Showing papers on "Reflector (antenna) published in 1970"

Analysis of reflector antennas

Abstract: Monograph on analysis of reflector antennas covering electromagnetic field equations, computer aided design, etc

Support for antenna device

Abstract: A support comprising a triangular frame pivotally mounted on a tower for supporting an antenna or reflector and means for locking said frame in an adjusted position.

Variable Metal Mesh Coupler for Far Infrared Lasers

Abstract: In a far infrared molecular laser the traditional pierced output mirror has been replaced by an infrared interference filter, consisting of two metal mesh reflector grids. By adjusting the spacing between the two parallel grids, the reflectance of the filter can be varied. Theory and experiment of this variable reflector are presented. It allows convenient optimization of the coupling conditions of a laser for maximum power output. In contrast to hole coupling, the interference filter provides uniform coupling over the entire cross section of the reflector. This reduces the diffraction losses and improves the angular distribution of the output beam. The variable reflector has also been used to determine the linear gain of the laser.

Light reflector system

Abstract: A multi-sided light reflector for a light source, which reflector incorporates curved reflector surfaces that cooperate with a light source disposed within the reflector to permit only primary reflections from the light source to be emitted from a reflector opening. The reflector includes a plurality of curved side reflecting surfaces disposed in angular relationship with a plurality of curved corner reflector surfaces disposed between the side reflector surfaces and joined to the side reflecting surfaces. The line of juncture between the side reflector surfaces and the corner reflector surfaces is curved and the lower point of each of the corner reflector surfaces is defined by intersection of the curved lines of juncture of the respective corner reflectors and is disposed in the plane of the reflector opening. The reflector opening, from which direct and primary reflections are emitted, is defined by the primary exit pupil ray of the light source from the various side and corner reflectors.

Head-up display apparatus

Abstract: A head-up display apparatus for a craft comprises means for projecting a display of information and a partially transparent reflector associated with the display projection means. The reflector has either an operative position in which the projected display is reflected by the reflector to appear in an observer''s line of sight through the reflector or a retracted position out of the observer''s line of sight. The apparatus also includes means for displacing the reflector from the operative position to the retracted position, and means sensitive to radiant energy, the reflector displacement means being controlled in accordance with the radiant energy sensed by the radiation-sensitive means to effect the displacement of the reflector in response to change in radiation sensed by the radiation-sensitive means.

Electronically controllable primary feed for profile-error compensation of large parabolic reflectors

Abstract: The paper shows that it is possible to compensate for the effects of mechanical profile errors in large parabolic reflectors, by means of a specially designed multielement feed array situated in the focal plane of the reflector. The factors relating the magnitude and period of these profile errors to the size and complexity of the compensating feed are discussed, and a novel method is described for achieving this compensation by controlling the phasing of the array. The system employs a spatial Fourier-transforming device, and its use is mainly restricted to long-period profile errors. Experimental results of this process, derived from a small-scale laboratory system employing a 1-dimensional 5ft parabolic reflector incorporating an 8-element feed, are presented. These results demonstrate compensation for profile errors up to π/2 radians. The possible application of this technique to existing and new reflectors is discussed.

Vehicle control system and equipment

Abstract: A vehicle warning and control system and equipment is disclosed utilizing radio frequencies and the Doppler principle wherein one of the vehicle lights acts as the R.F. radiator, reflector, receiving antenna as well as an illuminator, and through standard circuitry supplies a warning signal or a brake activating signal.

Multi-purpose antenna employing dish reflector with plural coaxial horn feeds

Abstract: A microwave antenna useful on a spacecraft, which utilizes a single dish reflector and single coaxial horn structure to transmit at two frequencies, and to receive signals at a third frequency that allow tracking. The horn structure includes a coaxial wave-guide with an inner pipe for transmitting X-band waves, an intermediate pipe, surrounding the inner pipe for transmitting S-band waves through the space between it and the inner pipe, and an outer pipe surrounding the intermediate pipe for receiving S-band tracking signals. An outer horn flares from the outer pipe and an inner horn flares from the inner pipe, to efficiently illuminate the dish reflector at both X and S bands.

The analysis of deployable umbrella parabolic reflectors

Abstract: The radiation characteristics of an umbrella-type reflector are studied in detail. When the supporting ribs of the quasiparabolic reflector are parabolic in shape and the surface between any two adjacent ribs is the surface of a parabolic cylinder, the deviation of the surface from the true parabolic shape has the effect of spreading the focal point of the parabolic reflector into a focal region, the limits of which can be calculated from the knowledge of the reflector parameters. The best feed position can be accurately determined by requiring that the phase error over the surface be minimized. For the cosine to the power n illumination, numerical results showing the gain degradation, the shift in optimum focal point, and the change in secondary patterns, due to the deviation of the reflector surface from the true parabolic surface, are presented.

Millimeter wave antenna system

Abstract: A millimeter wave antenna mounted on a satellite includes a parabolic reflector fabricated of carbon fiber reinforced plastic (CFRP) composite material to enable the parabolic shape of the reflector to be maintained to within three percent of a millimeter wave length despite possible temperature variations on the order of 300 DEG F. between portions of the reflector illuminated by the sun and in the umbra. Waveguides, fabricated from CFRP, for a feed positioned approximately at the focal point of the reflector are the sole mechanical supporting means for the feed. To take advantage of the physical properties of the carbon fiber reinforced plastic composite materials a honeycomb structure is sandwiched between layers of the CFRP. The surface of the reflector illuminated by the feed is coated with a thin film of aluminum which functions as a millimeter wave reflector. The waveguide CFRP interior is coated with a thin film of aluminum to provide the millimeter wave conducting surface.

Luminaire reflector comprising elliptical and parabolic segments

Abstract: Substantially uniform magnitude of illumination on a plane surface is provided by a concave reflector having a parabolic reflecting surface and an elliptical reflecting surface oriented relative to one another to satisfy the following criteria.

The wide angle side lobes of reflector antennas

Abstract: : The complete pattern of a parabolic reflector antenna was calculated using the singly-diffracted rays of the geometrical theory of diffraction, with proper corrections for the forward and real axial directions. Excellent agreement with experimental patterns can be expected, if the aperture blockage is not significant. The solution has the usual advantages of a solution based on the geometrical theroy of diffraction, namely, it is obtained in the form of simple functions, its computation cost is low, it is directly related to the radiation mechanism of the antenna and so it can be readily used in the design problem, and it can be easily extended and modified as the need arises.

Electronic distance measuring method and apparatus

Abstract: An electronic distance measuring device and method for determining the distance between two locations utilizing electromagnetic or light wave energy. The wave energy is transmitted from one location to the other and is reflected back toward the transmitting location. The reflected energy is detected and compared in phase with the transmitted energy, and the phase relationship between the transmitted and detected energy varied until a predetermined phase relationship exists. The predetermined phase relationship is selected so that the wave energy along the path between the transmitter, reflector and detector contains an integral number of wavelengths of wave energy. A time gate related to the propagation of the wave energy along this path is generated and distance is displayed digitally in response to the time gate and a highly stable reference frequency signal.

Compensation of spherical reflector aberrations by planar array feeds

Abstract: The feasibility of correcting phase aberrations of spherical reflector antennas with planar array feeds has been investigated. This type of feed seems to be particularly attractive for applications requiring several closely spaced beams. A synthesis procedure for the array excitation has been developed which minimizes the mean-square error with respect to a prescribed reflector illumination. This method was applied to the analysis of a spherical reflector antenna with a 642\lambda diameter and an effective F number of 0.9.

Optimum design of a Gregorian-corrected spherical-reflector antenna

Abstract: An investigation into the performance of spherical-reflector antennas with Gregorian correctors is described with particular reference to their application in satellite-communications ground stations. Feeds comprising corrugated scalar horns propagatinga balanced HE11 hybrid mode are considered, this choice eliminates cross-polarisation components of field in the spherical-reflector aperture. The theoretical performance of the spherical reflector with various subreflector profiles is estimated by using the aperture-field method to calculate the antenna-gain factor, far-field radiation pattern and overall efficiency as functions of the subreflector and feed positions. An optimum subreflector profile is chosen on the basis of maximum overall efficiency for a particular feed and antenna-scan angle. It is concluded that, for conventional scalar horns, the side-lobe level of the far-field radiation pattern is rather high, being about −11.5 dB with a corresponding gain factor of 0.85 and an overall efficiency of 0.65 for a scan angle of ±7°. Much lower side-lobe levels can be achieved, together with high gain factors, but only with lower overall efficiency. The spherical-reflector-antenna performance is compared to that of a front-fed paraboloid with the same feed and a higher efficiency is predicted for the former antenna. Preliminary consideration is given to the design of a dualmode feed so as to provide an additional tracking pattern, also to initial mechanical-design aspects.

High resolution millimeter reflector antennas

Abstract: The foremost millimeter reflector antennas in use are surveyed. Antenna descriptions are written by personnel at the institutions operating the antennas. The antennas described are the following: 1) MIT 28-foot and 120-foot (U.S.A.), 2) Lebedev and Crimean RT 22-meter (USSR), 3) Aerospace 15-foot (U.S.A.), 4) University of Texas 16-foot (U.S.A.), 5) AFCRL 29-foot (U.S.A.), 6) Bonn University 10-meter (Germany), 7) (CRC (DRTE) 30-foot (Canada), 8) NRAO 36-foot (U.S.A.), 9) Berkeley 20-foot (U.S.A.), and 10) JPL 18-4oot (U.S.A.). Antenna system descriptions include information on antenna performance, pointing capabilities, limitations, and principal applications. The antennas are used in radio astronomy and communication research. The reference section covers the major results obtained with the antennas.

A high-performance line source feed for the AIO spherical reflector

Abstract: An aberration-correcting line source feed has been designed, modeled, constructed, and tested in the Arecibo reflector. The feed is a linearly polarized flat wavegnide 40-foot-long array illuminating 700 feet of the 1000-foot-diameter spherical reflector at 318 MHz. The antenna, illuminated by the new feed, yields an aperture efficiency of 70 percent with a peak gain near 56 dB, half-power beamwidth of 16.2 minutes of arc, and sidelobe levels below 4 percent of the on-axis gain. Vignetting losses are approximately 30 percent at the highest zenith angle.

Rapid deployment corner reflector

Abstract: A readily deployable, lightweight radar reflector having a large radar signature, the invention is compactly stowable aboard a carrier vehicle, immediately assuming an erect configuration on ejection from an airborne or surface vehicle. The present reflector is particularly intended to be ejected from aircraft traveling at high speeds, the erection of the reflecting surface being provided by the internal bias of pre-stressed hoops surrounding and supporting the reflecting surface.

Device for particularly continuous checking and/or indication of curvatures arising in gun barrels

Abstract: A device for sensing for a curvature in a gun barrel, comprising a reflector fixedly mounted near the muzzle of the gun and a source of light and detector means fixedly mounted near the rear portion of the gun barrel, is provided

Design of flared-horn primary feeds for parabolic reflector antennas

Abstract: The paper describes the derivation of a simple design procedure by which the dimensions of a rectangular flared-horn primary feed, operating in the TE10 mode, may be determined for parabolic reflectors, having any f/d ratio and with either a rectangular or circular contour, so that maximum aperture efficiency is obtained. The design technique is based on achieving a best match between the principal component of the reflector focal-plane electric field and that electric field existing in the horn mouth during transmission. In addition, the design procedure predicts the value of the spillover power, the reradiated power, the relative edge-field illumination, the resultant reflector aperture-field distribution and the value of the maximum aperture efficiency obtainable for the given combination of horn feed and reflector.

Mechanically swept radar antenna for use with an aircraft landing monitor system

Abstract: An radar antenna for use in an aircraft landing monitor which includes an elongated antenna housing mounted on a vertical pivot for horizontal oscillation in the nose of an aircraft. An elongated horn reflector mounted along the housing supports a resonant edge-slotted waveguide array therein for transmitting and receiving radar signals with a radar beam pattern narrower in the azimuth than in the elevation plane. An elongated bar spring is mounted in the housing and is rigidly attached to the vertical pivot in order to tend to maintain the desired oscillation of the antenna housing. A motor oscillates the antenna housing about the vertical pivot to sweep the radar beam over a predetermined azimuth angle. Circuitry is provided to sense the position of the antenna housing and for maintaining the antenna sweep at the predetermined azimuth angle and rate.

Heat absorbing reflector utilizing a metallic substrate

Abstract: A reflector, for reflecting generally all wavelengths of radiation of visible light from a multilayer interference reflecting coating for generally concentrated projection of the visible light and for absorbing substantially all wavelengths of radiation of heat, is provided for by a metallic substrate having formed thereon, between it and the multilayer interference reflecting coating, an antireflection coating having a continuously graded refractive index for transmission therethrough of wavelengths of heat radiation for absorption into the metallic substrate.

Radiation Characteristics of Bent-Wire Antennas

Abstract: A mathematical model, which predicts the far-field power pattern of a wire antenna bent in one plane, is developed, and the classical approximation of a sinusoidal current distribution along the arc length is employed, neglecting all end and mutual coupling effects. General expressions for the complex Poynting vector, electric- and magnetic-field intensities are also derived in terms of the retarded vector potential. Although the theory for parabolically-bent antennas compares favorably with experiment, it is shown that the agreement is more favorable when the current distribution is computed by the method of moments. In contrast to the figure-eight ?-plane pattern of the conventional straight dipole, the circularly and parabolically bent antennas operating at the first resonance are shown to have radiation patterns approaching omnidirection as the bending curvature is optimized, thus lending themselves to use as replacements for many common dipole applications for gain standards, field probing, reflector feeds, as well as mobile and broadcast antennas.

Independent aircraft landing monitor system

Abstract: An aircraft landing monitor which is independent of ground-based guidance systems and which includes an antenna comprising an elongated housing pivotally mounted about a vertical axis for horizontal movement in the forward portion of an aircraft. The housing supports an edge-slotted waveguide array which is mounted in an elongated horn reflector to thereby direct an antenna radiation pattern forward of the aircraft which is narrower in the azimuth than in the elevation plane. A motor oscillates the antenna housing about the vertical axis to sweep over an azimuth angle sufficient for airport runway detection during a glideslope approach to the runway by the aircraft. Radar transmitter and receiver circuits transmit and receive pulse radar signals via the antenna for radar detection of the runway. A radarscope mounted in the cockpit control panel is responsive to the radar transmitter and receiver for visually displaying an approaching airport runway in real-world linear perspective.

Adjustably positionable reflectors

Abstract: A reflector assembly in accordance with the present disclosure comprises a deformable reflector mounted within a housing by an adjustablemounting means. The adjusting mounting means is capable of selectively adjusting the configuration and position of the reflector in the housing. Preferably, at least one region of the reflector is fixedly positioned with the housing and other regions of the reflector are independently selectively positioned in the housing to thereby selectively alter the configuration of the reflector.

Backfire antennas with dipole elements

Abstract: A method is set up for a theoretical investigation of arbitrary backfire antennas based upon dipole structures. The mutual impedance between the dipole elements of the antenna is taken into account, and the field radiated due to a surface wave reflector of finite extent is determined by calculating the surface current distribution on the reflector plate. Numerical results obtained for Yagi backfire antennas and short-backfire antennas using this theory are compared with experimental results.

Apparatus for and method of obtaining precision dimensional measurements

Abstract: A plurality of beams of electromagnetic energy having different known wavelengths in a vacuum are each operatively associated with an interferometer having a movable reflector to provide an output fringe pattern for each beam characterized by alternating annulment and reenforcement fringes. The reflector is moved causing movement of the fringes of each beam past an associated detector which provides an electrical output signal in response to alternating ones of the fringes as they move therepast whereby the electrical output signals represent a count of alternate fringes of each beam. The electrical output signals from the detectors are scaled and summed to provide a combination signal which represents the actual distance moved by the reflector and such distance has been inherently corrected for variations in ambient conditions.

Current-rated short-arc lamp for light projection apparatus

Abstract: A direct-current short-arc xenon lamp is mounted in prefocused relationship with either a parabolic or an ellipsoidal reflector so that the optical axis of the reflector is aligned with the longitudinal axis of the lamp. The spacing between the lamp electrodes is smaller than that used heretofore and the focal point of the reflector is located at a predetermined position along the arc path. The lamp is rated and operated at a predetermined current within a range of from 70 to 200 amperes and the electrodes are spaced from 4.6 to 7.0 millimeters apart, depending upon the particular operating-current rating of the lamp. When the lamp is operated in a horizontal position, a magnet located adjacent the lamp and outside of the reflector is used to prevent upward bowing of the arc. In the case of a movie projection system, the shorter and more intense arc increases the screen lumens and decreases the power (watts) consumed by the lamp.

Apparatus for indicating the direction to a sound pulse source

Abstract: Apparatus including a reflector constituting a part of a spherical, cylindrical or other concave reflecting surface and a thin film detector of concentric or flat planar shape located in the focusing zone of the reflector between the center of curvature and the reflecting surface. The detector is provided with means, such as a high cracking lacquer coating which will be fractured in the focal zone of the sound pulse, to provide a line-of-sight locating point which, in a three-element device, is combined with the center of curvature of the reflector to give the line-of-sight direction to the source of the sound pulse, the focal point for any sound source falling on a line drawn through the center of curvature of the reflector to that source. Instead of the center of curvature, means indicating a line or plane therethrough may be used with the lacquer fracture point to determine the direction to the sound source. In a two-element device the detector may comprise a photographic film on which there appears an inverted image of the field of view whereby the location of the fracture point on the image indicates the direction to the sound source, in which case the center of curvature and the line or plane therethrough are unnecessary.