an off-axis parabolic mirror are analyzed in three dimensions applying the techniques of vector analysis and ray tracing. A He–Ne laser is directed onto the mirror surface and held fixed while the parabolic mirror is rotated through an angle of 360° on an axis that is parallel to that of the original paraboloid. The reflection from the mirror traces a closed figure in a plane perpendicular to the paraboloidal axis when the mirror undergoes one complete revolution about its center axis. The shape of this figure depends on the value of the off-axis distance and the focal length; consequently, this figure yields information about the parameters specified in the construction of off-axis parabolic mirrors.
Patent•
11 Jul 1973
TL;DR: In this paper, a weatherproof dielectric reflector for electric waves has been proposed, having a spherical lens, an annular electric wave reflector of predetermined width disposed on the spherical surface of the spherical lens at a position about a horizontal plane passing the central point of the lens or a point vertically spaced apart from the center point of a spherical reflector, a covering for the reflectors and lens, and a support therefor.
Abstract: A weatherproof dielectric reflector for electric waves having a spherical dielectric lens, an annular electric wave reflector of predetermined width disposed on the spherical surface of the spherical dielectric lens at a position about a horizontal plane passing the central point of the spherical dielectric lens or a point vertically spaced apart from the central point of the spherical dielectric lens, a dish-shaped electric wave reflector of predetermined area disposed on the spherical surface of the spherical dielectric lens at a position about a vertical line passing the central point of the spherical dielectric lens and extending downwardly thereof, a covering for the reflectors and lens, and a support therefor.