Showing papers on "Parabolic reflector published in 1997"

Composite rooftop antenna for terrestrial and satellite reception

Abstract: An antenna structure includes a plurality of vertical directed antennas mounted on an insulated cylindrical substrate. A parabolic reflecting antenna is mounted at one end of the cylindrical substrate cavity and a dielectric lens admits radiation through the cylindrical cavity to the parabolic reflector. Optical detectors are located on the cylindrical substrate periphery and exposed to optical signals through an InfraRed (IR) optical filter.

Excitation system for an antenna with a parabolic reflector and a dielectric radiator

Abstract: An excitation system which can be used with sector antennas which do not have circular reflectors is described. The reflector is designed as a rectangular strip which curves parabolically in the direction of its long axis to form a sector antenna. The end face of the radiator has four partial faces which form equal pairs and their opposing faces are arranged with respect to the central axis of the hollow conductor so that the surfaces of the two pairs extend at approximately right angles to each other. The partial faces of the radiator extending in the direction of the long axis of the reflector are large in relation to the two partial faces extending crosswise thereto.

Dual frequency reflector antenna feed element

Abstract: A dual frequency feed element for a parabolic reflector antenna system, comprising a conductive cavity having a central axis, the cavity mounted at the focal point of a parabolic reflector surface and defined about its outer perimeter by an upstanding cavity wall, and having a closed cavity floor and an open top directed toward the reflective surface, a dual frequency radiating element centrally disposed in the cavity and arranged to radiate a first low frequency signal out through the cavity open top to the antenna surface, a conductive floor fixed below the radiating element a distance in relation to the radiant energy for the first low frequency signal, and disposed in the cavity transverse to the central axis thereof to reflect radiant energy for the first signal and, a frequency selective surface fixed below the radiating element, apart from the conductive floor, and transverse to the central axis of the cavity to reflect radiant energy for the second, higher frequency signal while simultaneously being invisible to the lower frequency signal.

Analytical solution for early-time transient radiation from pulse-excited parabolic reflector antennas

Abstract: A closed-form analytical solution is developed for predicting the early-time transient electromagnetic fields which are generated by a perfectly conducting parabolic reflector antenna when it is illuminated by a transient step spherical wave due to an elemental Huygen's source located at the focus. This closed-form time-domain solution, which is valid both near and far from the reflector (and anywhere in the forward region) can be used via the convolution theorem to efficiently obtain the early-time transient fields generated by the same parabolic reflector antenna when it is illuminated by a realistic finite-energy pulse which emanates as a spherical wave from the focus. The transient solution is developed here by analytically inverting, in closed form, the corresponding frequency-domain solution in terms of a radiation integral that employs an asymptotic high-frequency geometrical optics (GO)-based approximation for the fields in the aperture. Numerical results are presented for the transient fields both near and far from the reflector. The fields on boresight exhibit an impulse-like behavior similar to that of the impulse radiating antenna (IRA) introduced by Baum et al. (1989, 1993).

New method for calculating pulse radiation from an antenna with a reflector

Abstract: A simple method for calculating the pulse radiation of an antenna with a reflector is proposed both in the near and far zones. The method is based on substitution of the radiation field from a parabolic mirror by the radiation field from an exciting V-antenna reflected from the mirror. An experimental investigation of the system radiation field and a comparison with the theoretical results have been performed.

Transient Fields of Parabolic Reflector Antennas

Abstract: Requirements to increase the information content of radar and communication systems result in a band width increase and are a reason to investigate and describe the transient fields from ultra wideband (UWB) large antennas1. Furthermore, a need in such an analysis occurs in near field time domain antenna measurements2. In these cases not only the transient far field is of interest. The spatial-temporal near-field distribution is useful too to the optimal antenna arrangement on the complex objects. Mention must be made that many issues of the theory of an impulse radiating antenna. (IRA) are discussed by Carl E. Baum. Everett G. Fart and D. V. Giri3–8. The transient field from the circular focused aperture with uniform held distributions was considered in3. Much attention is given to IRA which consists of a large angle conical TEM feed that attach to a reflector antenna. It was shown that radiated held includes three distinct pacts. The first of these is the direct radiation from the feed structure (prepulse), whirl is of rather low magnitude, but lasts for a fairly long time This is followed by an impulse, which lasts for a brief time and is high in amplitude. Finally, there is a tail expected after the impulse. Closed-form expressions for prepulse were presented in 4. Analysis was extended to include the diffracted fields from the launcher plates and the circular rim of the reflector5. It was shown that there is an exact time-domain match of the spherical and planar TEM waves (inhomogeneous) at the reflector4–7. Thu exact expressions for the acoustic fields on the z axis for a circular aperture were obtained in 8. While the above-mentioned works describe basic properties of transient fields of an IRA, many questions are yet to be investigated.

Glare control sports lighting luminaire

Abstract: A luminaire especially suited for sports and roadway applications. The reflector of the luminaire has a modified parabolic shape wherein a true parabolic curve has been tipped inwardly to produce a tipped parabolic reflector having a circle of focal points centered on the focal point of the original true parabolic curve. The lamp comprises a double-ended arc lamp which is positioned transversely of the central axis of the reflector with the arc of the lamp generally tangent to top dead center of the focal point circle. The luminaire further includes a vertical black partition positioned within the reflector below and forwardly of the lamp and a specular insert in the upper front region of the reflector. The front edge of the specular insert is generally contiguous with the rear edge of a flat upper portion of a visor positioned against the front face of the reflector with the specular insert angled upwardly with respect to the central axis of the reflector and the flat visor portion angled downwardly with respect to the central axis. In an alternate embodiment a stepped lens is provided between the lamp and the front face of the reflector so as to block a direct frontal view of the arc. In a further alternate embodiment a true parabolic reflector bowl in positioned in the back half of the tipped parabolic reflector to provide a narrow concentrated beam. In a further alternate embodiment, the clear lens that covers the front reflector face is replaced by a lateral spread lens to increase the beam width and reduce direct lamp glare.

Device for covering the aperture of an antenna

Abstract: A device is indicated for covering the aperture of an antenna having a parabolic reflector and an exciter. The cover is made of a rigid material. The cover includes a shield ring connected to the reflector and a plastic cover shaped like a flat or obtuse cone having a conical portion which closes the open end of the reflector. The wall of the conical portion of the cover forms an angle between 4° and 6° with a plane that is at a right angle to the axis of the shield ring.

Lighting device for generating a rectangular pattern at the work area, E. G. for illuminating pedestrian crossings

Abstract: A lighting device which can be used for illuminating pedestrian crossings or in other applications where it is necessary to form a defined and uniform rectangular pattern includes a parabolic reflector element and a planar screen with an array of cylindrical microlenses or microprisms on a surface thereof.

Optical radar apparatus

Abstract: An optical radar apparatus, having a structure such that light generated by a laser generating means 1 is emitted to an object 100 while scanning the same, light reflected by the object 100 is reflected by a reflected-light reflecting means 10, and then a parabolic mirror or a concave mirror 19 receives reflected light above, is arranged to have a light receiving device 20 disposed at the position of the focal point of the parabolic mirror or the concave mirror 19 so as to obtain the distance to the object 100 and the direction of the same in accordance with propagation delay time taking from light emission by the light generating means 1 to receipt of reflected light by the light receiving device 20.

Broadband acoustical transmitting system

Abstract: An acoustical transmitting system and method for producing a narrow beam of acoustic energy over a broadband operating frequency range utilizes a parabolic reflector dish, a horn-loaded compression driver for directing acoustic energy toward the dish's reflecting surface, and a low frequency driver mounted behind a central aperture in the dish for producing acoustic energy that combines and interacts with the reflected acoustic energy produced by the horn-loaded compression driver. An input signal processing circuit is provided to condition the audio signal to the horn-loaded compression driver and the low frequency driver to achieve on-axis gain and off-axis cancellations at low frequencies. The addition of the low frequency driver to the reflector dish system effectively extends the ability of the system to produce and transmit acoustic energy in a narrow distribution pattern at frequencies below 1000 Hz using a four foot diameter dish.

Calibration and upgrades of the XMM vertical EUV/X test facility: FOCAL X

Abstract: The x-ray multi-mirror mission is the second of the four cornerstone projects of the ESA long term Program for Space Science. The payload comprises three co-aligned high throughput imaging telescopes called mirror modules. The 'Centre Spatial de Liege' (CSL) is in charge of optical and environmental qualification test of each of these MMs. To perform optical tests, a vertical test facility (FOCAL X) has been developed by CSL. An EUV channel providing an 800 mm diameter collimated beam is used. A trade-off leading to the selection of an electron cyclotron resonance EUV source is presented. Impact of the coating on the microroughness of the EUV optics is assessed and its homogeneity across the optical surfaces is measured. Another feature of the facility is an x- ray channel providing a 50 (DOT) 8 mm2 collimated beam. It has been characterized for x-ray effective area measurement. It is the first time that an off-axis parabolic mirror is used for this purpose.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Corrector design with active vase mirrors that allows a fixed telescope to access a large region of the sky

Abstract: We investigate a family of two-mirror correctors to compensate for the aberrations of a parabolic mirror observing at a large angle from the zenith. We constrain our designs to optical elements that can be built with currently available technology. The secondary and the tertiary mirrors are warped by Zernike polynomials, which we know can be generated with active vase mirrors. The performances of these corrector designs are usable for imagery.

Random wavelength access monochromator incorporating coaxial off-axis parabolic OAP reflectors

Abstract: A random wavelength access monochromator incorporates a pair of coaxial off-axis parabolic reflectors configured so that the spherical aberrations introduced by the reflectors cancel each other. Light enters through an entrance slit and impinges upon a first off-axis parabolic reflector that collimates the beam and directs it towards a stationary grating. The grating in turn defracts the light and directs it towards a high speed scanning mirror which reflects the defracted light onto a second off-axis parabolic reflector which in turn focuses the beam to an exit slit. Both off-axis parabolic surfaces share the same axis of revolution and the same collimated beam axis. In order to make the apparatus practical, the beam is folded twice so that the exit point is focused away from the internal path of the beam. The resulting instrument is capable of accepting a broad wavelength beam of light, dividing that broad band light into discrete wavelength bands of less than 1 nm optic wavelength, and emitting only the desired wavelength band.

A corrector design using active vase mirrors that allows a fixed telescope to access a large region of the sky

Abstract: We investigate whether a three-mirror system, having secondary and the tertiary mirrors with surfaces warped by Zernike polynomials generated by active vase mirrors, is suitable to do the corrections of a fixed parabolic mirror observing at large angles from the zenith. We obtain designs of correctors with remarkable images and control of the distortion of the field of the view contained within a field greater than 15 Deg.

Mechanical beam-modulation method for infrared gas analyser

Abstract: The method uses a radiation source (4), which rotates around an axis (5) that is perpendicular to the beam path (9). The source has at least one fan-shaped emitting side and is mounted on a shaft (2), that connects with motor (1) and is held in a bearing (6) at the other end. One or more shutters or slits (36) are arranged in a plane perpendicular to the beam path. The slits are disc-shaped and combined on a drive belt (35) so that they rotate in a common direction or in counter-rotating directions. The beam path from the radiation source is directed at a parabolic mirror from which the reflected beam is perpendicular to the rotation axis of the source.

Portable solar energy appliance with cooking and water heating

Abstract: The appliance has a frame formed like a conventional umbrella or parasol frame, with a special covering made of thin, highly-polished aluminium foil. The outside of the foil has a thin plastics foil coating, and the frame forms an octagonal parabolic reflector (1) when open. The reflector concentrates incoming solar radiation in a focal point, which is located on the line of the inclined umbrella stick axis (4), and above it. The reflector is fastened to a stationary fold-down stand (6), via a pivot or turning joint (5). A cooker or water-heater plate (7) is screwed to the top of the stand. A second fastener unit consists of a pivoted forked connection and a telescopic rod (8), for continuous and precise inclination of the reflector into the sun.

Lighting system and lamp with optimal filament placement

Abstract: A lighting system for projecting a beam of light has a light source and a concave reflector having a central axis. The center of the light source is located at a position other than at the focal point of the reflector, i.e. between the reflector surface and the focal point of the reflector for an ellipsoidal reflector and forward of the focal point for a parabolic reflector. This placement provides a greater light output than is achievable by positioning the light source at the focal point of the reflector. The preferred light source is an improved lamp having an incandescent filament having a central linear helical portion aligned with a central axis of the reflector and a peripheral helix portion around the central portion so as to concentrate the emission of light along and about the central axis of the filament.

Hybrid parabolic sound collector

Abstract: PROBLEM TO BE SOLVED: To provide a sound collector for efficiently collecting sounds at distant places. SOLUTION: This hybrid parabolic sound collector for collecting sounds from distant places is provided with a parabolic reflector 1 turning its parabolic concave toward a sound source, microphone 3 of sub-cardioid characteristics installed at the focal point of parabolic reflector while being turned opposite, and superdirective microphone 2 installed on the center line of parabolic reflector closer to the side of sound source adjacently with the microphone 3 of sub-cardioid characteristics while being turned toward the sound source. Then, the outputs of both the microphones are synthesized so as to clearly collect the sounds from distant places. COPYRIGHT: (C)1998,JPO

Parabolic reflector aerial system with dual receivers for two satellites

Abstract: The satellite signal receiving aerial comprises a reflector (C) and two associated converters (C1, C2), with an integrated waveguide. A fixed support (B) is provided for the first converter (C1), and mounted on this is an asymmetric and reversible stirrup providing a support for the second reflector. According to the position of the stirrup, it is possible to obtain two different possible elevations for the line of sight of the aerial, the azimuth remaining the same for both. It is also possible to switch the converter position between these two settings as required. A coaxial wire provides a connection from the converters, to transfer the received signal to the processing circuitry.

Parabolic reflector and portable television antenna

Abstract: PROBLEM TO BE SOLVED: To obtain the compact antenna receiving a BS broadcast and a broadcast at an UHF band. SOLUTION: Slits 3-1 to 3-6 are formed to a conductor face formed to be a parabolic face to separates the conductor face. Captions 1-1, 1-2 are used for a radiator at a UHF band and a BS reflecting mirror and remaining captions 2-2-2-4 are used for BS reflecting mirrors. Thus, a parabolic reflector 10 is used by the antenna the UHF band and the BS reflecting mirrors.

Disc focusing solar heat collector

Abstract: The solar heat collector consists of casing, light incident port, spiral endothermic pipe and heat medium inlet and outlet. It is mounted over the disc parabolic mirror, and its light incident port is at the focus of parabolic mirror. The light ray incoming the endothermic cavity is multiple-reflected and the heat energy is absorbed by the endothermic pipe, which transfers heat energy to circularheat medium for efficient absorption.

Parabolic reflector antenna energising system

Abstract: The antenna energising system has a dielectric radiator (3) at the end of a hollow waveguide (2), for the electromagnetic waves, positioned centrally relative to the parabolic reflector (1). This is provided with a metallised end face acting as a sub-reflector. The parabolic reflector is formed from several rectangular metal strips, the end face of the radiator being provided by two opposing pairs of partial surfaces (8,9,10,11), on either side of the central axis. The partial surfaces, in the direction of the main axis (A) of the reflector, are larger than the partial surfaces in the perpendicular direction.

Light source employing reflective led

Abstract: PROBLEM TO BE SOLVED: To obtain a high luminance reflective LED applicable to an apparatus requiring a large quantity of light and having a significant effect on the fluctuation in the quantity of light by eliminating fluctuation in the quantity of light to be emitted. SOLUTION: A dummy block 34 is provided between a chip 10BL and a lead frame 26 and the chip 10BL is disposed while being shifted slightly from the focal point of a parabolic mirror. This structure suppresses fluctuation in the quantity of light in a region where the parallelism is substantially sustained for the light reflected from the parabolic mirror and it can be employed as a light source for color conditioning requiring a color image.

Parabolic mirror adapted-alignment for high speed-high power laser welding with an oblong focused beam spot

Abstract: For industrial laser welding of metals at high speed, a simple, cost effective method to produce an oblong focused beam spot is detailed. The method takes advantage of the effect of beam misalignment on the focus characteristics of an off-axis parabolic mirror. For a high power laser beam of circular cross section and substantially axis-symmetric divergence, the laser beam is oriented with a controlled incidence angle on a parabolic focusing mirror. At the proper depth of focus, the resultant focused beam spot on the workpiece is oblong. The longitudinal direction of the oblong focused spot is aligned parallel to the direction of welding. Keyhole mode welding is achieved.A design of experiments investigation, within the parameters of an L9 3-level orthogonal matrix, is conducted in order to compare laser welding with a small circular spot and with an oblong spot. A 3 kW CO2 laser and a 150mm parabolic focusing mirror are used for bead-on-plate welding. Shapes of the experimentally obtained oblong focused beam spot are compared with numerical analysis software predictions. Controlled process parameters were laser power, weld speed and laser focus spot size and aspect ratio. Measured weld parameters include weld top bead and root width and weld cross section area.

Erect optical system

Abstract: PROBLEM TO BE SOLVED: To obtain small, lightweight, and inexpensive observation optical equipment by constituting the equipment so that main light beams are made incident on a 2nd parabolic surface and reflected to become a parallel light beam and reach an ocular. SOLUTION: All luminous flux after the main light beams 10, 10'L, and 10'R are made parallel by passing through a parallelizing lens 3 is adjusted and made incident on a 1st parabolic mirror 4. The 1st parabolic mirror 4 has its parabolic surface axis 20 parallel to the 1st optical axis 10 of this observation optical system, the focus O of its parabolic surface is positioned outside the luminous flux which is made incident on the parabolic mirror 4, and the parabolic surface is so sized to spread around the optical axis 10 of the observation optical system so that the luminous flux from an object image 2 is effectively reflected. Then main light beams 11, 11L, and 11R which are reflected and converted into convergent light beams are made incident on an image-side control lens 5 provided at the focus O of the 1st parabolic mirror 4 to pass through it, and then cross one another to become divergent light beams, which are made incident on the 2nd parabolic surface 6 and diverged to become main light beams 12, 12L, and 12R which are parallel to the axis 20 of the parabolic mirror and also parallel to one another, so that they are made incident on the ocular 7.

Optical transmission and reception module

Abstract: PROBLEM TO BE SOLVED: To provide an optical transmission and reception module of which reception-only optical module is attachable and detachable and which is easily manufactured at a low cost. SOLUTION: A package 12 is provided with connection holes for optical fibers 9 and 10 and in the package 12, a lens 8, a transmission type hologram optical element 6, a photodiode 2, a rotary parabolic mirror 3, and a semiconductor laser 1 are provided. The light which is sent in by the hologram optical element 6 from the 1st optical fiber connection hole is split into light beams with 1st wavelength and 2nd wavelength, and the light with the 1st wavelength is made incident on the photodiode 2 and the light with the 2nd wavelength is made incident on the rotary parabolic mirror 3. The rotary parabolic mirror 3 reflects the incident light with the 2nd wavelength regardless of the incident angle so that the reflected light is made incident on the 2nd optical fiber connection hole through the hologram optical element 6 and lens 8.

Cassegrainian Gregorian-type null correctors for surface measurements of radio telescope reflectors

Abstract: The (sub)millimeter wavelength radio observatory of the next generation will probably be an interferometer array of some 50 telescopes with parabolic reflectors 10–15 m in diameter. At this scale of mass production it is convenient to have at hand for workshop assembly a reflector surface measurement technique that is precise and easy to operate. We discuss the possibility of reflector measurements based on 10.6-µm CO2 laser interferometry using Cassegrainian/Gregorian-type null correctors.

Cost, brightness, and lifespan trade-offs of light sources for small format display systems

Abstract: In this paper, works on optimization oflight sources for small format projection systems are reported such as DMD, TRLCD, and ITT systems. Results using short arc Xenon lamps versus modest gap width HID and relatively long gap width RID lamps are compared with several designs of the Compound Orthogonal Parabolic Reflector (COPR«), reflector systems, and with relatively deep elliptical reflectors. It can be shown that the diameter ofthe COPR« reflector is independent of the resulting focal spot size, but the gap width is a function ofthe spot size. For intensity or total light for a given iamp, the COPR« is 60% better than the elliptical reflector. If aperture size is not important, than the comparison is moot. A new concept of imaging ray tracing versus classical point and ray emission method are compared specifically for the evaluation of relative intensity of "light" through a given aperture dimension. It can be demonstrated that the imaging method is much more efficient to provide first order results for optical designers. A hyperboloid ray concentrator is introduced as a method to relax the small aperture requirement for small format imaging systems. Cost trade-off will be provided on typical, currently available lamps.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.