Reflector (antenna)

About: Reflector (antenna) is a research topic. Over the lifetime, 28730 publications have been published within this topic receiving 212618 citations.

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.

Semiconductor light emitting device, method for producing the same and reflector for semiconductor light emitting device

Abstract: A semiconductor light emitting device comprising a metallic supporting plate (1), an optical reflector (3) bonded to the supporting plate (1), a light emitting diode (2) bonded onto the supporting plate (1) in the inner cavity (3a) of the reflector (3), and a resin sealing body (6) sealing the outer circumferential part of the reflector (3) and the upper surface (1c) of the supporting plate (1). Since the reflector (3) is connected electrically with a wiring body (5) or the semiconductor light emitting diode (2) is connected with the wiring body (5) by means of fine lead wires (8) passing through a cut (3k) made between the light emitting diode (2) and the wiring body (5), the fine lead wires (8) connected with the semiconductor light emitting element can be protected against deformation by shortening the wiring distance of the fine lead wires (8), and optical directivity and front luminance of the semiconductor light emitting element can be enhanced by decreasing the diameter of the reflective surface (3c) of the reflector (3) and increasing the height from the supporting plate (1). Furthermore, thermal deterioration of resin can be avoided by forming the resin sealing body (6) of heat resistant resin because the inner cavity (3a) can be formed in the reflector (3).

Arecibo heating experiments

Abstract: Enhancements of various features of the incoherent scatter spectrum are observed when the ionosphere is illuminated with powerful, high frequency radio waves. The radio waves excite plasma instabilities producing lines or more complex spectral features near the local plasma frequency, at the local ion acoustic frequency, near the local gyrofrequency, and near twice the gyrofrequency. The enhancements occur in a thin slab as observed by the incoherent scatter radar and at both upshifted and downshifted frequencies with respect to the probing radar frequency. The enhancements are observed to vary with time when the excitation is held constant and is turned on or off. The high power radio waves are produced by a 160 kw transmitter feeding a log-periodic pair of curtains mounted at the focus of the 1000-ft reflector and covering the frequency range from 5 to 12 MHz. The effects are observed with the incoherent scatter radar using the same reflector and with ionosondes and photometers. The frequencies of the enhanced plasma line and the ion line and their relation to the pump (high frequency radio wave) frequency are predictable from available parametric instability theory. Other spectral features are being explained as the theory develops with the help of the observations. There remain some discrepancies, in particular the asymmetries in intensity, width, and fluctuations of the upshifted compared to the downshifted plasma lines.

Solar lighting reflector apparatus having slatted mirrors and improved tracker

Abstract: A solar lighting apparatus for illuminating the interior of a roofed building includes a reflector assembly rotatable about a vertical axis for tracking daily movements of the sun. The reflector assembly includes multiple planar reflector panels each extending about a horizontal axis and supported between a pair of opposing, parallel side frame members inclined upwardly toward their rear ends at approximately a 25° angle to the horizontal. The reflector panels are oriented in their operative position at right angles to the side frame members and are inclined at approximately a 65° angle to the horizontal. The reflector panels are spaced apart from one another by a distance approximating the width of each panel to prevent leading reflector panels from shading trailing reflector panels. Each of the reflector panels is secured to the side frame members about a pivotal connection for allowing the reflector panels to be rotated to a compact shipping position lying substantially within the plane defined by the side frame members. The reflector assembly is supported by a rotatable support ring geared to a drive motor selectively powered from a storage battery that is in turn charged by a first photovoltaic panel. A solar tracking circuit selectively couples the storage battery to the drive motor for rotating the reflector assembly. A second smaller photovoltaic panel directly powers the tracking circuitry to avoid draining the storage battery. The tracking circuitry prevents false tracking under cloudy-bright conditions, and automatically seeks the sun following extended hours of overcast conditions.

Electrically switchable polymer stabilised broadband infrared reflectors and their potential as smart windows for energy saving in buildings

Abstract: Electrically switchable broadband infrared reflectors that are relatively transparent in the visible region have been fabricated using polymer stabilised cholesteric liquid crystals. The IR reflectors can change their reflection/transmission properties by applying a voltage in response to changes in environmental conditions. Simulations predict that a significant amount of energy can be saved on heating, cooling and lighting of buildings in places such as Madrid by using this switchable IR reflector. We have also fabricated a switchable IR reflector which can also generate electricity. These polymer based switchable IR reflectors are of high potential as windows of automobiles and buildings to control interior temperatures and save energy.