Showing papers on "Parabolic reflector published in 1968"

Fields in the image space of symmetrical focusing reflectors.

Abstract: The fields scattered by circular symmetric reflector illuminated by a linearly polarised wave incident normally on the aperture are calculated from the induced surface currents. It is shown that the fields in the axial region can be represented by a spectrum of near-spherical hybrid waves propagating along the axis. For large microwave focusing reflectors, the wavefronts are effectively plane in the significant part of the image space. The axial wave fields are linear combinations of the TEln and TMln fields appropriate for circular metal pipes, but can be bounded only by anisotropic-reactance surfaces. Axial-wave theory is used to investigate the characteristics of the fields in the focal region of a paraboloidal reflector, when the incident wave is uniform and plane. For radiotelescope focal ratios, the image structure differs significantly from the classical Airy pattern, deduced by scalar analysis, of optical focusing systems. Energy vortexes circulating about the dark rings influence the efficiency obtainable from aperture-type feeds in the focal plane. Application of axial-wave analysis to spherical reflectors, and the synthesis of high-efficiency low-noise feeds, using hybrid-waves in corrugated guides, are described briefly.

Vehicle headlamp with two light sources

Abstract: A main parabolic reflector has an iodine lamp located slightly in front of the reflector focal point. A masking element below the lamp defines a plane below which no light from the lamp strikes the reflector. An auxiliary reflector having an aperture substantially one half that of the main reflector has a second iodine lamp at its focal point. The vertical axis of the auxiliary reflector is spaced from the vertical axis of the main reflector, and the aperture of the auxiliary reflector is tangent to the plane defined by the mask.

Parabolic reflector antennas

Abstract: This application discloses a method for making a paraboloidal surface. In particular, such a surface is made by immobilizing the circumference of a circular portion of a thin diaphragm and applying a sufficient uniform pressure to the circular portion to permanently deform it. It has been discovered empirically that the surface thus produced is paraboloidal to a sufficiently high degree of approximation to be useful as a microwave reflector antenna. In addition, refinements in the final shape can be realized by using a plurality of closely spaced blanks in the deformation process.

Some results of electronic compensation for surface profile errors in parabolic reflectors

Abstract: This letter describes the basic principles of a proposed system for compensating for the effect of surface profile errors in parabolic reflectors. It also describes some experimental results which verify the technical feasibility of the proposals and discusses some implications of its future development.

Broad band antennas having spiral windings

Abstract: A broad band antenna or feed for a parabolic reflector having a pair of spiral windings skewed with respect to the axis of a conical support surface on which they are wound in alternating relationship. Two such supports are rotatably mounted with their axes offset at an angle from the reflector axis so as to conically scan the target area. The feed achieves maximum illumination of the control portion of the reflector and provides a constant squint angle with respect to the reflector axis over a broad band of frequencies.

Solar simulator for a 3-m space environment chamber.

Abstract: The geometric-optical principles of a solar simulator for 1.5-m diam test objects are described and discussed. The characteristic features of the optical arrangement are a special configuration of nine individual radiation sources, and a mosaic mirror, consisting of more than 1000 single mirrors. The mosaic mirror permits the reference plane (rated diameter 1.5 m) to be evenly illuminated by well collimated light. For lesser demands with regard to uniformity and collimation the mosaic mirror can be readjusted so as to serve larger or smaller test objects (the latter refers, for instance, to solar research satellites exposed to intense irradiation). The method of adjusting the mosaic mirror is described. A possible modification of the system for larger solar simulators is also discussed.

Portable parabolic reflector for microwave energy

Abstract: A PORTABLE PARABOLIC MICROWAVE REFLECTOR GENERALLY IN THE FORM OF A CROSS COMPRISES A SERIES OF MALE AND FEMALE ALUMINUM CASTINGS JOINED TOGETHER BY MEANS INCLUDING AN ALIGNMENT PIN AND SPRING-LOADED BALLS. ASSEMBLED REFLECTOR SECTIONS ARE SUPPORTED BY WELDED, TUBULAR A-FRAMES THAT BECOME ATTACHED TO THE REFLECTOR BY MEANS OF A SERIES OF MALE AND FEMALE ALUMINUM CASTINGS IN CONJUNCTION WITH AN ALIGNMENT PIN, LOCKED IN PLACE BY SPRING-LOADED BALLS. THE A-FRAMES ATTACHED TO WHATEVER SUPPORT STRUCTURE IS REQUIRED TO SUPPORT THE ANTENNA.

Improvements in and relating to light fittings

Abstract: 1,102,270. Electric lighting fittings. FALKS Ltd. 19 Jan., 1967 [18 Aug., 1966], No. 37093/66. Heading F4R. A fitting, especially for fluorescent discharge lamps, includes an elongated parabolic reflector 12 having transverse wedge-shaped louvres 56 point downwards. The reflector is supported by a casing 10 in which is the control gear 35 for the lamp, by means of permanent magnets 32 on the casing which co-operate with keepers 42 on the reflector. The casing has a channel element 18 surrounding the opening into which a flange on the reflector fits. The top of the reflector is cut away to allow for the passage of the discharge tube, a reflector corresponding to the cutaway portion of the reflector 12 being mounted above the tube. The fitting is supported in the ceiling by arms 67 mounted on adjusting screws inside the casing.

High temperature reflectance measurements with the paraboloid reflectometer.

Abstract: High temperature directional reflectance measurements of ablative materials as function of sample temperature using paraboloid reflectometer

Improvements in or relating to microwave aerial assemblies

Abstract: 1,099,429. Aerials. MINISTER OF TECHNOLOGY. Dec. 5, 1966 [Dec. 3, 1965], No. 51400/65. Heading H4A. A microwave aerial assembly comprises a parabolic reflector 1 having a horn or other primary feed 5 at its focus, and a secondary plane reflector 3 rigidly secured to the reflector 1 by a structure 2. The plane in which the surface of the reflector 3 lies passes near the focus of the reflector 1, and is inclined to its axis by an angle # in the range 30 to 60 degrees. The horn 5 may protrude through the reflector 3, or may be behind it, when an aperture is provided for the beam directed at the reflector 1. The structure 2 is pivotally mounted on a trunnion 6, which is mounted on a turntable 7, so providing for rotations in elevation and in azimuth. If the angle # is less than 45 degrees the focal length (F) of the parabolic reflector 1 is made substantially equal to 1/ 4 cot #/ 2 times its diameter (D). If the angle # exceeds 45 degrees, F is made substantially equal to “ (tan 0 + see 0) times D. If the angle # is substantially 45 degrees, F is made approximately 0A6 D.

Directional 420-Hz Sound Source

Abstract: A 24-foot compliant-tube parabolic reflector, with a flextensional transducer at its focus, has yielded acoustic source levels up to 122 dB?baryd1 at 420 Hz in 85 feet of water off Fowey Rocks near Miami, Fla. The projector is part of a research program to study underwater sound propagation and related environmental parameters. Modulation signals of continuous wave pulses and pseudorandom sequences are transmitted by wire from the Institute of Marine Sciences Laboratory, Miami, to the transducer, a distance of 12 miles. Bottommounted hydrophones are employed at various distances, with the principal sensors on the island of Bimini, which lies 45 miles eastward across the Florida Straits. The reflector provides a main lobe of 28° at the half-power points; the back lobes are down more than 25 dB and the directivity index is 15 dB. The effective mechanical Q of the transducer-reflector combination is 4. At the present depth, the transducer is cavitation limited to an acoustic output of 4 kW.

Rays from a Parabolic Reflector for an Off Focal-Point Source

Abstract: The exact solution for rays emanating from a two-dimensional parabolic reflector is obtained using Fermat's principle. The results are presented graphically (using the IBM 1627 plotter) for various positions of the source, both close to and far from the focal point of the mirror.

Pressure-formed parabolic reflectors for millimeter wavelengths

Abstract: An empirical investigation of metallic diaphragms deformed by uniform normal pressure to produce accurate parabolic reflectors is discussed. 30-cm diameter ( f/D =0.4 ) reflectors produced by this technique were measured mechanically and found to have maximum deviations of only 0.5 mm or \lambda/20 at 30 GHz from a true paraboloid within a circle of 14-cm radius. Electrical measurements at 30 GHz are discussed.

Analysis of the maximum performance of a paraboloidal solar collection system for space power

Abstract: Parametric analysis of effects of concentrator surface errors and rim angle, collection system orientation error, and receiver temperature on paraboloid solar collector thermal efficiency