Showing papers on "Reflector (antenna) published in 1998"

A Dielectric Omnidirectional Reflector

Abstract: A design criterion that permits truly omnidirectional reflectivity for all polarizations of incident light over a wide selectable range of frequencies was used in fabricating an all-dielectric omnidirectional reflector consisting of multilayer films. The reflector was simply constructed as a stack of nine alternating micrometer-thick layers of polystyrene and tellurium and demonstrates omnidirectional reflection over the wavelength range from 10 to 15 micrometers. Because the omnidirectionality criterion is general, it can be used to design omnidirectional reflectors in many frequency ranges of interest. Potential uses depend on the geometry of the system. For example, coating of an enclosure will result in an optical cavity. A hollow tube will produce a low-loss, broadband waveguide, whereas a planar film could be used as an efficient radiative heat barrier or collector in thermoelectric devices.

Electrochromic rearview mirror incorporating a third surface metal reflector

Abstract: An EC variable reflectance mirror (110) for a vehicle includes a reflector/electrode (120) on the third surface (114a) of the mirror. This reflector/electrode forms an integral electrode in contact with the electrochromic media, and may be a single layer of a highly reflective material or may comprise a series of coatings.

Dual reflector microwave antenna

Abstract: A dual-reflector microwave antenna comprises the combination of a paraboloidal main reflector having an axis; a waveguide and dual-mode feed horn extending along the axis of the main reflector, a subreflector for reflecting radiation from the feed horn onto the main reflector in the transmitting mode, and a shield extending from the outer edge of the main reflector and generally parallel to the axis of the main reflector, the inside surface of the shield being lined with absorptive material for absorbing undesired radiation. The subreflector is shaped to produce an aperture power distribution that is substantially confined to the region of the main reflector outside the shadow of the subreflector. The support for the subreflector is preferably a hollow dielectric cone having a resonant thickness to cause energy passing through said cone to be in phase with energy reflected off of said cone so as to achieve phase cancellation.

Electromagnetic radiation emitting or receiving assembly

Abstract: An electromagnetic radiation emitting assembly is disclosed and which includes a supporting substrate having opposite first and second surfaces and having an area formed therein which allows electromagnetic radiation to pass therethrough; a reflector positioned adjacent to the second surface of the substrate and oriented in a given position relative to the area formed in the substrate; and an electromagnetic radiation emitter mounted on the second surface of the substrate and which emits a source of electromagnetic radiation which is reflected by the reflector through the area formed in the supporting substrate An electromagnetic radiation receiver is also described

High numerical aperture optical focusing device having a conical incident facet and a parabolic reflector for use in data storage systems

Abstract: An optical focusing device for focusing an incident optical beam onto a focal plane, as a focal spot. The optical focusing device includes an incident central refractive facet upon which an optical beam impinges, and a high-index glass body through which the incident optical beam passes toward a bottom reflective surface. The bottom reflective surface reflects the optical beam through the body, toward a peripheral reflector. The peripheral reflector focuses the optical beam toward a focal plane on which the focal spot is formed. The focal plane is defined within a pedestal that forms part of the optical focusing device, and that extends from the bottom reflective surface. The central facet is conically shaped for refracting the incident optical beam away from the pedestal, onto the bottom reflective surface. The peripheral reflector surrounds the central facet and can have various appropriate shapes, such as an aspherical shape or a tilted parabolic shape, which compensates for the conical factor and aberrations introduced by the central facet. The top surface includes the central facet and the peripheral facet, and can be made substantially flat using diffractive optical elements or Fresnel optics.

Orthogonal mode junction (OMJ) for use in antenna system

Abstract: A multiple beam antenna system including a reflector that is at least partially parabolic in one dimension, a pair of dielectric lenses, and a pair of waveguides. Multiple received beams are received and reflected by the reflector into an orthogonal mode junction which separates signals of a first polarity from signals of a second orthogonal polarity. The signals of the first polarity are forwarded into a first waveguide and the orthogonal signals of the second polarity are forwarded into a second parallel waveguide. A plurality of satellites may be accessed simultaneously thus allowing the user to utilize both signals at the same time. In certain embodiments, each of the dielectric lenses may be of the bifocal type.

Method and apparatus for directional measurement of subsurface electrical properties

Abstract: A directional induction logging tool is provided for measurement while drilling. This tool is preferably placed in a side pocket of a drill collar, and it comprises transmitter and receiver coils and an electromagnetic reflector. The reflector, which may be a layer of highly conductive material placed between the coils and the body of the drill collar, serves to focus the electromagnetic fields generated and sensed by the tool in the direction away from the reflector, thus providing a directional response to formation conductivity with a relatively high depth of investigation. In preferred embodiments of the invention, magnetically permeable cores are placed within the coils to concentrate the magnetic fields that pass through them. Circuitry is described for balancing the mutual inductive coupling of the coils by injecting a direct current signal through one or more of the coils, which alters the magnetic permeability of the core material. The magnitude of the direct current required to achieve a balanced condition may be derived from the quadrature phase component of the return signal. Circuitry is also provided for generating a transmitted signal and for processing the return signals, including digital-to-analog conversion circuitry for providing digital data for transmission to the surface. This tool may be employed to provide real-time directional conductivity information that may be used to detect and follow bed boundaries in geosteering operations.

Coherent reflectometric fiber Bragg grating sensor array

Abstract: A fiber optic sensor array has multiple segments, each capable of detecting a physical condition such as an acoustic wave. The segments are separated by weak reflectors such as fiber optic Bragg gratings. Light from a light source is input into the input end of the array. Light reflected by each of the reflectors has a phase shift representing the effects of the physical condition on all of the segments from the input end to that reflector. To address a specific reflector, the return light is demultiplexed. This demultiplexing is done by modulating the light input into the input end of the array with a pseudo-random bit sequence and correlating the output with a time-shifted version of the pseudo-random bit sequence to isolate the part of the output caused by that reflector. To address a specific segment, the phase shifts from two adjacent reflectors are determined. The return light can be strengthened by mixing it with a portion of the light picked off from the light source.

100% efficient narrow-band acoustooptic tunable reflector using fiber Bragg grating

Abstract: This paper reports a 100% efficient Bragg-grating-based acoustooptic superlattice modulator in a fiber whose diameter is reduced by HF etching. The acoustically induced reflections, which appear on both sides of the Bragg stop-band, are tunable by altering the acoustic frequency, and have bandwidths corresponding to weak versions of the permanent Bragg grating. These unique properties may lead to important applications in, e.g., reconfigurable wavelength division multiplexing, Q-switching, amplitude modulation, and frequency shifting.

Neuro-navigation system for surgery

Abstract: The neuro-navigation system uses a reflector referencing system for neurosurgical instruments and treatment devices, an IR radiation source, at least two referencing cameras (14), coupled to a processor (11) with a graphical image screen display monitor (12) and a number of reflectors. Selected reflectors with characteristic reflection characteristics are removably attached to the neurosurgical instruments or treatment devices via corresponding adapters.

Multilayer reflector with selective transmission

Abstract: In a multilayer dielectric reflector, treating the surface of the reflector selectively increases the amount of light transmitted through the reflector. Various surface treatments can be used to permit light to transmit through the reflector that would otherwise be reflected by the reflector. In one such reflector, different portions of the surface have different coupling efficiencies for coupling light having a high propagation angle into the multilayer reflector. Those portions having higher coupling efficiencies on each side of the reflector have a higher degree of transmission.

Flash tube reflector with arc guide

Abstract: A combined reflector and arc guide for use with a xenon flash tube comprises a reflector structure having a reflecting surface that is adapted to be placed in a predetermined orientation with respect to the flash tube. An electrically conductive arc guide is carried by, and is preferably integral with, the reflector structure for controlling the arc in the flash tube. The arc guide comprises an elongated ridge that projects outwardly from the reflecting surface of the reflector structure, and extends in a direction substantially parallel to the longitudinal axis of the flash tube. An electrical terminal is carried by the reflector structure and has an electrical connection to the arc guide for allowing an electrical potential to be applied to the arc guide. The reflector structure is preferably made of an electrically conductive plastic material, thereby providing continuity between the electrical terminal and the arc guide without the need for a separate conductor. An area of modified reflectivity, preferably in the form of a plurality of grooves, may be provided in the reflective surface of the reflector structure to spread out the intensity peak of the flash tube. The disclosed reflector is simple and inexpensive to manufacture, and is suited for use in automated hematology systems in which a pulse of light from the flash tube causes dyed blood cell layers in a capillary tube to fluoresce so that a complete blood count can be obtained by optical imaging techniques while the blood sample is being rotated in a centrifuge.

Designing axially symmetric Cassegrain or Gregorian dual-reflector antennas from combinations of prescribed geometric parameters

Abstract: A procedure to design axially symmetric Cassegrain or Gregorian dual-reflector antennas from various combinations of prescribed geometric parameters is presented. From these input parameters, the overall geometry of the antenna is derived in closed form. This procedure can be used as the starting point of a synthesis procedure, where both main reflector and subreflector are shaped to create the desired aperture field distribution.

The beam pattern of the IRAM 30-m telescope (a reflector with several surface error distributions)

Abstract: Total power scans across the Moon around New Moon (mostly day time) and Full Moon (night time) at 3.4 mm (88 GHz), 2.0 mm (150 GHz), 1.3 mm (230GHz), and 0.86 mm (350 GHz) wavelength are used to derive the beam pattern of the IRAM 30-m telescope to a level of approximately -30 dB(0.1%) and, dependent on wavelength, to a full width of 1000 - 1400''. From the reflector surface construction and application of the antenna tolerance theory we find that the measurable beam consists of the diffracted beam, two underlying error beams which can be explained from the panel dimensions, and a beam deformation mostly due to large-scale transient residual thermal deformations of the telescope structure. In view of the multiple beam structure of the 30-m telescope, and of other telescopes with a similar reflector construction of (mini-)panels and panel frames, we summarize the antenna tolerance theory for the influence of several independent surface/wave front deformations. This theory makes use of different correlation lengths, which in essence determine the independent error distributions, and of the wavelength-scaling of the diffracted beam and of the error beams. From the Moon scans we derive the parameters for calculation of the 30-mtelescope beam in the wavelength range 3 mm to 0.8 mm as required for the reduction of astronomical observations, in particular of extended sources. The parameters of the beam are primarily for the time after July 1997 when the reflector was re-adjusted and improved to the illumination weighted surface precision of sigma _T = 0.065 - 0.075 mm.In the Appendix we explain the choice for this analysis of scans taken around New Moon and Full Moon.

Method and apparatus for accurately positioning a tool on a mobile machine using on-board laser and positioning system

Abstract: A method and apparatus for accurately positioning a tool on a mobile machine are provided. The machine is equipped with a satellite positioning system (SPS) receiver, a robotic total station with an integrated scanning laser and a storage facility storing a digital terrain model (DTM) of a work area. The machine operates within the work area and a number of stationary reflectors are positioned at various locations about the work area. The SPS receiver determines the current location of the machine. A system controller then references the DTM to determine the closest stationary reflector to the current location of the machine. Location data of the closest reflector is then provided to the robotic total station, which locates the closest reflector. The scanning laser then locks on to the reflector and the system controller determines the angle between the laser and the reflector. Based upon a computed angle, a displacement between the actual elevation of the machine and the design elevation for the current location of the machine is computed. The position of the tool is then adjusted based upon the computed displacement. If the closest reflector is out of range or obstructed by another object, the onboard system automatically determines the next closest reflector.

Wavelength multiplexed light transfer unit and wavelength multiplexed light transfer system

Abstract: A branch circuit is formed by forming an optical filter by means of connecting a wavelength selective reflector to between two units of directional coupler and further assembling three units of the optical filter. In the branch circuit, the three optical filters are connected to each other so that the light coming in from a first optical filter is outputted to a third optical filter when the wave length selective reflector reflects the light, and to a second optical filter when the wavelength selective reflector passes the light therethrough; the light coming in from the second optical filter is outputted to the first optical filter when the wavelength selective reflector reflects the light, and to the third filter when the wavelength selective reflector passes the light therethrough; and also the light coming in from the third optical filter is outputted to the second optical filter when the wavelength selective reflector reflects the light and to the first optical filter when the wavelength selective reflector passes the light therethrough.

High-finesse disk microcavity based on a circular Bragg reflector

Abstract: We made disk-shaped microcavities of approximately 10 μm2 in area in a GaAs/AlGaAs waveguide structure by etching deep vertical concentric trenches. The trenches form a circular Bragg-like reflector that confines light in the remaining two lateral dimensions. We demonstrate from photoluminescence excited in the waveguide the confinement of discrete disk modes whose wave vector is mainly radial, in contrast with whispering gallery modes. Their quality factors up to Q=650 indicate in-plane reflectivities approaching 90%. In the near infrared, this represents a demonstration of wavelength-scale light confinement based on photonic crystal effects in two dimensions.

Device for generating acoustic shock waves, especially for medical applications

Abstract: A device for generating acoustic shock waves, comprising at least two electrodes which form a spark discharge gap G in a fluid volume and a reflector for the acoustic shock waves generated during the spark discharge made of an electrically conductive material, and wherein the power to one of the electrodes is supplied by way of the reflector.

Compact wireless transceiver board with directional printed circuit antenna

Abstract: A wireless transceiver includes a dielectric substrate having first and second major surfaces on which an RF circuit and a baseband processing circuit are mounted, and a printed circuit antenna formed on the substrate. The printed circuit antenna has at least one director formed by strip conductors disposed on the substrate, a reflector formed by the edge of a ground area disposed on the substrate, and a dipole formed by strip conductors on the substrate. The dipole is positioned between the reflector and the director. An antenna with this low profile and compact antenna structure has high directivity.

Reflector-provided dipole antenna

Abstract: To realize a reflector-provided dipole antenna showing an outstanding performance in a wide frequency range and allowing simultaneous transmission and reception at different frequencies. A dipole antenna element is provided at the back of a dielectric substrate set to the reflector surface. A parasitic element is provided on the front of the dielectric substrate, which is constituted by forming and protruding the central portion of a linear conductor forward like an almost trapezoidal shape, setting the pyramidal protruded portion to a position corresponding to the front of the feed point of the dipole antenna element and the both parts of the said parasitic element towards ends to positions corresponding to the rear of the dipole antenna element. A feed circuit provided on the face side of dielectric substrate is connected to a coaxial connector provided at the back of the reflector.

Three-reflection collection system for solar and lunar radiant energy

Abstract: A system utilizing a series of three mirrors for purposes of collecting, concentrating, collimating and distributing radiant flux, such as sunlight or moonlight. The system generally includes a first parabolic reflector having a hole formed centrally therethrough, a second parabolic reflector slightly smaller in diameter than the hole formed through the first reflector and attached in spaced relation thereto, such that the two reflectors share a common optical axis, and a third, planar reflector. A structural framework supports the three reflectors and includes a light pipe, or other light distributing channel, through which the collected light is sent. First and second motors actuate gear assemblies attached to the framework to cause the reflectors to track both the elevation and azimuth angles, respectively, of the sun and/or moon. One microprocessor operatively attached to position sensor assemblies incorporated into each of the motors, sends elevation and azimuth angle data to the sensors at predetermined intervals throughout each day, ultimately causing the motors to continuously adjust the position of the reflectors such that the first and second reflectors' optical axis is perfectly aligned with the elevation and azimuth angle of the sun, or moon, thereby maximizing the system's potential collection of radiant flux.

A retrodirective microstrip antenna array

Abstract: A Van Atta retrodirective reflector was designed and developed, using an aperture-coupled microstrip antenna array. This reflector possesses the advantage of reflecting high fields to the source point over a wide range of incidence angles and, owing to the low cost and conformability of the structure, is suitable for applications in intelligent vehicle highway systems (IVHS). An approximate theory associated with the reradiation and scattering principles of the reflector is presented for the purpose of understanding and designing the reflector. The utility of the retrodirective reflector was demonstrated by comparison with a plate reflector and a microstrip antenna array without a feed structure. Finally, a reflector with switches in the middle of the microstrip feed lines was investigated for possible applications in communications and remote identification.

Buried reflectors for light emitters in epitaxial material and method for producing same

Abstract: A buried reflector 50 in an epitaxial lateral growth layer forms a part of a light emitting device and allows for the fabrication of a semiconductor material that is substantially low in dislocation density. The laterally grown material is low in dislocation defect density where it is grown over the buried reflector making it suitable for high quality optical light emitting devices, and the embedded reflector eliminates the need for developing an additional reflector.

Mean-field theory of two-dimensional metallic photonic crystals

Abstract: Metallic photonic crystals have gaps starting from the null frequency They can be used as antenna substrates Using two computer codes based on rigorous scattering theories, we investigate the properties of nondoped and doped two-dimensional metallic photonic crystals We show numerically that such a structure can simulate a material that has a plasmon frequency in the microwave domain Below this frequency the crystal is opaque and acts as a good reflector These calculations confirm both a conjecture made by specialists in solid-state physics and mathematical considerations developed by specialists in limit analysis

Reflector for distance measurement

Abstract: A reflector is used with an electric distance meter, for measuring a distance of two positions. The reflector includes a reflecting member which reflects an incident light in parallel to the direction of incidence, and a selective transmission member provided to a light-incident surface of the reflecting member. The selective transmission member allows infrared ray to pass, while the selective transmission member prevents visible light from passing.

Integrated hybrid silicon-based micro-reflector

Abstract: A light reflective device including an insulative substrate; a silicon wafer positioned over the insulative substrate and defining an opening and having a flexible beam portion having top and bottom surfaces which extend into the opening; a layer of ferromagnetic material formed over the top surface of the flexible beam portion; a reflector formed over the ferromagnetic layer on the top surface of the flexible beam portion; and a micro-electromagnet mounted on the insulative substrate relative to the opening of the silicon wafer and adapted to produce a magnetic field in response to an applied current which acts on the ferromagnetic layer to cause the bending of the flexible beam portion, ferromagnetic layer and reflector.

Piezoceramic actuated aperture antennae

Abstract: Recently, it has been demonstrated that aperture antennae can have their performance improved by employing shape control on the antenna surface. The antennae previously studied were actuated utilizing polyvinylidene fluoride (PVDF). Since PVDF is a polymer with limited control authority, these antennae can only be employed in space based applications. This study examines more robust antenna structures devised of a thick metalized substrate with surface bonded piezoceramic (PZT) actuators. In this work, piezoceramic-actuated adaptive antennae of cylindrical-cut shape are studied. When a PZT actuator is attached to the reflector surface, the converse effect develops a bending moment in the structure making the reflectors bend inward or outward. This bending can be employed in antenna beam steering and shaping. In order to effectively construct the antenna, the piezoceramic-actuated antenna surface was modeled using classical curved beam theory and Newton's method. The deflection versus voltage relationship was then experimentally verified, and the resulting far-field radiation pattern was simulated on computer. The results emphasize two major points: firstly, the far-field radiation pattern can be altered in a positive fashion, and secondly the first two radiation modes of the antenna correspond to the first vibration mode shapes of the structure.

Dual reflector lighting system

Abstract: A dual reflector lighting system having an adjusting assembly for independently adjusting an inner reflector (24) and an outer reflector (31) relative to a gaseous discharge lamp (14). The lighting system includes a housing (12) having a ballast assembly mounted therein. An elongated tubular adjusting member (18) has one end thereof connected to the bottom of the housing. A lamp socket (16) for receiving a gaseous discharge lamp (14) is mounted to the other end of the adjusting member (18). The lamp socket (16) is electrically connected to the ballast assembly. The system includes both an outer reflector (31) and an inner reflector (24) mounted coaxially about the gaseous discharge lamp (14). The outer reflector (31) is mounted to the tubular adjusting member (18) for movement relative to adjust the outer reflector (31) relative to the gaseous discharge lamp (14). The inner reflector (24) is connected to the adjusting member (18) for adjusting the inner reflector (24) relative to the gaseous discharge lamp (14).

Liquid crystal display with corrugated reflective surface

Abstract: A reflective type liquid crystal display of this invention comprises a reflector member having corrugated surface stored therein; an overcoat layer formed on the corrugated surface of the reflector member for making the corrugated surface flat; and a color filter layer formed on the overcoat layer, and wherein a thickness of the overcoat layer is more than twice of a depth of the concave part in the corrugated surface of the reflector member.

Analysis and characterization of multilayered reflector antennas: rain/snow accumulation and deployable membrane

Abstract: There are important engineering issues in designing reflector antennas that cannot be addressed by simply assuming a perfect electric conductor (PEC) reflector surface For example, coatings may exist on antenna surfaces for protection, rain or snow can accumulate on outdoor reflectors, and the deployable mesh or inflatable membrane antennas usually do not have solid PEC reflector surfaces Physical optics (PO) analysis remains the most popular method of reflector analysis owing to its inherent simplicity, accuracy, and efficiency The conventional PO analysis is performed under the assumption of perfectly conducting reflector surface To generalize the PO analysis to arbitrary reflector surfaces, a modified PO analysis is presented Under the assumptions of locally planar reflector surface and locally planewave characteristic of the waves incident upon the reflector surface, the reflection and transmission coefficients at every point of the reflector surface are determined by the transmission-line analogy to the multilayered surface structure The modified PO currents, taking into account by the finite transmissions of the incident waves, are derived from the reflection and transmission coefficients Applications on the analyses of the rain and snow accumulation effects on the direct-broadcast TV antennas and the effects of finite thickness and finite conductivity of the metal coating on a 15-m inflatable antenna are described and results are presented