Showing papers on "Reflector (antenna) published in 1999"

Directive photonic-bandgap antennas

Abstract: This paper introduces two new photonic bandgap (PBG) material applications for antennas, in which a photonic parabolic reflector is studied. It is composed of dielectric parabolic layers associated to obtain a PBG material. The frequency gap is used to reflect and focus the electromagnetic waves. This device has been designed using a finite-difference time-domain (FDTD) code. FDTD computations have provided the theoretical reflector's directivity. These results are in good agreement with measurements, and it appears that the PBG reflector presents the same directivity as a metallic parabola. A second application uses a defect PBG material mode associated with a metallic plate to increase the directivity of a patch antenna. We explain the design of such a device and propose experimental results to validate the theoretical analysis.

Radio frequency identification transponder having a high gain antenna configuration

Abstract: A radio frequency identification transponder has a high gain antenna for increased range. In an embodiment, the radio frequency transponder has a reflector to increase its operative range. A system of one or more reflectors is operatively associated with a transponder and may be formed out of any sort of radio frequency reflective material. The reflector system can enhance reception or transmission of radio waves by or from the transponder. The reflector system may also be used to provide for selective coupling of the radio frequency transponder with a base station, user- or vehicle-supported reader, or the like based on relative orientation. In addition, the reflector system may be used to selectively reflect particular radio waves. In another embodiment, the radio frequency transponder has a horn antenna providing increased gain and directivity. In yet another embodiment, the radio frequency transponder has a patch antenna providing increased gain and circular polarization. The patch antenna may further comprise a patch antenna array, a multi-layer patch or a dipole comprised of patch elements.

Method and apparatus for measuring substrate temperatures

Abstract: An apparatus for measuring the temperature of a substrate in a thermal processing chamber. The substrate is suspended above a reflector to form a reflecting cavity. A probe of a temperature sensor has an input end positioned to receive radiation from the reflecting cavity and an output end optically coupled to a detector to provide a temperature reading. The temperature sensor is configured to reduce the effect that radiation which has an axis of propagation within an angle of an axis normal to the reflector, e.g., substantially normal radiation from a portion of the substrate adjacent to the input end of the probe, has on the temperature reading.

Multiple frequency reflector antenna with multiple feeds

Abstract: A reflector antenna system with multiple feeds each operating in a separate frequency band. The antenna system includes a main parabolic reflector and an ellipsoidal subreflector configured in a Gregorian arrangement. Mutual blockage between the multiple feeds is reduced by their orientation and arrangement. The system includes a transversely positioned feed and an axial feed located in the focal region of the main reflector. The transverse feed may be integral with the subreflector. The system also includes a third feed placed at the virtual focal point of the subreflector.

SiO2/TiO2 omnidirectional reflector and microcavity resonator via the sol-gel method

Abstract: Thin films of SiO2 and TiO2 were used to fabricate one-dimensional photonic crystal devices using the sol-gel method: an omnidirectional reflector and microcavity resonator. The reflector consisted of six SiO2/TiO2 bilayers, designed with a stopband in the near infrared. Reflectivity over an incident angle range of 0°–80° showed an omnidirectional band of 70 nm, which agrees with theoretical predictions for this materials system. The microcavity resonator consisted of a TiO2 Fabry–Perot cavity sandwiched between two SiO2/TiO2 mirrors of three bilayers each. We have fabricated a microcavity with resonance at λ=1500 nm and achieved a quality factor of Q=35. We measured a resonance frequency modulation with a change in incident angle of light and defect layer thickness.

Apparatus and method for providing spherical viewing during endoscopic procedures

Abstract: The present invention is an improved apparatus and method for providing variable-angle endoscopic views in a cavity, such as an internal cavity in a human patient. The apparatus includes an elongated tubular portion with a viewer at its proximal end and a reflector assembly at its distal end. The reflector assembly includes a first reflector and a second reflector, with the second reflector rotationally mounted to permit its rotation about an axis generally aligned with an optical path portion passing from the first reflector to the second reflector. The viewer is preferably a camera rotatably secured to the apparatus. A rotator controls rotation of the second reflector and the camera, so that rotation of the second reflector causes a corresponding rotation of the camera. The assembly thus permits near-spherical viewing of the cavity without requiring substantial movement of the endoscope.

Modeling of an electrohydraulic lithotripter with the KZK equation.

Abstract: The acoustic pressure field of an electrohydraulic extracorporeal shock wave lithotripter is modeled with a nonlinear parabolic wave equation (the KZK equation). The model accounts for diffraction, nonlinearity, and thermoviscous absorption. A numerical algorithm for solving the KZK equation in the time domain is used to model sound propagation from the mouth of the ellipsoidal reflector of the lithotripter. Propagation within the reflector is modeled with geometrical acoustics. It is shown that nonlinear distortion within the ellipsoidal reflector can play an important role for certain parameters. Calculated waveforms are compared with waveforms measured in a clinical lithotripter and good agreement is found. It is shown that the spatial location of the maximum negative pressure occurs pre-focally which suggests that the strongest cavitation activity will also be in front of the focus. Propagation of shock waves from a lithotripter with a pressure release reflector is considered and because of nonlinear propagation the focal waveform is not the inverse of the rigid reflector. Results from propagation through tissue are presented; waveforms are similar to those predicted in water except that the higher absorption in the tissue decreases the peak amplitude and lengthens the rise time of the shock.

Directional reflector shield assembly for a microwave ablation instrument

Abstract: A directional reflective shield assembly (25) is provided for a microwave ablation instrument (20) having an antenna (23) coupled to a transmission line (21). The antenna (23) is formed to generate an electric field sufficiently strong to cause tissue ablation. The shield assembly (25) includes a cradle device (26) disposed about the antenna (23) in a manner substantially shielding a surrounding area of the antenna (23) from the electric field radially generated therefrom. The cradle device (26) further provides a window portion (27) communicating with the antenna (23) which is strategically located relative the antenna to direct a majority of the field generally in a predetermined direction.

Semiconductor device with reflector

Abstract: A semiconductor device includes a substrate, a semiconductor chip for emitting light, and a reflector enclosing the semiconductor chip for reflecting the light emitted from the semiconductor chip. The substrate is provided with a first electrode and a second electrode each electrically connected with the semiconductor chip. A transverse cross-section of the reflector defines an elongated figure, such as oblong, elliptical, rhombic or rectangular.

Design and analysis of multiple-beam reflector antennas

Abstract: Simplified design and analysis equations are presented for multiple-beam reflector antennas based on the Gaussian-beam analysis of the primary and secondary patterns. The derived equations are useful for the quick design and performance analysis in terms of the coverage-area directivity and the inter-beam isolation of multiple-beam antenna systems. Results of the analysis given in this paper agree well with rigorous computations based on physical-optics analysis of the reflector-antenna radiation patterns. Extension of the analysis to multiple-beam lens antennas, and to shaped/contoured-beam antennas, is also presented.

Optical identification element

Abstract: An optical component in the form of an identification element (such as for counterfeit protection or copy protection) includes an optically anisotropic layer comprising regions of different optical axes that is arranged over a reflector The anisotropic layer may be implemented with a liquid crystal polymer in which the orientation of the liquid crystals is different in different areas Such an orientation pattern is initially hidden from a viewer, but becomes visible by means of an additional polariser To improve the visual appearance of the identification element, a white light hologram may be used for the reflector

Reflection type liquid crystal display device

Abstract: A reflector electrode is provided with hills and valleys thereon, and the reflector electrode is formed on an inside face of a transparent substrate having a transparent electrode and an opposite substrate. Light-scattering-liquid-crystal is provided with forward-scattering component and back-scattering component, so that scattering of reflected light from the reflector electrode is increased when the light-scattering-liquid-crystal is transparent. As a result, contrast is less dependent on a viewing angle, and a brighter quality display with higher color purity can be obtained.

Infrared radiation sources, sensors and source combinations, and methods of manufacture

Abstract: A blackbody radiation device ( 110 ) includes a planar filament emission element ( 102 ) and a planar detector ( 104 ) for respectively producing and detecting radiation having width dl/l less than about 0.1 to test a sample gas, where l is the wavelength of the radiation; a reflector ( 108 ); a window (W); an electrical control ( 118 ); and a data output element ( 116 ).

System and method of radio transmission between a radio transmitter and radio receiver

Abstract: An antenna assembly providing selectable omnidirectional or directional reception of radio transmissions in a frequency band in accordance with the invention includes an electrically conductive reflector ( 432 ) defining a cavity ( 702 ) having a bottom ( 708 ), an opening ( 714 ) and a surface ( 704 and 706 ) extending from the bottom to the opening and an electrical output ( 763 ); an electrically conductive loop ( 431 ) coupled to ground and having an electrical outlet ( 766 ) for coupling to an RF amplifier ( 407 ), the loop being positioned between the bottom opening of the cavity; a RF switch ( 406 ) having an input ( 760 ) and first and second outputs ( 762 and 764 ), the RF switch having a first switching state electrically connecting the input to the first output and a second switching state electrically connecting the input to the second output, the first switch output being electrically coupled to ground and the second switch output being electrically coupled to the output of the electrically conductive loop; and wherein the first switching state provides the directional reception and the second switching state provides the omnidirectional reception of the radio transmissions.

Shock wave-inertial microbubble interaction: methodology, physical characterization, and bioeffect study.

Abstract: A method of generating in situ shock wave–inertial microbubble interaction by a modified electrohydraulic shock wave lithotripter is proposed and tested in vitro. An annular brass ellipsoidal reflector (thickness=28 mm) that can be mounted on the aperture rim of a Dornier XL-1 lithotripter was designed and fabricated. This ring reflector shares the same foci with the XL-1 reflector, but is 15 mm short in major axis. Thus, a small portion of the spherical shock wave, generated by a spark discharge at the first focus (F1) of the reflector, is reflected and diffracted by the ring reflector, producing a weak shock wave approximately 8.5 μs in front of the lithotripter pulse. Based on the configuration of the ring reflector (different combinations of six identical segments), the peak negative pressure of the preceding weak shock wave at the second focus (F2) can be adjusted from −0.96 to −1.91 MPa, at an output voltage of 25 kV. The preceding shock wave induces inertial microbubbles, most of which expand to a maximum size of 100–200 μm, with a few expanding up to 400 μm before being collapsed in situ by the ensuing lithotripter pulse. Physical characterizations utilizing polyvinylidene difluoride (PVDF) membrane hydrophone, high-speed shadowgraph imaging, and passive cavitation detection have shown strong secondary shock wave emission immediately following the propagating lithotripter shock front, and microjet formation along the wave propagation direction. Using the modified reflector, injury to mouse lymphoid cells is significantly increased at high exposure (up to 50% with shock number >100). With optimal pulse combination, the maximum efficiency of shock wave-induced membrane permeabilization can be enhanced substantially (up to 91%), achieved at a low exposure of 50 shocks. These results suggest that shock wave–inertial microbubble interaction may be used selectively to either enhance the efficiency of shock wave-mediated macromolecule delivery at low exposure or tissue destruction at high exposure.

Efficiency enhancement of a coaxial virtual cathode oscillator

Abstract: The microwave field intensity around the virtual cathode oscillator was enhanced by using a microwave reflector in the output waveguide. The experimental results show that the microwave output power strongly depends on the position and geometry of the microwave reflector. The maximum microwave efficiency obtained was twice as large as that without field enhancement by the microwave reflector.

Method and apparatus for mode locking of external cavity semiconductor lasers with saturable Bragg reflectors

Abstract: External cavity semiconductor lasers using a saturable Bragg reflector as an external reflector are mode locked and produce output pulses of 1.9 ps from a semiconductor lasers without dispersion compensation. By coupling the output to a standard single mode fiber with a length of 35 m to compensate the linear chirp, the mode-locked pulse duration as short as 880 fs is achieved.

External cavity type wavelength-tunable light source

Abstract: An external cavity type wavelength-tunable light source including an optical amplifier on one end surface of which an antireflection film is coated, a diffraction grating arranged on an emission light axis of the optical amplifier on the side of the antireflection film and having wavelength selectivity, a reflector arranged on a reflection light axis of the diffraction grating, for reflecting a reflection light beam from the diffraction grating, and a wavelength tuning mechanism for tuning a wavelength of an lasing light beam by changing an angle of the reflector relative to the reflection light axis of the diffraction grating. The wavelength tuning mechanism includes a bimorph type piezo-electric element as a wavelength-tunable controlling unit for changing an angle of the reflector relative to the reflection light axis of the diffraction grating, and a wavelength-tunable driving circuit for controlling a voltage applied to the bimorph type piezo- electric element to tune the wavelength of the lasing light beam.

Broadband fixed-radius slot antenna arrangement

Abstract: A fixed radius tapered slot antenna ( 100 ) formed a dielectric substrate ( 10 ) with an electrically conductive layer ( 14 ) on one side. The slot is defined by two hemispherical shaped elements ( 12, 13 ). A common base ( 15 ) is also formed on the conductive layer behind the hemispherical shaped members. Preferably, a microstrip feedline ( 16 ) is formed on the side of the dielectric substrate to electromagnetically couple to the balun (18) adjacent the narrow end of the tapered slot. A contiguous array of fixed radius tapered slot antennas ( 100 ) can he made on the same conductive layer of a dielectric layer. A reflector can he integrated with the antenna array to improve the radiation pattern. The fixed radius tapered slot antenna has been proven to out-perform an exponentially tapered slot or Vivaldi antenna.

Radio frequency identification transponder having a reflector

Abstract: An improved radio frequency transponder has a reflector to increase its operative range. A system of one or more reflectors is operatively associated with a transponder and may be formed out of any sort of radio frequency reflective material. The reflector system can enhance reception or transmission of radio waves by or from the transponder. The reflector system may also be used to provide for selective coupling of the radio frequency transponder with a base station, user- or vehicle-supported reader, or the like based on relative orientation. In addition, the reflector system may be used to selectively reflect particular radio waves.

Dual band antenna

Abstract: A flat-plate dual band array antenna is described which comprises two flat plate arrays of single band antenna elements, each of which operates in a different frequency band. The two flat plate arrays are positioned one above the other, with areas in the upper flat plate array being removed in order that the antenna elements in the lower flat plate array can radiate through the upper flat plate array. The geometric arrangement of the antenna elements is such that distribution networks for the antenna elements can be accommodated in the limited space available. Dual band flat-plate array feeds for a reflector antenna are also described. These use at least two flat-plate arrays that are positioned one above the other. Again regions in the upper flat-plate array are removed to allow the lower flat-plate to operate through the upper one. The geometric arrangement of the antenna elements in these array feeds is such that transmit and receive beams are provided that have co-incident phase centers and approximately equal beamwidths. The flat plate array antenna and reflector antennas described are particularly useful for subscriber satellite communication systems such as satellite TV, with receive signals being in the Ku band and transmit signals being in the Ka band.

System and method for aligning aircraft coordinate systems

Abstract: A system and method for aligning aircraft coordinate systems includes determining a first coordinate in the first coordinate system from a first reflector using a first coordinate positioning device, and determining second and third coordinates in the second coordinate system from second and third reflectors, respectively, using a second coordinate positioning device. The second and third reflectors are disposed at predetermined distances from the first reflector. The system aligns the first and second coordinate systems based on the first, second, and third coordinates and the predetermined distances using a processor.

Wavelength tunable narrow linewidth resonant cavity light detectors

Abstract: A light detector comprising a photodetector disposed within an etalon or microcavity. The light detector is sensitive to light having a wavelength resonant with the etalon. Preferably, the etalon is a solid state microcavity having distributed bragg reflectors. The photodetector may be a photodiode, phototransistor or the like. The etalon has a front reflector with reflectivity R f and a back reflector with reflectivity R b . The photodetector has a double-pass absorption of A. In the present invention, R f , R b , and A are selected such that R f =R b (1−A). The combination of the back reflector and absorbing photodetector is indistinguishable from a single reflector of reflectivity R f . Therefore, the light detector behaves like an etalon with matched reflectors. Preferably, R f is greater than 0.95 and R b is greater than 0.98. The photodetector can have a relatively thin absorption layer, thereby providing high speed capability. Even with a low absorption, the photodetector provides high quantum efficiency since it is within the etalon. Preferably, the front reflector is movable such that an etalon cavity length is adjustable. This provides for adjustment of the wavelength at which the light detector is sensitive.

Numerical optimization of a cylindrical reflector-in-radome antenna system

Abstract: Accurate numerical optimization based on rigorous solution of the integral equation using the method of analytical regularization is performed for a cylindrical reflector antenna in a dielectric radome. It is shown that the multiple scattering in this system is more significant for the optimum radome design than any nonplane-wave effects or the curvature of the radome. We claim that, although the common half-wavelength design is a good approximation to avoid negative effects of the radome (such as the loss of the antenna directivity), one can, by carefully playing with the radome thickness, its radius, reflector location, and the position of the feed, improve the reflector-in-radome antenna performance (e.g., increase the directivity) with respect to the same reflector in free-space.

Solar cell array with multiple rows of cells and collapsible reflectors

Abstract: An improved solar panel for a spacecraft. The solar panel has a rigid base, at least one row of solar cells, and at least one elongated, collapsible, self-deploying reflector. Preferably, a plurality of rows and the reflectors are mounted on the face of the base and are generally parallel to each other in an alternating fashion. The deployed reflector forms a triangular shape having a first and second reflecting side that reflects radiation onto adjacent rows of solar cells. The collapsible reflector has a reflector sheet and an erector that deploys the sheet to form the triangular shape. The sheet is mounted to the base along its two lengthwise edges. The erector is mounted to the base beneath the sheet and adjacent to one of the sheet's lengthwise edges. The erector has a rigid erector arm that tilts upwardly to engage the underside of the sheet and to deploy the sheet into the triangular shape. The deployed triangular shape comprises a first and second reflecting side that reflects incident radiation onto adjacent rows of solar cells. Preferably, the first and second reflecting sides of the reflector are substantially symmetrically disposed about the longitudinal bisecting plane of the reflector when the reflector is in a deployed position.

High power multiwavelength light source

Abstract: In accordance with the invention, a multiwavelength light source comprises a length of optical waveguide amplifier, a multiwavelength reflector for reflecting a plurality of different spectrally separated wavelengths optically coupled to one side of the amplifier and a low reflection output coupled to the other side. A broadband source is provided for passing broadband light to the multiwavelength reflector. In the preferred embodiment, the reflector is a plurality of reflective Bragg gratings, the waveguide amplifier is a length of rare-earth doped fiber (e.g. EDF) and the broadband source is the amplifier pumped to generate ASE. In operation, broadband light is transmitted to the gratings. Light of wavelength channels corresponding to the reflection wavelengths of the gratings is reflected back through the amplifier for further amplification before it arrives at the output. Optionally one or more transmission filters can be disposed between the reflector and the amplifier (or at the output) ASE source to control the relative magnitudes of the selected channels.

Gyrotron internal mode converter reflector shaping from measured field intensity

Abstract: We present the formulation and experimental results of a new approach to designing internal mode converter reflectors for high-power gyrotrons. The method employs a numerical phase retrieval algorithm that reconstructs the field in the mode converter from intensity measurements, thus accounting for the true field structure in shaping the beam-forming reflectors. An outline for designing a four-reflector mode converter is presented and generalized to the case of an offset-fed shaped reflector antenna. The requisite phase retrieval and reflector shaping algorithms are also developed without reference to specific mode converter geometry. The design approach is applied to a 110 GHz internal mode converter that transforms the TE/sub 22,6/ gyrotron cavity mode into a Gaussian beam at the gyrotron window. Cold test experiment results of the mode converter show that a Gaussian beam with the desired amplitude and phase is formed at the window aperture. Subsequent high-power tests in a 1 MW gyrotron confirm the Gaussian beam observed in cold tests. The general development of the approach and its validation in a quasi-optical mode converter indicate that it is also applicable to other quasi-optical, microwave applications such as radio astronomy, free-space transmission lines, and mitre bends for overmoded waveguides.

Laser chamber with minimized acoustic and shock wave disturbances

Abstract: A laser chamber (100) had angled reflectors (116, 118) that reflect acoustic and shock waves away from the laser discharge area (103) to minimize acoustic and shock wave disturbances. The angled reflector may have different configurations to assist in the dissipation of the acoustic and shock waves. For example, the angled reflector (116, 118) may have a modulated reflective surface, such as having grooves or holes defined within the surface. Further, the angled reflector (116, 118) may have a reflective surface with acoustic and shock wave absorbing properties. The reflective surface with absorbent properties may be a felt metal or have multiple layered porous surfaces. In addition, the walls of the laser chamber (100) may be modulated to assist in the dissipation of the acoustic waves and shock waves through absorption, scattering, and by generating interference within the reflected waves. Multiple layered porous surfaces may be used along the walls to absorb and scatter incident waves. The walls of the laser chamber (100) may also be covered with an acoustic and shock wave absorbing material, such as felt metal. In other embodiments, the walls of the laser chamber (100) are modulated with grooves (132), such as triangular or rectangular horizontal grooves, which scatter incident waves and generate interference within reflected waves.

Optical functional element and transmission device

Abstract: A distributed feedback laser comprising: waveguide (4) having a hologram (10) capable of emitting radiation mode light in upper and lower directions; first reflector (20) provided below said waveguide for returning said radiation mode light back to said waveguide; and second reflector (21A, 21B, 21C, 21D, 21E) provided above said waveguide for returning said radiation mode light back to said waveguide, intensity profile of said radiation mode light on said waveguide being non-uniform is disclosed. Also, by using 2nd- or higher-order diffraction gratings having an asymmetric cross-sectional configuration together with a reflection structure located at one side thereof, a highly directional optical isolator can be provided. Further, the present invention provides an optical functional element comprising: first waveguide which guides optical waves and has a gain or a loss, said waveguide having a hologram (202) capable of coupling with said optical waves guided by said waveguide to generate radiation mode light; amplifier (203) for amplifying said radiation mode light released from said first waveguide and releasing it; and first reflector (204) for reflecting said radiation mode light emitted from said amplifier back to said first waveguide.

Dual band antenna

Abstract: A dual band antenna with dual antenna elements, each including a first and a second antenna element (5b, 6b), for transmitting and/or receiving radio frequency radiation in a first, relatively low frequency band and a second, relatively high frequency band, respectively, and an electrically conductive, substantially planar reflector device (1) Each first antenna element (5b) is located close to an associated one (6b) of the second antenna elements on a front side of the reflector device so as to define first and second radiation beams The reflector device, on each lateral side thereof, is provided with an edge portion formed as a groove (11, 12), which is open towards the front side of the reflector device and which is dimensioned so as to widen the azimuth beam width of the second beam to an angular value being close to that of the first beam, whereby both beams will have substantially the same azimuth width