Showing papers on "Reflector (antenna) published in 1976"

Microwave holographic metrology of large reflector antennas

Abstract: A microwave holographic technique for the determination of amplitude and phase of the principal and cross-polarized aperture fields of large reflector antennas is described. The hologram formation process utilizes the elevation over azimuth scanning system normally associated with these antennas, and, in this respect, appears to be unique among other proposed methods of field probing. The present work describes the means used to obtain vital information on the antenna structure such as E - and H -plane phase centers of the feed, and rms values of the reflector surface profile errors. Accurate prediction of E - and H -plane radiation patterns in the near- and far-field is also demonstrated.

Solar concentrators with maximal concentration for cylindrical absorbers.

Abstract: The differential equation is derived that describes the reflector of an ideal two-dimensional radiation concentrator with an absorber of arbitrary convex shape. For the special case of an absorber with circular cross section, the equation can be solved in closed form if suitable coordinates are used. The effect of absorption at the reflector is considered, and formulas are presented for determining the attenuation of radiation on its passage from aperture to absorber.

Digital wavemeter of cw lasers

Abstract: The ratio of an unknown laser wavelength to that of a standard is quickly determined by a two-beam interferometer with a corner-cube reflector moving on an air track. Standard and unknown wavelength beams travel identical paths in opposite directions, so refractive index corrections are minimized. Accuracy is about six parts in 10/sup 8/. Absolute measurements of some iodine hyperfine component wavelengths are reported.

Semiconductor body heater

Abstract: A semiconductor body heater is provided with a planar array of radiant heating elements spaced from a reflector. In the preferred embodiment, each radiant heating element comprises a tungsten filament quartz lamp. Each lamp is removable and replaceable without disengaging any other lamp. The reflector is cooled by flows of gas and liquid coolant therethrough. Flows of gas between the planar array of lamps and the reflector and between the reflector and a cover member also cool the apparatus. Various diffusers for substantially eliminating temperature nonuniformities over an area illumined by the planar array of lamps are also disclosed. The semiconductor body heater of the present invention is particularly well suited for use in a temperature gradient zone melting process.

Some highlights in reflector antenna development

Abstract: Reflector antennas have been used since the radio pioneering era of Lodge, Hertz, and Marconi, but it took the exigent demands of radar in World War II to stimulate a real development in the reflector art. Subsequent interest in the science of radio astronomy and the inception of microwave ground communication links were responsible for a burgeoning growth in the field, so that in the 1940s and 1950s the design principles and requirements for prime focus fed systems were well established. Cassegrain, or secondary focus systems, and horn reflectors came into prominence in the early 1960s with the advent of satellite tracking and communication networks. The desire to maximize the gain, or the gain-temperature ratio, then led to development of sophisticated techniques for properly shaping the illumination over the reflector aperture in order to maximize efficiency and minimize spillover, among them being the shaping of the sub-reflector in Cassegrain systems and the use of multimode and hybrid mode feed horns. Not all reflector antennas utilize paraboloidal surfaces. Some recent developments in line source feeds make the spherical reflector attractive for scanning applications and the conical reflector for deployable, space-borne antennas. The large 1000-foot diameter reflector at Arecibo is a well known example of the former. Although some extremely large spaceborne reflector antennas have been proposed and studied, the largest now in use appears to be the unfurlable 30-foot reflector carried by ATS-6. Finally, some gain comparisons are given for a few of the (electrically) largest reflectors that have been built both for radio astronomy and for space communications. If some milestones in reflector development have been overlooked it is due to the limitations inherent in a review paper.

Solar energy collector apparatus

Abstract: The present invention includes a solar energy collector for concentrating the sun's rays on a conduit having a fluid flowing therethrough. A primary reflector is oriented in a north-south direction. The sun's rays are reflected from the primary reflector to a smaller secondary reflector located thereabove, which further reflects the sun's rays onto a conduit recessed below the primary reflector. The concentrated sun's rays on the conduit heats the conduit. The heated conduit further heats a fluid flowing through the conduit. The heated fluid is used to generate energy, directly or indirectly. An automatic control device, including a light sensor, continually adjusts the primary and secondary reflectors to insure that the sun's rays are striking the primary reflector at the proper angle. Adjustments of the primary and secondary reflectors are made by pivotal movement about the conduit which does not move.

Servo tracking apparatus

Abstract: The servo tracker of the instant invention comprises an apparatus for positioning of a major reflector to compensate for relative movement between the Earth and Sun. A base member supports a movable major reflector and a fixedly positioned minor reflector. The major reflector is movable in both a north/south and east/west direction. When correctly positioned, the major reflector directs the light rays of the Sun toward a major target where useful energy is produced. When correctly positioned, a portion of the reflected light rays from the major reflector are reflected by the minor reflector toward a minor target positioned adjacent a pair of sensors. When the major reflector is improperly positioned due to relative movement between the Sun and Earth, the reflected light rays from the minor reflector are directed toward one of the sensors depending at which axis the major reflector is improperly positioned and the direction required for repositioning to a correct position. When receiving the Sun's light rays, the sensor heats causing expansible fluid within a closed hydraulic system to expand causing a linear actuator connected between the base and one of the axis of the major reflector to actuate and reposition the major reflector until the Sun's rays from the minor reflector are again directed toward the minor target. Both of the axes of movement of the major reflector have a sensor and actuator system. The major reflector is designed to return from a Sun set position by gravity to a position for reflecting the morning light rays of the Sun toward the major target.

Liquid crystal display device for colored display of information with a selective polarizer

Abstract: A liquid crystal display device for the colored display of information with a reflector and a twisted nematic liquid crystal cell placed between a linear and a selective polarizer is disclosed. The selective polarizer is disposed in front of the twisted nematic liquid crystal cell and the linear polarizer is disposed between the twisted nematic liquid crystal cell and the reflector.

Reflector with light-scattering surface for liquid-crystal displays and method for their manufacture

Abstract: A novel light scattering reflector and methods of making and using it are disclosed. The reflector, which can advantageously be used in conjunction with liquid crystal displays, includes a layer carrier formed of glass or rigid PVC foil. The layer carrier is roughened by sandblasting, impressing with a grooved die, or by other techniques to provide an irregular surface. A reflective metal coating is subsequently evaporated onto the roughened surface to complete the reflector structure. Auxiliary materials may also be coated onto the layer carrier to improve the characteristics of the device.

Solar energy reflector-collector

Abstract: A system including a non-tracking reflector-collector for the concentration and collection of solar energy. An energy-collecting plate is disposed upright along a substantially horizontal axis substantially coincident with the east-west direction of the earth. The collector plate is positioned within a semi-tubular reflector having parabolic sidewalls. The reflector surfaces on opposite sides of the collector plate are parabolic surfaces, each having a focal point approximately coincident with the upper terminal edge of the collector plate. The axes of the parabolas which define the respective surfaces are rotated about or diverge from their common focal point at a substantial angle. The reflector sides are of laminated construction having a base portion of a lightweight rigid plastic sheet, an underlayer of plastic corrugated board and a reflective film on the interior surface. The collector plate receives energy entering the aperture between the reflective surfaces. In one of the preferred embodiments, the plate elevates the temperature of a heat exchange medium flowing therethrough. The heat exchange medium provides for storage and use of the collected energy. In a second embodiment, the collector plate receives solar energy which is converted into electrical energy for storage and use.

Cycloramic image projection system

Abstract: A cycloramic image projection system in which an image as viewed from a central point, is projected in a complete circle about the viewer's position onto a drum-type screen. Included is a conical reflector arranged concentrically with the optical axis of a circular beam of light projected onto the reflector and which is turned in a radially outward direction and condensed through the picture area of a circular loop of film on a sprocket also concentric with the optical axis and which surrounds the reflector. A toroidal convex lens surrounds the film loop concentrically and serves to focus and project a 360° image of the picture onto the screen, and the film loop is continuously wrapped on and off around the reflector whereby a continuously changing but temporarily stationary 360° image is swept onto and off the screen. The sprocket and reflector are stationary, the toroidal lens is mounted on a pan table which rotates about the optical axis, and an arm on the table serves to pull the film from one reel, feed it through a slit in the lens, thence around the sprocket and back through the slit where it is rewound on the other reel.

Antenna for combined surveillance and foliage penetration radar

Abstract: An L-band radar and antenna array operating with an existing X-band surveance radar to provide a foliage penetration capability. The foliage penetration antenna consists of an array of L-band, stripline dipole/director elements placed in front of an array of broadwall waveguide slots which define an X-band aperture. The X-band aperture in addition to its own function, serves as a reflector for the dipole/director elements. Aperture sharing is thus provided for a dual frequency antenna without increasing the size of the existing X-band aperture.

Analysis of the radiation patterns of reflector antennas

Abstract: The development and application of a numerical technique for the rapid calculation of the far-field radiation patterns of a reflector antenna from either a measured or computed feed pattern are reported. The reflector is defined by the intersection of a cone with any surface of revolution or an offset sector of any surface of revolution. The feed is assumed to be linearly polarized and can have an arbitrary location. Both the copolarized and the cross polarized reflector radiation patterns are computed. Calculations using the technique compare closely with measured radiation patterns of a waveguide-fed offset parabolic reflector. The unique features of this technique are the freedom from restrictive feed assumptions and the numerical methods used in preparing the aperture plane electric field data for integration.

Refractor-reflector radiation concentrator

Abstract: A small-area focus solar concentrator comprising a linear echelon refractor and a linear echelon reflector. The increments of the refractor are crossed at approximately 90° to the increments of the reflector. The refractor and reflector cooperate to focus solar radiation incident on the front surface of the refractor to a small area focus in front of the refractor. The refractor-reflector structure permits relatively low cost, high power concentrators using refractor-reflector matrices. Also, the refractor-reflector structure can be used to focus normal or non-normal incident radiation outside the path of the radiation to reduce or eliminate blockage of the radiation by an absorber located at the focus.

The design of correcting secondary reflectors

Abstract: A computer program called DERIVE is described for the design of the reflecting surfaces of two-mirror radio telescopes. It calculates the shape of a secondary reflector to any given primary by use of geometrical optics, yielding zero path length errors for all paraxial rays. The only condition to be fulfilled is (for Cassegrain types) that incoming rays, after reflection at the primary, do not cross each other before reaching the secondary. Equations for this condition are given. This method can be used to improve existing telescopes at short wavelengths by correcting for the surface deviations of the primary reflector with a specially shaped secondary. The results of 17 calculated examples are described, for various types of deviations

Optical scanning system with canted and tilted reflectors

Abstract: A target scanning system for radiation seeking guided missiles. Radiation incident on a Cassegrainian reflector system images at a focal point on a primary optic axis. The Cassegrainian reflector system produces a first scanning pattern and diverts it to a tertiary reflector. The tertiary reflector has its reflective face canted from its spin axis to produce a second scanning pattern. The two scanning patterns combine to produce the desired rosette scan that is scanned over a sensor.

Passive and active pulse stacking scheme for pulse shaping

Abstract: Apparatus and method for producing a sequence of radiation pulses with a pulse envelope of time variation which is controllable by an external electromagnetic signal applied to an active medium or by a sectored reflector, through which the radiation passes

Low cost linear/circularly polarized antenna

Abstract: A linear/circularly polarized antenna system is provided by four conductive elements. The conductive elements are joined in pairs at their ends with the joined ends spaced by a conductive support member from a flat reflector. The lengths of the conductive elements of each dipole element are changed from being equal lengths of approximately a quarter operating frequency wavelength to one slightly longer and the other slightly less than a quarter wavelength to selectively change operation from that of a linearly polarized antenna to that of a circularly polarized antenna.

Controlled flexible membrane reflector

Abstract: The embodiments of the disclosed controlled flexible membrane reflector show a system wherein the optical surface of a reflector is electrostatically controlled. By controlling the electric field acting on selected portions of the flexible membrane which bears the optical surface, the shape of the optical surface can by dynamically controlled. A figure sensor or image quality detector detects deviations of the reflecting surface of the membrane from the desired figure and a feedback control system adjusts selected portions of the electric field to return the reflective surface to its proper figure. The differential control of the electric field is accomplished by segmenting a back electrode and controlling the voltage on each segment individually. The control voltage varies around a nominal value applied to all segments which is required to deflect the surface into its desired shape.

Indicating temperature within living tissue

Abstract: A reflector that reflects a microwave signal as a function of temperature is implanted within living tissue of a human. A microwave signal is transmitted to the reflector via an applicator in contact with the skin of the human. A portion of the signal reflected from the reflector is coupled via the applicator to a meter that provides an indication of the temperature of the reflector.

Acoustic surface wave resonator with suppressed direct coupled response

Abstract: Acoustic surface wave resonator device having two sets of reflector arrays on a piezoelectric substrate with structurally modified coupling transducers interposed therebetween, wherein the transducers are coupled to the standing wave resonance in the resonance cavity but are respectively decoupled from the surface wave launched by the other transducer, thereby suppressing direct coupled response without materially affecting the resonance response. In a typical embodiment, a pair of interdigital transducers are disposed between two sets of reflector arrays on a piezoelectric substrate, with the fingers of the respective transducers including intermediate off-set portions thereof. Specifically, the intermediate off-set portion in each interdigital finger extends over a distance λ/4, with the space between successive fingers in a transducer being λ/2. The reflector arrays are spaced to set up a standing wave at resonance, and the transducers are so located to dispose the center line of each finger on the peak of the standing wave. The off-set portions in the fingers of the respective transducers extend in opposite directions so as to cause the wavefront of a wave launched by one transducer to have a 180° phase shift along the length of the finger of the other transducer. The net change in the finger due to this wave is zero such that no signal is generated, thus suppressing the transducer response.

L-band radar antenna array

Abstract: A stripline horizontally polarized dipole and passive director antenna ar, operative at L-band (1220-1280MHz), mounted in a 90° corner reflector constructed of a grid of cylindrical rods which are hinged along its apex permitting folding of the reflector over the antenna array to protect the elements of the array, for example, during transport.

Ground plane corner reflectors for navigation and remote indication

Abstract: A device to be used as a guidance system for sonar or radar or similar transmissions in which a dihedral reflector is used in association with part of the earth's surface (land or sea) whereby a trihedral reflector results for such transmissions in which spurious signals are avoided because the earth forms one of the reflective surfaces to thereby remove spurious signals which could otherwise occur with a normal trihedral reflector.

Solar energy system

Abstract: A system for collecting solar energy consists of a target for absorbing solar radiation positioned above a plurality of independently positionable reflectors, each reflector including a base, a concave circular reflecting surface, and means responsive to incident solar radiation for positioning the reflector with respect to the target and the sun such that solar radiation incident upon the reflectors will be directed toward the target. The system can also include means for initiating the positioning of the reflectors only in response to the presence of the sun above a predetermined minimum angle with respect to the horizon.

Luminous effects device

Abstract: A luminous effects device including a partially silvered mirror, a frusto-conical reflector having a plurality of lights disposed about its inner periphery and a spherical reflector, all of which are disposed within a closed container and aligned in series so that multiple reflections occur between the partially silvered mirror, frusto-conical reflector and spherical reflector to create an endless tunnel effect that can be viewed through the opposite side of the partially silvered mirror.

Optical system for lasers

Abstract: A laser configuration is disclosed wherein the active region is of annular cylindrical form. Zero mode azimuth coupling which produces an output beam of low obscuration ratio in the near field, thereby providing a single lobe in the far field, is achieved by the use of an unstable optical resonator characterized by an annular mirror defining one end of the resonator and a two stage axiconic reflector disposed optically between the opposite ends of the resonator.

Wide angle scanning antenna assembly

Abstract: An antenna assembly wherein the direction of a beam of radio frequency energy may be changed by combining the effects of a mechanically movable reflector and an electromagnetic lens is disclosed. In the preferred embodiment the antenna arrangement includes a corporate monopulse feed arranged to produce a linearly polarized divergent beam which is first reflected from a linearly polarized paraboloid to direct a convergent beam toward a mechanically rotatable polarization-twisting reflector. A selected portion of a spherical electromagnetic lens arrangement is illuminated by the still convergent beam from the latter reflector, such lens then determining the direction of the beam finally propagated in free space. The relative positions of the corporate monopulse feed, the linearly polarized paraboloid, the mechanically rotatable polarization-twisting reflector and the characteristics of the spherical electromagnetic lens arrangement are selected so that, for a given antenna assembly for electromagnetic energy of a given frequency, the linearly polarized divergent beam from the corporate monopulse feed is converted to a substantially collimated beam in free space.

Bulb-type solar energy collector

Abstract: There is disclosed a molded glass bulb-type solar collector which includes a parabolic specular reflector member and integral glass tubular member closed at the inner end extends along the focal axis of the reflecting surface. A shank portion of the tubular member extends outside the parabolic reflector and is open at the outer end. The tubular wall has its outside surface within the reflector coated with a wave length selective coating. A transparent glass cover plate that is preferably convex (domed) is sealed over the large open end of the reflector at a peripheral flange. The flange is formed to a regular geometric configuration, viz, square, diamond, hexagon, etc., and several of the bulb collectors are fabricated into a curtain wall with these flanges in adjacent relationship. The space within the cover plate and reflector is pumped to a vacuum. The shank portion of the member is connected into an aperture of a manifold. The collectors are connected in series wherein working fluid is carried in a conduit, and at each aperture, a partition extends into the tubular member bisecting it so that the fluid on one side of the partition is diverted in a counterflow path therethrough and back to the conduit on the other side of the partition. In another form of manifold, collectors are connected in parallel, so to speak, wherein two parallel divided passages are provided in the manifold.

Solar water heater of natural circulation type

Abstract: A solar water heater of natural circulation type provided with a reflector for improving the heat collecting efficiency of a heat collector especially in the winter season The reflector is disposed to satisfy two essential conditions The first essential condition provides that solar radiation reflected from the reflecting surface of the reflector be substantially entirely directed toward the heat collecting surface of the heat collector at the southing time of the winter solstice, while the second essential condition provides that solar radiation incident upon the heat collecting surface of the heat collector be not excessively interrupted by the reflector at the southing time of the summer solstice