Showing papers on "Parabolic reflector published in 2014"

Enclosure for radio, parabolic dish antenna, and side lobe shields

Abstract: Enclosures for radios, parabolic dish antennas, and side lobe shields are provided herein. A dish antenna includes a parabolic circular reflector bounded by a side lobe shield that extends along a longitudinal axis of the dish antenna in a forward direction forming a front cavity, and a sidewall that extends along the longitudinal axis of the dish antenna in a rearward direction forming a rear cavity.

Interval Arithmetic for Pattern Tolerance Analysis of Parabolic Reflectors

Abstract: An innovative analytic strategy for the estimation of the average pattern behavior of reflector antennas when surface deformations are present on the parabolic disc is proposed. Since measuring the surface deviations from a reference ideal shape is a complex task, the root-mean-square (rms) surface deformations are modeled as intervals and their impact on the power pattern as well as the sensitivity of the beam features is efficiently predicted by exploiting the rules of the interval arithmetic throughout interval analysis (IA). The result is the definition of closed-form relationships between the bounds (upper and lower values) of the radiated power pattern and the rms interval surface deformations. Uniformly and non-uniformly distributed perturbations of the ideal surface are analyzed to assess the effectiveness of proposed approach. Comparisons with state-of-the-art solutions are also carried out by varying the deformation thickness as well as the reflector geometry and illumination.

Long-wave infrared digital holographic interferometry with diffuser or point source illuminations for measuring deformations of aspheric mirrors

Abstract: Long-wave infrared digital holographic interferometry with CO2 laser and microbolometer arrays has been developed for testing the large deformations of space reflectors. The setup considered is a Mach–Zehnder, associated to the digital holography reconstruction of the wavefront in the inline configuration with phase shifting. Two possibilities exist for illuminating the tested reflector: either with a point source (similarly to classical interferometry) or an extended source (with a diffuser). This paper presents the development of a modular setup which allows comparing both in the case of a parabolic mirror.

Fast and Accurate Analysis of Reflector Antennas With Phased Array Feeds Including Multiple Reflections Between Feed and Reflector

Abstract: Several electrically large phased array feed (PAF) reflector systems are modeled to examine the mechanism of multiple reflections between parabolic reflectors and low-and high-scattering feeds giving rise to frequency-dependent patterns and impedance ripples. The PAF current is expanded in physics-based macro domain basis functions (CBFs), while the reflector employs the physical optics (POs) equivalent current. The reflector-feed coupling is systematically accounted for through a multiscattering Jacobi approach. An FFT expands the reflector radiated field in only a few plane waves, and the reflector PO current is computed rapidly through a near-field interpolation technique. The FEKO software is used for several cross validations, and the convergence properties of the hybrid method are studied for several representative examples showing excellent numerical performance. The measured and simulated results for a 121-element Vivaldi PAF, which is installed on the Westerbork Synthesis Radio Telescope, are in very good agreement.

Realizing a Flat UWB 2-D Reflector Designed Using Transformation Optics

Abstract: This paper presents the design and experimental validation of a flat ultra-wideband 2-D reflector designed using transformation optics (TO). The flat TO reflector mimics the electromagnetic characteristics of a curved parabolic reflector that is rotated about its apex to reflect the incident wave to a prescribed direction. The TO reflector is true-time-delay (TTD) in nature and it offers a very large bandwidth which is theoretically unconstrained. The proof-of-concept TO reflector design is explored by employing an effective material with an inhomogeneous electric response which is realized by an array of dipoles. We experimentally verify the principle of operation of the reflector over a 67% bandwidth and show that it maintains good radiation characteristics and low beam squint. The design considerations, benefits and drawbacks of the proposed TO reflector are discussed.

A Practical Approach to Locate Offset Reflector Focal Point and Antenna Misalignment Using Vectorial Representation of Far-Field Radiation Patterns

Abstract: A direct and unambiguous approach to determine the focal point of a single offset reflector is presented. The proposed approach makes use of the vectorial form of far-field radiation patterns, both amplitude and phase. The method is based on iteratively defocusing the primary feed laterally and axially. First, mathematical expressions of the offset reflector with a small lateral and axial defocused feed are reviewed. Then, the numerical results are presented. It is shown how the corresponding far-field phase pattern information can be utilized to optimally locate the focal point of an offset parabolic reflector. The method can also be used to place the phase center of an unknown feed on the reflector focal point, and align the reflector on a test tower.

Metal-only Fresnel zone plate antenna for millimetre-wave frequency bands

Abstract: A metal-only Fresnel zone plate antenna (FZPA) to operate at millimetre wave frequency bands is presented in this work. The proposed antenna is a very attractive alternative to parabolic reflectors and reflectarrays because of its several advantages such as low profile, low cost, easy to manufacture and lossless. A centre-fed Fresnel zone plate whose diameter is 300 mm has been designed and analysed at 75 GHz providing a gain of 44.29 dBi, an aperture efficiency of 48.42% and a cross-polarised level lower than −40 dB for the diagonal plane (ϕ = 45°). A second prototype has been designed and analysed from 54 to 68 GHz to evaluate the performance of the proposed antenna compared with an already published FZPA.

Modeling and Analysis of a Solar Parabolic Dish Thermoelectric Generator

Abstract: This article presents the modeling and analysis of a thermoelectric power generator driven by a solar parabolic dish collector. The system is modeled by a set of steady state energy balance equations from the first law of thermodynamics for two main components of the solar parabolic dish collector and thermoelectric power generator. The developed model is analyzed for various operating conditions and design parameters. Modeling results are compared with experimental results and they are within 10% accuracy.

Energy Distribution Along the Focal Axis of a Metallic Cylindrical Parabolic Reflector Covered With a Plasma Layer

Abstract: The deviation of the energy distribution along the focal axis of a long metallic cylindrical parabolic reflector, which on its surface contains a uniform cold collisionless plasma, is investigated. In addition, the effects of some physical parameters such as the plasma and wave frequencies and the thickness of plasma layer on this energy distribution and the reflected and the transmitted electromagnetic fields are studied. It is shown that the maximum value of the reflected intensity increases by increasing the incident wave frequency and by decreasing the plasma layer thickness and the plasma frequency.

The design of a parabolic reflector system with high tracking tolerance for high solar concentration

Abstract: A compact high concentrating photovoltaic (HCPV) module based on cassegrain optics is proposed; consisting of a primary parabolic reflector, secondary reflector and homogeniser. The effect of parabolic curvatures, reflector separation distance and the homogeniser’s height and width on the tracking tolerance has been investigated for optimisation. In this type of HCPV, the addition of a solid transparent homogeniser to the two stage reflector design greatly improves the tracking tolerance. Optical simulation studies show high optical efficiencies of 84.82 – 81.89 % over a range of ±1 degree tracking error and 55.49% at a tracking error of ±1.5 degrees.

Experimental Analysis of Parabolic Solar Dish with Copper Helical coil Receiver

Abstract: Solar Parabolic Dish is currently used for the Water heating and cooking applications. Generally Solar Parabolic Dishes are fixed focus point concentrators, but in order to achieve higher thermal efficiency we tried to make it line focus concentrator by using a unique receiver (copper tube in the form of helical coil) mounted at focal point.This report presents experimental platform based on the design, development and performance characteristics of direct steam generation by non-tracking solar paraboloidal dish concentrating system. The performance of the concentrator is experimentally investigated with the water circulated as heat transfer fluid. The system is fabricated with highly reflective aluminium foil sheet (0.8 reflectance factor). The experimental setup is placed in open, and the tests were carried out. The collector's efficiency was noted. The results are encouraging to provide the data for developing steam generation for rural application. The concentrated heat is absorbed by a copper tube which is made up of coil in a curved shape (22cm diameter and length with 15 no of turns) and it is fixed on solar trace path in which, it is eliminates tracking the sun in the east west direction and optimal tracking of the sun in the north-south to obtain maximum solar energy. The experimental results are taken on summer and cloud free days. The test results were measured 215 o C with solar steam conversion efficiency is 60-70%

Broadband TeraHertz wave time domain detection and light spot imaging integrated device and adjustment method

Abstract: The invention relates to a broadband TeraHertz wave time domain detection and light spot imaging integrated device and an adjustment method. According to the method, a TeraHertz wave time domain detection system and a light spot imaging system are combined together, a turnable concave lens, a turnable reflector and an off-axis parabolic mirror provided with through holes in a drilled mode are installed on a movable platform and used for adjusting and switching the systems, in the actual operation process, only the position of the turnable concave lens and turning of the turnable reflector need to be adjusted according to actual experiment situations, adjustment of the broadband TeraHertz wave time domain detection device and the light spot imaging device can be achieved, and therefore quick switch between the TeraHertz wave time domain detection device and the light spot imaging device can be achieved. The broadband TeraHertz wave time domain detection and light spot imaging integrated device is simple in structure, easy to operate and suitable for TeraHertz waves generated through different principles and TeraHertz waves with different spectrum widths.

Inverse problem for shape control of flexible space reflectors using distributed solar pressure

Abstract: This paper investigates controlled elastic deflection of thin circular space reflectors using an inverse problem approach to non-linear thin membrane theory. When changing the surface reflectivity across the membrane, the distributed loads due to ambient solar radiation pressure can be manipulated optically, thus controlling the surface shape without using mechanical or piezo-electric systems. The surface reflectivity can in principle be modulated using uniformly distributed thin-film electro-chromic coatings. We present an analytic solution to the inverse problem of finding the necessary reflectivity distribution that creates a specific membrane deflection, for example that of a parabolic reflector. Importantly, the reflectivity distribution across the surface is found to be independent of membrane size, thickness and solar distance, enabling engineering of the reflectivity distribution directly during the manufacture of the membrane.

Experimental Analysis of 2.7 m 2 Scheffler Reflector and Formulation of a Model

Abstract: The performance of 2.7 m 2 Scheffler reflector has been studied. Scheffler Reflector is parabolic dish collector designed to collect energy from sunlight. In this System storage vessel was installed at focus point . Vessel stores 10 ltr of water for the purpose of experimentation. Tests were carried out with this set up for the purpose experimentation. Performance analysis of the reflector revealed that average power and efficiency in terms of water boiling tests to be 550 W and 19%. Maximum temperature of water was observed to be 94 0 C. Ambient temperature was observed to be in between 32 o C and 40 0 C.

Freeform Lens Design to Achieve 1000X Solar Concentration with a Parabolic Trough Reflector

Abstract: Line-focus parabolic trough mirrors for solar thermal generation cannot produce the high concentration required for concentrating photovoltaic (CPV) systems. We describe a freeform lens array with toroidal symmetry which intercepts the low-concentration line focus to produce a series of elongated, high-concentration foci. The design employs 2D Kӧhler illumination to improve the acceptance angle in one direction. The two-stage concentrator has 1000X average geometric concentration with an acceptance angle of +/-1.49° in the azimuthal direction and +/-0.29° in the elevation direction. Preliminary results of a prototype roll-forming process are shown in thermoplastics and B270 glass.

Method for detecting large-caliber large-relative-aperture parabolic reflector surface shape error

Abstract: The invention relates to a method for detecting a large-caliber large-relative-aperture parabolic reflector surface shape error. An existing method is high in cost and low in accuracy and efficiency. The method includes the steps of selecting a transmission standard lens, adjusting the position of a laser wave surface interferometer, adjusting a focus of a tested parabolic reflector to be coincided with a focus of the laser wave surface interferometer, adjusting the optical axis of the tested parabolic reflector to enable the optical axis of the tested parabolic reflector and the optical axis of the laser wave surface interferometer to be coaxial, adjusting a standard plane reflector, rotating the laser wave surface interferometer to enable the laser wave surface interferometer to be aligned with a first annular sub-aperture A, and repeating the sixth step and the seventh step according to a sub-aperture division scheme. The method for detecting the large-caliber large-relative-aperture parabolic reflector surface shape error is low in cost and high in accuracy and efficiency.

Near-infrared spectrometer and measuring method thereof

Abstract: The invention discloses a near-infrared spectrometer. The near-infrared spectrometer comprises a light source, a parabolic mirror, a blazed grating, a digital micromirror device, a linear detector, a single-photon detector and a spectral information processing system; the light source is arranged on the focus of the parabolic mirror, the light source is collimated through the parabolic mirror and then projected to the blazed grating, light is divided into monochromatic parallel light on a first-level blazing angle through the blazed grating, and the monochromatic parallel light is projected to the digital micromirror device; a micromirror in the digital micromirror device deflects by +12 degrees and -12 degrees to respectively reflect the monochromatic parallel light on the linear detector and the single-photon detector; fusion processing is performed on spectral information received by the two detectors through the spectral information processing system to obtain spectral intensity of an original spectral signal. The invention further discloses a measuring method of the near-infrared spectrometer. The single-photon detector is introduced into the near-infrared spectrometer, so that the ability to detect trace substances and weak spectra is improved, sensitivity and precision are improved, and the structure is simple.

Non-tracking low-power concentrating solar thermal collector

Abstract: The utility model discloses a non-tracking low-power concentrating solar thermal collector which comprises a framework, a CPC compound parabolic reflector group, a plurality of evacuated collector tubes and an ultra-white high-transmitting toughened glass cover plate. The frame comprises a backboard and a frame fixed to the outer edge of the backboard, and an installation space is defined by the backboard and the frame. The CPC compound parabolic reflector group is made of high-reflection mirror aluminum through coating stamping forming of an interface curved surface, the CPC compound parabolic reflector group comprises a plurality of CPC compound parabolic reflectors which are distributed in parallel, the back surfaces of the CPC compound parabolic reflectors are shaped through polyurethane foam materials or polystyrene foam materials, and the CPC compound parabolic reflectors are stably installed in the installation space. The inner inter-layers of the evacuated collector tubes are respectively in a vacuum state, a heat conduction tube is installed in each evacuated collector tube, and the heat conduction tubes in every two adjacent evacuated collector tubes are communicated with each other. The upper end of the installation space in the framework is covered with the ultra-white high-transmitting toughened glass cover plate, so that the installation space is closed. The non-tracking low-power concentrating solar thermal collector is simple in structure, can effectively prevent external damage, and is long in service life, good in heat collection effect and convenient to assemble and transport.

Medium-and-small-diameter high-luminous-intensity LED annular-irradiation signal lamp

Abstract: The utility model discloses a medium-and-small-diameter high-luminous-intensity LED annular-irradiation signal lamp which comprises a multi-surface cylindrical heat dissipation body, an annular parabolic reflector component arranged on the periphery of the multi-surface cylindrical heat dissipation body, and an annular convex lens arranged in the annular space defined by the reflection surface of the annular parabolic reflector component, wherein an LED luminous unit is fixed to each outer plane of the multi-surface cylindrical heat dissipation body, the annular parabolic reflector component is formed by multiple straight-strip-shaped parabolic reflector units, light scattered by each LED luminous unit is reflected by the reflection surface of the corresponding straight-strip-shaped parabolic reflector unit, and light scattered by the LED luminous units and light reflected by the annular parabolic reflector component are converged in the vertical direction and then diffused in the horizontal direction in an annular mode by the annular convex lens. The medium-and-small-diameter high-luminous-intensity LED annular-irradiation signal lamp solves the problem that there is still part of light not effectively utilized for existing annular-irradiation lamps, and the light utilization rate is higher than that of the existing annular-irradiation lamps under the condition of the same power.

DOAS measurement system by means of polarizing beam splitting

Abstract: The invention discloses a DOAS measurement system by means of polarizing beam splitting. The DOAS measurement system comprises a lambda/4 wave wafer, a polarizing beam splitting piece, a parabolic mirror primary mirror, a corner mirror, an optical fiber, a power source device and a spectrograph detector. By means of the characteristics of the polarizing beam splitting piece, due to the fact that a signal carrying an absorbing spectrum passes through the lambda/4 wave wafer for two times, the polarizing state will change, and the signal will be reflected to the receiving optical fiber by the polarizing beam splitting piece; due to the fact that a telescope stray light signal which does not carry the absorbing spectrum and is not in atmospheric transmission does not pass through the lambda/4 wave wafer, the polarizing state does not change, and the signal passes through the polarizing beam splitting piece and will not be reflected to the receiving optical fiber by the polarizing beam splitting piece. Compared with an existing light-path receiving and transmitting integrated DOAS measurement system, the DOAS measurement system can reduce the proportion of stray light inside a telescope and scattered light in the atmospheric background in the measurement signals, also improve the signal to noise ratio of DOAS measurement on the premise that the lighting effect is ensured, and improve the detection precision of the DOAS.

Beam characteristics of fiber-based supercontinuum light sources with mirror- and lens-based beam collimators

Abstract: Commercially available supercontinuum light sources that cover most of the solar spectrum are well suited for instrumentation, where a well-collimated beam with wide spectral coverage is needed. Typically, the optical power is emitted from a single-mode photonic-crystal fiber and the output can either be collimated using a proprietary, permanently integrated, lens-based collimator or with a customer-provided, off-axis parabolic mirror. Here, we evaluate both approaches and conclude that, superior beam quality and collimation over the whole spectral range can be obtained with an off-axis parabolic mirror, however at the price of a more complex and bulky system requiring additional user alignment.

A flux calibration device for the SuperNova Integral Field Spectrograph (SNIFS)

Abstract: Observational cosmology employing optical surveys often require precise flux calibration. In this context we present SNIFS Calibration Apparatus (SCALA), a flux calibration system developed for the SuperNova Integral Field Spectrograph (SNIFS), operating at the University of Hawaii 2.2 m telescope. SCALA consists of a hexagonal array of 18 small parabolic mirrors distributed over the face of, and feeding parallel light to, the telescope entrance pupil. The mirrors are illuminated by integrating spheres and a wavelength-tunable (from UV to IR) light source, generating light beams with opening angles of 1°. These nearly parallel beams are flat and flux-calibrated at a subpercent level, enabling us to calibrate our “telescope + SNIFS system” at the required precision.

Led par lamp in a wireless network environment

Abstract: A flat LED PAR lamp having an antenna secured to the exterior parabolic wall of the glass reflector for use in a wireless network. The interior wall is coated with an aluminized reflective coating that shields the antenna from the internally radiated noise. The aluminized parabolic reflector, together with its companion flat clear lens, is made using a lead-free glass to improve the lumen preservation over the life of the lamp. An efficient LED lamp array is used as the primary source of illumination within the parabolic reflector. Mounted in the base of the LED PAR lamp is the wireless communication and control.