Showing papers on "Reflector (antenna) published in 1991"

Spatial positioning system

Abstract: A spatial positioning system includes fixed referent stations (101, 102 or 103) which emit rotating, divergent laser beams (130) and a portable reflector (200). Each fixed station also includes a detector (330) and a processor (120). The portable reflector may include retroreflectors or transponders (340). When the rotation of the laser beam is such that it is in line with a portable reflector, the transmitted laser beam is reflected off the portable reflector and received at the fixed receiver. For any point which is crossed by the fanned laser beams of a fixed station, a horizontal angle can be determined. Once these horizontal angles are known for three fixed stations, the point of intersection of three planes, and thus the three-dimensional position of the point, is determined.

Squeezing in fibers with optical pulses.

Abstract: A novel method of squeezing with optical pulses in a fiber ring reflector is demonstrated experimentally. Squeezing of greater than 5 ± 0.3 dB has been observed. The pump is separated from the squeezed radiation with a fiber ring reflector and can be reused, in principle fully, as the local oscillator. The detection is at low frequencies (35–85 kHz) and is unaffected by guided-acoustic-wave Brillouin scattering.

Millimeter wave and infrared sensor in a common receiving aperture

Abstract: The present invention is an integrated millimeter wave (MMW) and an infrared (IR) common aperture sensor employing a common primary reflector for infrared and millimeter wave energy. An active transmitter/receiver millimeter wave horn assembly located at the focus of the primary mirror transmits and receives millimeter wave signals off the primary reflector. A selectively coated dichroic element is located in the path of the millimeter wave energy on the axis between the feed and the primary reflector. The dichroic element reflects infrared energy from the primary reflector to a focal point and at the same time transmits and focuses millimeter wave energy. An optical system relays the infrared energy to a focal plane behind the primary mirror. The dichroic element transmits and focuses millimeter wave energy without significant attenuation such that optical and millimeter wave energy may be employed on a common boresight. Improvements in the feed assembly include a four channel waveguide structure capable of azimuth and elevation determination in sum and difference configurations. A baffle and cold stop shields the optical system from unwanted infrared radiation. Electrical transmit and receive circuitry and a correction circuit provide high probability of detection and low false alarm rate.

Plasma reflectors for electronic beam steering in radar systems

Abstract: The author describes investigations into methods of generating a planar plasma for use as a reflector for radar waves. The use of the plasma reflector could allow electronic beam steering at frequencies above what is generally viable for phased arrays. Three aspects of the planar plasma production are investigated: localization of the plasma, main plasma production, and long-term viability of the system. Possible applications include ship-based antennas at X-band, airborne antennas at 94 GHz, and space-based antennas at 60 GHz. The author discusses system considerations for the three potential radar configurations. Results and potential small-scale experiments to test various aspects of the concept are discussed. >

Method and apparatus for automatic acquisition and alignment of an optical beam communication link

Abstract: A method and a preferred apparatus for the searching, acquisition and locking into boresight alignment of two remote optical beam transceivers suitable for use in satellite communications. A first transceiver operates in a search mode while acquiring a communications link with a second transceiver operating in a stare mode. Each transceiver has an optical axis and a retro-reflector that reflects incident beams that are not substantially aligned with the local optical axis while not reflecting all incident beams substantially aligned with the local optical axis. Each transceiver includes an axis-aligned beam transmitting source, a axis-aligned optical detector for incoming beams, a pointing system for aiming the local optical axis in any direction over a hemispherical range, and a beam tracker for maintaining boresight alignment following acquisition. The decision processor includes means for distinguishing between optical beams reflected from the second transceiver and optical beams transmitted by the second transceiver. In operation, the reflected beam increases in intensity as the two transceivers approach alignment but drops to zero as the transceivers attain boreslight alignment. The preferred apparatus includes a matched pair of reflecting telescopes rigidly mounted on a gimballed platform with the transmitting and receiving telescope axes precisely aligned and parallel. Each telescope includes a primary reflector, a secondary reflector with a Cassegrainian focus behind the primary reflector and a tertiary retro-reflector behind an aperture at the vertex of the primary reflector.

FLAPS: conformal phased reflecting surfaces

Abstract: A technology applicable to the reflector antenna field is introduced. FLAPS (flat parabolic surface) allows the use of low-cost fabrication techniques to perform various collimating reflector functions, independently of any specific geometric shape, such as would be required with conventional reflectors. The various elements of control afforded by FLAPS technology allow versatile operation in a variety of simultaneous applications not normally compatible with conventional reflector designs. >

Apparatus and method for substrate heating utilizing various infrared means to achieve uniform intensity

Abstract: A reflector array employs a number of linear, tubular heater lamps arranged in a circle concentric with the substrate to be heated. Some of the lamps have focusing reflectors and the remainder have dispersive reflectors. A peripheral cylindrical reflector surrounds the lamps and their associated reflectors. The combined reflectors permit balancing the thermal radiation intensity across the surface of the substrate.

Semiconductor multilayer reflector and light emitting device with the same

Abstract: A semiconductor multilayer reflector (Distributed Bragg Reflector) includes a plurality of first quarter-wavelength layers each having a high refractive index, a plurality of second quarter-wavelength layers each having a low refractive index, and high concentration impurity doping regions. The first and second layers are piled up alternately, and each of the doping regions is formed at a heterointerface between the first and second layer. In this structure, the width and the height of the potential barrier at the heterointerface becomes small, so that tunnel current flowing through the multilayer reflector is increased.

Analysis of a two-stage linear Fresnel reflector solar concentrator

Abstract: The two-stage linear Fresnel reflector solar concentrator is analyzed via an in-depth study of an installed, nominally 220 KW{sub t} system. The concentrator includes: a primary linear Fresnel reflector comprised of curved mirrors and a secondary nonimaging CPC-type trough with a tubular receiver. The principal practical design options for the secondary concentrator are evaluated. In this paper, via a computer simulation which includes ray-tracing of the primary reflector, the authors evaluate the sensitivity of energy output to: concentrator optical errors, system geometry, tracking mode, and the option of using flat versus curved primary mirrors. The two-stage Fresnel concentrator can be considerably less expensive than the corresponding parabolic trough collector, but is found to deliver about one-fourth less yearly energy. However much of this difference could be eliminated through the use of higher-quality CPC reflectors.

Remote seismic sensing

Abstract: Methods and apparatus are provided for remotely sensing motions of the earth from the Doppler shift of reflected electromagnetic waves. The apparatus is based on a heterodyne continuous wave or pulsed laser system. The airborne laser system described herein is intended to remotely sense seismic motion. Motion of the earth's surface, when coupled to a reflector, causes a continuously shifting frequency (Doppler) of the reflected sensing laser beam, the Doppler frequency being proportional to the particle velocity of the ground. The method uses electromagnetic waves reflected from reflectors, some of which are coupled to the earth's surface. Similarly, "inertial" reflective surfaces (i.e., vibrationally isolated from any earth motions) are also located at the surface of the earth and employed by the apparatus and methods of the present invention. Both an inertial reflector and an earth-coupled reflector are positioned at each location for which seismic signals are desired.

Beam diffraction by planar and parabolic reflectors

Abstract: In the complex source point technique, an omnidirectional source diffraction solution becomes that for a directive beam when the coordinates of the source position are given appropriate complex values. This is applied to include feed directivity in reflector edge diffraction. Solutions and numerical examples for planar strip and parabolic cylinder reflectors are given, including an offset parabolic reflector. The main beams of parabolic reflectors are calculated by aperture integration and the edge diffracted fields by uniform diffraction theory. In both cases, a complex source point feed in the near or far field of the reflector may be used in the pattern calculation, with improvements in accuracy in the lateral and spillover pattern lobes. >

Compact antenna test ranges

Abstract: Antenna test ranges are required to be capable of measuring the radiation and scattering characteristics of high performance antennas and to operate over a wide range of frequencies. The compact antenna test range (compact range) can fulfil these requirements very well and has established itself as a versatile indoor test range capable of measuring medium to large size antennas over the frequency range of 1 to 300 GHz. The compact range uses one (or more) collimating reflectors to create a region of plane waves, called the quiet zone, in front of a reflector. The paper reviews the principles, history and design of compact ranges. The various types are described and their relative advantages compared. The compact range can be used for both antenna measurements and radar cross-section measurements and shows considerable promise for further development in the future.< >

Front surface emitting diode laser

Abstract: A front-surface emitting, vertical-cavity laser and its method of making in which a vertical laser cavity with Bragg reflectors and an active layer, preferably formed by a quantum well, is formed on a substrate. Lateral current confinement is achieved by implanting a conductivity-reducing ion into the region surrounding the quantum well. Electrical contact to the upper side of the active layer is achieved by implanting a conductivity-increasing ion into the region surrounding the cavity between the active layer and the upper reflector. By such an electrical contact, the upper reflector can advantageously be composed of dielectric layers. Light is then emitted through the upper reflector.

Fresnel zones in the light of broadband data

Abstract: The investigation of zero-offset response to circular reflectors of increasing Fresnel zone size shows that reflection response is a constant and is independent of reflector size, except when the reflector diameter is so small that the diffractions interfere with the primary reflection. The extent of this effect is dependent upon vertical resolution and the time separation of the primary reflector and the diffraction. Interference occurs for reflectors smaller in diameter than the first Fresnel zone. Migration removes this interference.For broadband data the Fresnel zone solution breaks into two parts: the primary reflector and the edge-effects diffractor. With broadband seismic data, reflections and diffractions separate in time, except at locations near faults or very small bodies. Reflections are the seismic response to interlayer discontinuity and are independent of reflector size. Diffractions are the seismic response to lateral discontinuities and edges and depend on proximity to--and geometry of--the edge. Except in the locale of an edge, broadband reflections and diffractions are separated physically on the section and mentally by the interpreter. Furthermore, standard CMP processing attenuates diffractions, especially when CMP lateral offset is some distance from the diffractor.

Multi-level probe and system for measurement of physical conditions in liquid-containing tanks

Abstract: A multi-level probe for sonic range measurements utilizes a plurality of parallel reflectors that each include an opening arranged coaxially about a beam of ultrasonic energy transmitted along a reference axis from an associated transducer. The opening in each reflector permits most of the sonic energy to pass to a subsequent reflective surface, while the periphery about the opening provides echo signals for determining physical conditions in the environment through which the sonic energy has passed. A novel system is used for determining physical conditions that are a function of time differences between signals from different reflectors, calculated with a highly efficient digital signal processing algorithm.

Motor vehicle headlamp

Abstract: A motor vehicle headlamp having an improved mounting structure of an extension reflector provided between the front lens and the reflector of the headlamp. An extension reflector, formed separate from the lamp body, is provided between the reflector and the front lens. The front end of the extension reflector is held adajcent to or in contact with the inner surface of the front lens to minimize the gap between the extension reflector and the front lens, and the rear end of the extension reflector is spaced from the reflector so that the extension reflector cannot interfere with the opening end portion of the reflector during the aiming operation of the reflector. The headlamp may be combined with other lamps in such a manner that the other lamps are arranged on both sides of the headlamp inside a single lamp body with the headlamp and other lamps juxtaposed with one another, and light shielding walls are provided for the lamps on both sides of the headlamp to cover the gaps between the reflector and the extension reflector.

Reflected optical power fiber test system

Abstract: A system for testing an optical fiber used in communications including a light source connectable to provide light to one end of a fiber under test, an optical power detector connectable to receive light from the same end of the fiber under test, a reflector at the other end of the fiber under test, and monitoring means operatively connected to the light source and detector to make a baseline measurement of optical power reflected by the reflector and subsequent measurements of optical power reflected by the reflector and compare the subsequent measurements with the baseline measurement to determine if there has been a change in optical power reflected by the reflector, the baseline measurement and the subsequent measurements involving no more than a single pulse of light from the light source.

Connector for coupling of laser energy

Abstract: A coupling system for coupling a beam of radiant energy from a laser to a fiber optic cable includes a secondary transmission path which surrounds the input end of the fiber optic cable and provides an optical path for energy which is not transmitted by the fiber optic core but is lost. Displaced from an output end of the secondary transmission path is a multi-faceted reflector. The reflector is displaced sufficiently from the output end of the secondary transmission path so that the power density of the radiation incident thereon is reduced sufficiently so as to not damage the facets thereof. The coupling system is contained within a heat sink which receives the reflected and lost radiant energy harmlessly converting same to heat.

Dual reflector scanning antenna system

Abstract: A fixed feed dual reflector scanning antenna system 10 having a low moment of inertia is disclosed herein. The inventive dual reflector antenna system 10 includes an antenna feed structure 16 for emitting electromagnetic radiation. The antenna system 10 further includes a subreflector 12 for redirecting the emitted radiation. The subreflector 12 is intersected by a subreflector longitudinal axis Ls at a rotation point proximate a vertex 20 of the subreflector 12. A main antenna reflector 14 circumscribing a main longitudinal axis Lm projects radiation redirected by the subreflector 12 as an antenna beam. A mechanical arrangement 22 rotates the subreflector 12 about the rotation point so as to vary the angular orientation between the subreflector longitudinal axis Ls and the main longitudinal axis Lm. In this manner the antenna beam is scanned relative to the main longitudinal axis Lm.

Levitating support and positioning system

Abstract: A levitating support and positioning system (10) is provided for orienting an electromagnetic energy reflecting assembly (40). System (10) includes a reflective member (60) supported by an annular ring (50) having a plurality of superconductors (70) disposed thereon. Ring (50) is levitated above a base surface (20) by means of a plurality of electromagnetic assemblies (30), each of the electromagnetic assemblies (30) corresponding to a respective one of the plurality of superconductive elements (70), whereby the magnetic fields generated by the electromagnetic assemblies (30) are repelled by the respective superconductive elements. The orientation of the support ring (50), and the reflector therewith, is adjusted by changing the relative magnetic field strength between each of the electromagnetic assemblies (30), allowing the reflector to be directed in both elevation and azimuth.

Moment-method analysis of large, axially symmetric reflector antennas using entire-domain functions

Abstract: The moment-method technique utilizing entire domain basis functions is applied to the analysis of large, axially symmetric reflector antennas. The electric surface current is modeled as a finite series of sinusoids whose domain consists of the entire generating curve. This expansion results in a matrix size of less than 5% of that produced with subdomain basis functions. Only a slight increase in the CPU requirements occurs from this analysis. The results from this technique show good agreement when compared to both physical optics and a subdomain-based moment-method formulation on small, axially fed paraboloidal and hyperboloidal reflector antennas. Extension to a large 100- lambda paraboloidal reflector with f/D=0.4 produces results comparable to that obtained using physical optics. Convergence is obtained with as few as two expansion terms per wavelength. Discretization of the generating curve with four points per wavelength leads to results which agree within 0.5 dB over data from a more densely defined curve. >

Array fed reflector antenna for transmitting & receiving multiple beams

Abstract: An array fed reflector antenna includes a reflector and a distributed feed array. The reflector has a portion with a dual parabolic shape. The distributed feed array transmits and receives a plurality of electromagnetic energy beams simultaneously, and is positioned adjacent the reflector so that the reflector reflects the transmitted and received electromagnetic energy beams. The distributed feed array is offset from the reflector so that a plane wave formed by the transmitted electromagnetic energy beams reflected by the reflector will not substantially impinge the distributed feed array. The antenna also has a beam switching network which is a hybrid network for selectively actuating separate but overlapping portions of the distributed feed array to produce two transmit elevation beams.

Laser ultrasonic detection method and apparatus therefor

Abstract: A reflector/vibrator plate is irradiated with an ultrasonic generation laser beam to generate an ultrasonic wave therein, and the thus generated ultrasonic wave is transmitted into an object to be inspected. The ultrasonic wave transmitted into the inspection object returns to the reflector/vibrator plate by being reflected by a defect such as a flaw present inside the inspection object, if any, thereby causing a vibration in the reflector/vibrator plate. By detecting this vibration with an ultrasonic detection laser beam, the presence of the defect is detected and located in the inspection object. The ultrasonic flaw detection method can be applied to a variety of inspection objects including reflectors having irregularities on the surface or a poor reflectivity, inspection objects having on the surface thereof an opaque liquid which will not allow transmission of the laser beam therethrough, and inspection objects which do not permit generation of ultrasonic waves with a laser beam.

Interferometer spectrometer having tiltable reflector assembly and reflector assembly therefor

Abstract: A twin-arm interferometer spectrometer having a tiltable reflector assembly, which includes a pair of mutually facing parallel reflective elements, varies the path length of both interferometer arms simultaneously to achieve high resolution in a small, low maintenance design. Collimated electromagnetic radiation is split by a beamsplitter into first and second arm beams. Both arm beams impinge on the tiltable reflector assembly, to retroreflectors, and back to the beamsplitter wherein they recombine to form an exit beam. The exit beam is directed to a sample and then to a suitable detector. Modulation of the exit beam is produced by tilting the reflector assembly about an axis parallel to the reflective elements in the reflector assembly. This tilting causes a simultaneous variation in the path length of both interferometer arms, and thereby yields a large total path difference with a relatively small movement. Symmetry between the paths of the reference beam and test beam results in greater stability and greater immunity to thermal expansion.

Lighting device with dichroic reflector

Abstract: Lighting device comprising a lighting bulb arranged inside a reflector produced from a transparent material and possessing a selective reflecting surface (4) capable of reflecting the visible radiation coming from the bulb (2), while allowing the heat radiation to pass through it, while on the outside of this reflector there is a reflecting surface (6, 8) for the heat radiation passing through the reflector (1), the device being characterized in that the reflecting surface (8) for the heat radiation is formed on a supporting piece arranged outside the reflector.

Compact range reflector analysis using the plane wave spectrum approach with an adjustable sampling rate

Abstract: An improved method for determining the test zone field of compact range reflectors is presented. The plane wave spectrum (PWS) approach is used to obtain the test zone field from knowledge of the reflector aperture field distribution. The method is particularly well suited to the analysis of reflectors with a linearly serrated rim for reduced edge diffraction. Computation of the PWS of the reflector aperture field is facilitated by a closed-form expression for the Fourier transform of a polygonal window function. Inverse transformation in the test zone region is accomplished using a fast Fourier transform (FFT) algorithm with a properly adjusted sampling rate (which is a function of both the reflector size and the distance from the reflector). The method is validated by comparison with results obtained using surface current and aperture field integration techniques. The performance of several serrated reflectors is evaluated in order to observe the effects of edge diffraction on the test zone fields. >

Effect of an arcjet plume on satellite reflector performance

Abstract: The effect of an arcjet plume on the performance of satellite reflector antennas is studied. The arcjet plume is modeled as a weakly ionized plasma. The spatial permittivity distribution of the plume is approximated using the measured electron density profile and a cold plasma model. Geometrical optics is applied to determine the ray paths as well as the transmitted fields through the inhomogeneous plume. The ray optics results are compared against several exact solutions for scattering from inhomogeneous dielectrics, and good agreement is observed for sufficiently large scatterer size. The far-field antenna patterns of the reflector in the presence of the plume are calculated from the transmitted ray fields using a ray-tube integration scheme. For arcjet prototypes in the 1-kW class, the plume effect on the antenna performance is small. As the electron density increases, the main beam and sidelobe level gradually degrade. The main beam also tends to squint away from the plume region. >

Lens-Type Compact Antenna Test Range at MM-Waves

Abstract: A lens-type compact antenna test range (CATR) has been studied both theoretically and experimentally. For a lens with low dielectric constant ?r, the surface accuracy requirement is much less stringent than for a reflector. An experimental CATR with a shaped polyethylene (?r, = 2.32) lens was made at 110 GHz. In order to make the amplitude ripple in the quiet zone small, the use of saw tooth serrations around the lens was studied. Theoretically the quiet zone field is exellent (peak to peak ripple 0.27 dB). Preliminary measured values are promising (peak to peak ripple 2.0 dB).