Showing papers on "Reflector (antenna) published in 1992"

Recessed lighting fixture

Abstract: A lighting fixture having a simplified structure is provided with such benefits as a junction box attached either permanently or releasably to the housing, a full reflector for improved optics, and support means for installation in different ceiling structures. The reflector is positionable within the housing, whereby inexact or inaccurate mounting of the housing to the ceiling structure can be corrected by changing the orientation of the reflector. Also provided are novel junction boxes. In various embodiments, the junction box may contain an L-shaped door, to cover an L-shaped opening which allows the interior of the junction box to be inspected from the bottom after installation. Another embodiment of junction box includes side walls flexibly joined to permit installation and removal of the junction box. Preferably, this latter embodiment is installed in a fixture through the bottom opening through which the reflector, socket, bulb, and the like are installed.

High frequency techniques for antenna analysis

Abstract: A summary of various high-frequency techniques is presented for analyzing the electromagnetic radiation from antennas in the presence of their host environment. These techniques provide physical insight into antenna radiation mechanisms and are found to be highly efficient and accurate for treating a variety of practical antenna configurations. Examples to which these techniques have been applied include open-ended waveguide antennas, horn and reflector antennas, and antennas on aircraft and spacecraft. The accuracy of these techniques is established via numerical results which are compared with those based on other independent methods or with measurements. These high frequency methods can be combined with other techniques, through a hybrid scheme, to solve an even greater class of problems than those which can be solved in an efficient and tractable manner by any one technique alone. >

Optical systems with grating reflector

Abstract: Optical systems including an optical amplifier and a narrow bandwidth optical filter for removing undesired spontaneous emission. An in-fiber Bragg grating reflector reflects substantially only the input amplified signal back to a circulator port of an optical circulator where the desired amplified signal is coupled from the next circulator port. The undesired emission exits from the grating reflector and is removed from the system. Cascaded grating reflectors are used in a wavelength division multiplexing (WDM) system. A two section narrow band transmission filter with cascaded gratings.

Electrostatically tunable optical device and optical interconnect for processors

Abstract: A microlaser is described which is electrostatically tunable. One of the reflectors includes at least one reflecting part whose distance from the other reflector can be adjusted to change the effective optical distance between the reflectors and thus tune the optical frequency at which lasing occurs. The disclosure brings out that the inventive aspect is also applicable to other optical devices having reflectors defining a Fabry-Perot cavity. An optical interconnecting scheme for processors using the microlaser is also described.

Liquid crystal display device having reflector of a substrate, a patterned resin, and a reflective film, and method of making same

Abstract: A reflective liquid crystal display device comprising a reflector with a number of small convex portions of the same shape is provided. The reflector is formed by patterning a photosensitive resin applied to one surface of a core substrate to a predetermined pattern so as to form a number of small convex portions, heat-treating the surface having the convex portions, and covering the surface with a reflective film. By suitably selecting the shape of the convex portions, the reflective properties of the reflector are controlled.

Bragg reflectors

Abstract: A Bragg reflector composed of periodic cylindrically symmetric corrugations can provide a reflection of nearly unity through the principles of constructive interference, allowing the formation of a frequency selective resonator. Mode conversion will occur, but can be reduced by tapering the amplitude of the corrugations. Reflection measurements are compared with theoretical predictions for untapered sinusoidal and rectangular corrugation as well as a reflector tapered according to the Hamming-window prescription. Measurements of Bragg resonators are also presented. >

Satellite-tracking millimeter-wave reflector antenna system for mobile satellite-tracking

Abstract: A miniature dual-band two-way mobile satellite-tracking antenna system mounted on a movable vehicle includes a miniature parabolic reflector dish having an elliptical aperture with major and minor elliptical axes aligned horizontally and vertically, respectively, to maximize azimuthal directionality and minimize elevational directionality to an extent corresponding to expected pitch excursions of the movable ground vehicle. A feed-horn has a back end and an open front end facing the reflector dish and has vertical side walls opening out from the back end to the front end at a lesser horn angle and horizontal top and bottom walls opening out from the back end to the front end at a greater horn angle. An RF circuit couples two different signal bands between the feed-horn and the user. An antenna attitude controller maintains an antenna azimuth direction relative to the satellite by rotating it in azimuth in response to sensed yaw motions of the movable ground vehicle so as to compensate for the yaw motions to within a pointing error angle. The controller sinusoidally dithers the antenna through a small azimuth dither angle greater than the pointing error angle while sensing a signal from the satellite received at the reflector dish, and deduces the pointing angle error from dither-induced fluctuations in the received signal.

Optical identification friend-or-foe

Abstract: An identification friend-or-foe system for vehicles wherein each vehicle is provided with a radiation transmitter and a receiver with a detector for detecting radiation transmitted by other vehicles. Each transmitter can transmit a first coded signal which can be detected by the receivers in other vehicles, the receivers providing an unblocking signal after the first coded signal is correctly identified. The unblocking signal clears a radiation transmission path in the vehicle, the path containing a reflector which reflects the received signal back to the source of the transmission. The reflector adds a further predetermined code to the signal reflected from the reflector with each vehicle having another detector for detecting a reflected signal and a device to identify the further predetermined code.

Rangefinder with fast multiple range capability

Abstract: A rangefinder is described that uses the propagation time of a beam of infrared radiation to measure distances of up to 120 m with errors of less than 50 μm. The instrument is capable of measuring up to five different distances per second by directing an amplitude modulated infrared beam to a retroreflector located at the far end of each path. The instrument is being tested with the expectation that such a system could be used to make precise and rapid measurements on a large radio telescope. Such measurements would be used to adjust the shape of the telescope reflector surface to correct for thermal and gravitational deformations taking place during astronomical observations. It is possible that the measuring system could be extended to relate the positions of certain moving parts of the structure to a reference system fixed in the ground, thus opening the possibility of making corrections to the telescope pointing.

Electromagnetic-Wave Propagation in Unmagnetized Plasmas

Abstract: : This final report describes an investigation of electromagnetic-wave propagation in unmagnetized plasmas and its application to the reduction of the radar cross section (RCS) of a plasma-filled enclosure We have demonstrated RCS reduction of 20 to 25 dB with a prototype system at the radar range at Hughes Aircraft's Microwave Products Division in Torrance The prototype consists of a sealed ceramic enclosure with a microwave reflector and a plasma generator inside it When the plasma is present, the RCS is significantly reduced over a frequency range of 4 to 14 GHz As part of the program, we also investigated the basic-plasma-physics issues relating to the absorption and refraction of electromagnetic (EM) waves in collisional plasmas We demonstrated absorption as high as 63 dB in a section of plasma-loaded C-band rectangular waveguide We also developed a theoretical model for the plasma cloaking process that includes scattering contributions from the plasma-vacuum interface, partial reflections from the plasma, and collisional absorption in the plasma The theoretical model is found to be in reasonable agreement with the experimental results and can be used to confidently design future plasma cloaking systems Plasma Cloaking, RCS Reduction

Self-monitoring semiconductor laser device

Abstract: The present invention is a semiconductor laser having an integral photodiode and/or modulator. The integrated structure comprises a quantum well active region sandwiched between a pair of distributed Bragg reflector stacks for emitting laser light transverse to the planes of growth. An intrinsic layer and a doped semiconductor layer are disposed on one of the reflector stacks for forming, in combination with the outer layer of the stack, a photodiode in the path of emitted light. The diode can be used either to monitor the laser power or to modulate the laser output. The device is particularly suited for fabrication and testing in large arrays and, in addition, has the advantages of a circular, low divergence optical output, inherently single mode operation, and a high two-dimensional packing density.

Bent crystal, bent multilayer optics on a multipole wiggler line for an x-ray diffractometer with an imaging plate detector

Abstract: A setup for diffraction and diffuse scattering studies on biological crystals, in the wavelength range 1.5–0.9 A, is operating on the superconducting wiggler line of the storage ring DCI at LURE. Double focusing and rejection of harmonic contribution are achieved by combining two Bragg reflectors with elliptical curvature, respectively, a Si or Ge single crystal and a large W/Si interferential reflector (layered synthetic microstructure). Area detectors include photographic films and an imaging plate scanner device.

Beam delivery system for corneal surgery

Abstract: An apparatus and method for delivering radiant energy beams onto an area of a cornea in a line focus to create a linear incisions. The radiant energy beams may be focused in a linear configuration onto the external surface of the cornea or onto intrastromal areas of the cornea of an eye to ablate the cornea in a radial slot, circumferential curved slot, or lenticular pattern, and thereby modify its curvature and refractive power. The apparatus includes an array of central reflectors and an assembly of peripheral reflectors. Each central reflector is associated with a respective peripheral reflector so that a beam reflected by the central reflector is intercepted by its associated peripheral reflector and is again reflected to precisely incise either external or internal areas of the cornea. Each peripheral reflector has a curved reflective surface to provide a line focus on the cornea, including both rectilinear and curvilinear line focus to create radial and circumferential curved incisions. In a modified embodiment, the assembly of peripheral reflectors and the array of central reflectors rotate to permit lathing of the cornea.

Lamp/reflector assembly and electric lamp for use therein

Abstract: A lamp/reflector assembly has an electric lamp (10) having a base (13) presenting projections (17-19) which touch an imaginary sphere having its center of curvature coincident with the electrical element (12) of the lamp. The reflector (1) of the assembly has an opening (6) through which the lamp (10) extends, and a convex, spherically curved mounting surface (30) aligned with respect to the opening (6). The mounting surface (30) has its center of curvature substantially coincident with the optical center (4) of the reflector (1). The projections (17-19) of the base bear against the mounting surface (30) and the optical center (4) of the reflector (1) coincides with the electrical element (12), also when the lamp occupies one of a number of positions tilted with respect to the optical axis (3) of the reflector (1).

Millimeter-wave double-dipole antennas for high-gain integrated reflector illumination

Abstract: A double-dipole antenna backed by a ground plane has been fabricated for submillimeter wavelengths. The double-dipole antenna is integrated on a thin dielectric membrane with a planar detector at its center. Measured feed patterns at 246 GHz agree well with theory and demonstrate a rotationally symmetric pattern with high coupling efficiency to Gaussian beams. The input impedance is around 50 Omega and will match well to a Schottky diode or SIS detector. The double-dipole antenna served as the feed for a small machined parabolic reflector. The integrated reflector had a measured gain of 37 dB at 119 mu m. This makes the double-dipole antenna ideally suited as a feed for high-resolution tracking or for long-focal-length Cassegrain antenna systems. >

LCD display with microtextured back reflector and method for making same

Abstract: Applicant has discovered a method for microembossing reflector surfaces with controlled reflecting patterns too small to be resolved by the unaided eye but capable of providing controlled reflection characteristics superior to uncontrolled random deformation. The result is a microtextured reflector of having dispersion characteristics of enhanced uniformity and a display device which can be read over an enhanced range of viewing angles. Specifically, a reflector in accordance with the invention comprises a base plane and a pattern of microelements (11,12) having maximum lateral dimensions less than 125 micrometers and smooth, continuous mold-formed surfaces arising from the base plane. Such a reflector surface can be made using a master formed by covering a substrate with photoresist, exposing the resist to define a pattern of microelements having maximum lateral dimensions less than about 125 micrometers and heating the substrate to partially melt the resist elements thereby obtaining smooth-surfaced microelements. The master can be used to form an embossing surface or mold, which, in turn, can be used to make a microtextured reflecting surfaces. A preferred reflecting surface is composed of closely packed, smooth-surfaced spherical segments (11) having diameters of twenty-five microns, altitudes of four microns. Advantageously random segments (12) are disposed between successive spherical segments. The preferred reflector possesses reflecting characteristics superior to conventional isotropic reflectors.

Composite back reflector for photovoltaic device

Abstract: A back reflector for a photovoltaic device includes an electrically conductive, textured layer and a reflective layer conformally disposed on the textured layer. The reflector may include a protective layer atop the reflective layer. The materials of the reflector are selected to be non-reactive under conditions encountered in the manufacture and use of the photovoltaic device.

Staggered helical array antenna

Abstract: An antenna composed of an array of helical radiators has, in accordance with a methodology of the invention, a physical structure for reducing mutual coupling between closely spaced radiators so as to permit a reduction in spacing of the radiators. The radiators are mounted upon a mounting base, such as a ground plane element, with the helical radiators extending forward of the mounting base. Distances between the radiators and the mounting base are staggered in an amount approximately equal to one turn of a helix. The stagger distance corresponds approximately to one quarter of a free-space wavelength. The staggering significantly reduces the mutual coupling so as to permit closer spacing of the helical radiators such as, by way of example, in the formation of a feed directing radiant energy to a reflector of the antenna.

Multi-spectral seeker antenna

Abstract: A multi-spectral seeker system for detecting radiation in the infrared (IR) band and a plurality of radio frequency (RF) bands suitable for use in a guided missile is disclosed. The IR and RF seekers are coaxially integrated on a single gimbaled platform and share a common aperture without significant performance degradation. In the preferred embodiment, the IR seeker uses a Cassegrainian reflector assembly with surfaces reflective to IR but transparent to RF signals. The first RF seeker uses a resonant dichroic reflector antenna which is transparent to RF signals at frequencies no closer than 0.5 octaves from the dichroic reflector system operating frequency. The second RF seeker may use any suitable RF antenna system although a planar-array of multi-mode spiral antennas or a standard flat plate slotted array are preferred. The second RF seeker may operate in an active, semi-active, or passive mode. The IR seeker means and both RF seeker means together provide coaxial seeking in a single aperture covering three frequency bands without significant loss of performance in the RF antenna and IR sensor. The material on which the parabolic reflector is formed is tapered in thickness as a function of radius to eliminate phase delays introduced by the curvature as seen by the second RF seeker.

Laser beam scanning apparatus and method

Abstract: A laser beam scanning apparatus employs a movable reflector (32) having a large number of flat reflective sides (44) and a deflector (16) which shifts the laser beam (10) at high speed across a plurality of the reflective sides (44). The movement of the reflector (32) is synchronized with the deflection of the laser beam (10) to produce a desired scan pattern in a first scan direction (X). The reflective sides (44) of the movable reflector (32) may be angled relative to each other in a second direction (Y) to produce different scan lines thereby providing an X-Y scan pattern. The combined high speed beam deflection and motion of the reflector (32) provide scanning of the beam (10) in parallel scan segments thereby providing high scanning speed of the beam (10) with a high degree of resolution.

Mode Characteristics in Chirowaveguides with Constant Impedance Walls

Abstract: Modal propagation of electromagnetic waves in waveguides filled with chiral media, known as chirowaveguides, is studied. The waveguide walls are assumed to behave as constant impedance surfaces. This can model corrugated surfaces, dielectric coated metallic surfaces, as well as perfectly or imperfectly conducting walls. Conditions leading to modes with pure circular polarization are derived. Under these conditions, a chirowaveguide can act as a low crosspolar feed for reflector antennas.

Hyperfocal tracking solar thermal collector

Abstract: A solar thermal collector incorporates an extended reflector surface constructed to concentrate radiation from a radiation source along a focal line. The reflector surface is oriented in a generally upward facing direction relative to the earth with the focal line above the reflector surface. A tracking system supports the extended reflector surface for double axis tracking of the sun by relative motion of the reflector surface to different tracking positions for optimizing concentrated radiation at the focal line. The tracking system is constructed to maintain the focal line of the extended reflector surface in a substantially horizontal orientation relative to the earth during tracking. An elongate absorber is positioned substantially at the focal line for absorbing and converting radiation to heat energy. An elongate absorber housing is coupled to the extended reflector surface and is constructed for positioning the elongate absorber substantially along the focal line. The housing provides an insulating enclosure for the elongate absorber for reducing conduction heat loss. The housing is formed with an elongate aperture oriented in a generally downward direction relative to the earth for receiving and passing concentrated radiation from the extended reflector surface to the absorber. A leveling system is coupled to the absorber housing. The leveling system is constructed to maintain the absorber housing in a substantially horizontal attitude with the aperture facing downward relative to the earth during tracking to suppress convection heat loss from the absorber and absorber housing.

Radiant energy collecting apparatus.

Abstract: A radiant energy collecting apparatus (11) for collecting and concentrating solar energy having a primary parabolic reflector (16) which focuses the sun's rays on a focal line (18) and has a principle axis (17) passing through the focal line (18) and a secondary concentrating assembly (20) located adjacent the focal line (17) of the primary reflector (16). The secondary concentrating assembly (20) includes a pair of planar reflectors (26) arranged on opposite sides of the principle axis (17) of the primary reflector (16) and a series of secondary parabolic reflectors (28) between the planar reflectors (26), the secondary parabolic reflectors (28) having focal lines (29) which extend normal to the planar reflectors (26) and to the principle axis (17) of the primary reflector (16). The secondary reflectors (28) are mounted for rotation about their focal lines (29) and concentrate energy on targets (42) extending along their focal lines (29).

Curved reflector having a flexible substrate

Abstract: A planar reflector is composed of a base and a flexible substrate having a high reflection layer formed thereon and overlayed on the base with an adhesive layer interposed between the high reflection layer and the base. The adhesion strength between the base and the substrate is at least 100 g/cm, and the thickness of the adhesive layer is not smaller than 0.5 μm but not greater than 50 μm. A curved reflector can be obtained by bending the planar reflector so that a curved surface having a radius of curvature not greater than 5 mm is formed presenting a concave surface on a side of the flexible substrate.

Lighting fixture reflector containing ultraviolet absorber

Abstract: Reflective, metalized plastic films for use in lighting fixture reflectors have improved performance when the plastic film upon which the metalization layer is deposited contains ultraviolet absorber.

Recessed luminaire with a swivel housing

Abstract: A recessed luminaire having a first housing and a second housing The second housing has a light holder and a reflector disposed therein, the reflector having an edge portion defining an open end The first and second housings are connected by a joint, located at the edge portion of the reflector, which allows the second housing to swivel into and out of the first housing

Wide-angle passive infrared radiation detector

Abstract: An infrared radiation detector using a reflector comprising a mirrored conic section or faceted reflector to increase the field of view of a sensor. The reflector is mounted in the normal field of view of the sensor, and is truncated so as prevent the reflector from blocking radiation directly in front of the detector. The detector is mounted either on a wall with a nearly 180 degree field of view, or on a post with a nearly 360 degree horizontal field of view and a nearly 180 degree vertical field of view.

Reflector and a method of generating a reflector shape

Abstract: A reflector for radiation disseminated by a radiation source is of a shape with which the reflector curve of intersection in a plane including an axis (A) of the reflector and the radiation source comprises segments (S1-A1, A2-B2) of different conics whose merging is edge-free These conic segments are joined directly and the tangents at the point of contact (A1,A2) of two joined conic segments are alike A method of generating such a reflector is indicated as well

Annular slot patch excited array

Abstract: The target seeker system includes two radio frequency antennas consisting of two sets of radio frequency selective annular slot patch excited radiator receiver elements, one set for K-band energy, the other for X-band energy, sharing a common ground plane. The radio frequency antennas have a single multi-band image plate consisting of resonant dichroic surfaces which will selectively reflect X- and K-band energy. An image plate is formed with conductive patterns on each side of a low dielectric material. The reflective pattern acts as a quarter wavelength thick plate at the operating frequency. The top of the image plate which has X-band reflectors is spaced at one-half of the desired X-band wavelength above the ground plane and the K-band reflector on the bottom of the image plate is spaced at one-half of the desired K-band wavelength. The thickness of the image plate is adjusted to provide the appropriate relative spacing between the X-band reflecting surface on the top and the K-band reflecting surface on the bottom.

Simplified spacecraft antenna reflector for stowage in confined envelopes

Abstract: A method for stowing a unitary flexible antenna reflector 10 in a confining envelope and deploying the reflector from the envelope. In a most general sense, the invention includes the steps of: a) applying a deforming force to diametrically opposed positions 16 and 18 near an edge of the reflector 10 to place the reflector in a deformed state; b) maintaining the reflector 10 in the deformed state until deployment; and c) releasing the reflector 10 from the deformed state. In a specific embodiment, the step of maintaining the reflector 10 in a deformed state includes the step of attaching a restraining element between the diametrically opposed positions on the edge of the reflector which is released on deployment.