Showing papers on "Parabolic reflector published in 2019"
TL;DR: In this article, a review of the other works carried out in the enhancement of optical and thermal efficiency of the solar PTC is presented along with the economic analysis of the PTC followed by the future research prospects in a parabolic trough collector and economic assessment models.
142 citations
TL;DR: In this paper, a left-hand circular polarized (LHCP) cylindrical waveguide feed horn antenna is proposed, which is used as a feed source for an offset parabolic reflector.
Abstract: A novel $W$ -band left-hand circular polarized (LHCP) cylindrical waveguide feed horn antenna is proposed. The proposed antenna features an inbuilt polarizer structure and a single side-fed linear polarized input to offer symmetric LHCP radiation pattern. The internal polarizer structure consists of nine pairs of circular cavities to generate a circularly polarized wave, eliminating the need for an orthomode transducer or a complex septum. The side-fed horn reduces the overall length by eliminating the rectangular to circular waveguide transition. The proposed horn antenna’s electrical dimension is $7.2\lambda \times 3.9\lambda \times 1.4\lambda $ at 84 GHz. The antenna has impedance matching ( $S_{11}$ below −15 dB) and axial ratio below 1.2 dB from 79.5 to 88 GHz. The horn is used as a feed source for an offset parabolic reflector of 10 cm diameter and small $f/D$ ratio 0.25, which can fit inside a CubeSat. The reflector antenna provides the simulated right-hand circular polarization (RHCP) directivity of 36.6 dBic at 86 GHz with spillover loss of 0.83 dB. The feed reflector assembly is also simulated with the complete aluminum CubeSat chassis. The measurement of the prototyped feed horn and the offset parabolic reflector antenna validates the analysis and simulation results.
32 citations
TL;DR: A darkfield illuminator for reflective FPM consisting of a parabolic mirror and a flat LED panel is proposed, which increases the signal-to-noise ratio of the acquired images because the normal beam of each LED is directed toward the object.
Abstract: Fourier ptychography uses a phase retrieval algorithm to reconstruct a high-resolution image with a wide field-of-view. Reflective-type Fourier ptychographic microscopy (FPM) is expected to be very useful for surface inspection, but the reported methods have several limitations. We propose a darkfield illuminator for reflective FPM consisting of a parabolic mirror and a flat LED panel. This increases the signal-to-noise ratio of the acquired images because the normal beam of each LED is directed toward the object. Furthermore, the LEDs do not have to be far from the object because they are collimated by the parabolic surface before illumination. Based on this, a reflective FPM with a synthesized numerical aperture (NA) of 1.06 was achieved, which is the highest value by reflective FPM as far as we know. To validate this experimentally, we measured a USAF reflective resolution target and reconstructed a high-resolution image. This resolved up to the period of 488 nm, which corresponds to the synthesized NA. Additionally, an integrated circuit was measured to demonstrate the effectiveness of surface inspection of the proposed system.
32 citations
TL;DR: In this paper, a 3D numerical wave tank based on the boundary element method is developed to investigate the wave field around a parabolic breakwater, where a truncated circular cylinder is placed at the focus position of each parabolic opening in front of the breakwater.
29 citations
TL;DR: In this article, an extensive monitoring of a solar thermal parabolic dish system was carried out at the outdoor development center HEnergia of HERA S. p.A. in Forli (Italy).
25 citations
TL;DR: In this paper, the authors investigated the effect of circumsolar radiation on the optimal performance of a coupled parabolic dish and a Stirling heat engine, referred to as the Dish/Stirling system.
23 citations
TL;DR: In this article, an integrated collector storage solar water heater (ICSSWH) equipped with a linear parabolic reflector is designed for integration into a building facade in Algerian Sahara to meet hot water needs of households in winter.
23 citations
TL;DR: In this article, a dual-layer substrate integrated waveguide (SIW) multibeam pillbox antenna with reduced sidelobe level (SLL) is presented, where the feeding network and an antenna array are placed in different layers connected through an SIW parabolic quasi-optical system.
Abstract: In this letter, a dual-layer substrate integrated waveguide (SIW) multibeam pillbox antenna with reduced sidelobe level (SLL) is presented. To avoid the problem of aperture blocking, the feeding network and an antenna array are placed in different layers connected through an SIW parabolic quasi-optical system. Aiming to reduce the SLLs, two extra parabolic reflectors are introduced into the parabolic quasi-optical system placed on both sides of the central parabolic reflector. Moreover, by adding some metal posts in the antenna array section, a further reduction in SLLs can be achieved. The proposed antenna, operating at 28 GHz, has been verified by measurements, showing good performance over a coverage angle of ± 45 ° , and the SLLs of all the beams are lower than −12 dB.
22 citations
TL;DR: In this article, an offset reflector antenna with dual-beam and dual-polarization characteristics is developed to provide the angular diversity function for troposcatter communication system, which consists of a parabolic reflector and a dualbeam feed, two identical Ku-band feed elements are arranged side by side to generate two beams toward the reflector.
Abstract: In this paper, an offset reflector antenna with dual-beam and dual-polarization characteristics is developed to provide the angular diversity function for troposcatter communication system. The antenna system consists of a parabolic reflector and a dual-beam feed. For the dual-beam feed, two identical Ku-band feed elements are arranged side by side to generate two beams toward the reflector. The two beams are substantially nonoverlapping. The feed element is composed of a dielectric rod, a square waveguide, and an ortho-mode transducer. The dielectric rod is effective in reducing the beamwidth of the feed and providing more tapered illumination on the reflector in order to increase the antenna gain. Moreover, the developed antenna is able to produce two independent beams with the vertical and horizontal polarizations. The antenna was fabricated and tested with good agreement between the simulation and measurement results. The measured voltage standing wave ratios of the four feed ports are less than 1.5:1, and the beam separation angle is not more than 0.7° or about one time half-power beamwidth, and the antenna gain is higher than 45 dBi over the operating band from 14.5 to 15.35 GHz.
21 citations
TL;DR: In this paper, the authors present important developments of small point-focusing concentrator in the past decade, which refers to the parabolic dish concentrator, the point-focus Fresnel lens, and the Scheffler reflector.
Abstract: The technology of small point-focusing concentrator of solar energy has been developing rapidly in recent years owing to its compact structure and high collecting efficiency. This report presents important developments of small point-focusing concentrator in the past decade. This kind of solar concentrator refers to the parabolic dish concentrator, the point-focusing Fresnel lens, and the Scheffler reflector. Technological advances of these concentrators and the related performances have been presented. There are three main mirror fabrication technologies for dish concentrator, which are high polishing metal, silver-glass mirror and vacuum-membrane. Polymethyl methacrylate is widely used as material in Fresnel lens. Many scholars have proposed new lens shape to improve the uniformity of focusing. The Scheffler reflector has a characteristic of fixed focus, but its design parameters are not perfect so current research focuses on the theoretical calculation of the mirror. In addition, typical applications of the small point-focusing concentrator in photovoltaic system, solar thermal system, solar chemical system, and day-lighting system are summarized. Upon listing the important publications in open literature, a category of main applications of such kind of solar collector is provided based on the working characteristics of the system.
21 citations
TL;DR: In this paper, a dual-band ring-focus reflector antenna with a reflectarray subreflector is proposed, which has a rotationally symmetric structure and a phase range of approximately 360° in the two frequency bands simultaneously.
Abstract: A dual-band ring-focus reflector antenna with a reflectarray subreflector is proposed in this letter. Reflectarray elements present rotationally symmetric structure and a phase range of approximately 360° in the two frequency bands simultaneously. Parabolic reflector is chosen as the main reflector, and a polygonal reflectarray aperture consisting of 137 elements is designed to emulate a metal subreflector. A ring-focus reflector prototype with subreflectarrays was fabricated and measured. The simulated and measured results of the reflector antenna demonstrate a good availability of the design method for utilizing subreflectarrays into the ring-focus reflector antenna, and a good dual-band performance is shown in gain and bandwidths.
TL;DR: The experimental results verified that chromatic aberration in the laser system was almost fully compensated: the size of laser beam focused by an f/2.42 off-axis parabolic mirror was reduced tremendously from 32×18μm2 to about 4×4 μm2 at full width at half maximum (FWHM).
Abstract: A novel chromatic aberration pre-compensation scheme for ultrashort petawatt laser systems was proposed. The pre-compensation scheme consists of a convex lens, group of concave lenses, and a spherical reflector combined with a conventional vacuum chamber. It provides a versatile method to accurately compensate the chromatic aberration of an entire laser system via controlling the amount of propagation time delay (PTD) induced by the compensator without changing the input and output beam size. A compensator, tailored based on the proposed scheme, was designed and experimentally evaluated for the Shen-Guang-II 5PW (SG-II 5PW) laser system at Shanghai Institute of Optics and Fine Mechanics (SIOM). The experimental results verified that chromatic aberration in the laser system was almost fully compensated: the size of laser beam focused by an f/2.42 off-axis parabolic mirror (OAP) was reduced tremendously from 32×18μm2to about 4×4μm2at full width at half maximum (FWHM). The proposed scheme provides the flexibility to accurately correct chromatic aberration in high-power laser systems within a wide dynamic range.
TL;DR: In this article, a novel parabolic reflector for a Parabolic Trough Collector (PTC) is presented, which contains a varying focal length in lengthwise direction while still maintaining a fixed focal line.
TL;DR: Gas breakdown in the millimetre-wave frequency band is an interesting phenomenon in nonlinear dynamics such as self-organized structure formation and filamentary plasma array formations can influence the energy absorption by the plasma, which is important for engineering applications such as beamed energy propulsion.
Abstract: Gas breakdown in the millimetre-wave frequency band is an interesting phenomenon in nonlinear dynamics such as self-organized structure formation. We observed the transition between two types of filamentary plasma arrays in air discharge driven by a 303-GHz millimetre wave. Plasma is ignited at a parabolic mirror’s focal point in the overcritical condition. One array parallel to the electric field vector appears with a spacing of λ/4 at the focal point. Filaments then separate into plasma lumps ~10 μs after ignition. At 20 μs, a new comb-shaped array grows in the subcritical condition. Filaments are parallel to the incident beam with spacing of 0.96 λ and elongate towards the incident beam. This comb-shaped array appears only in the electric field plane; bulk plasma with a sharp vertex forms in the magnetic field plane. This array is created by a standing wave structure generated by waves diffracted from the plasma surface. Filamentary plasma array formations can influence the energy absorption by the plasma, which is important for engineering applications such as beamed energy propulsion.
TL;DR: This novel design demonstrated high trapping efficiency and strong trapping robustness with a simple optical configuration, and offered a large free space for flexible integration with other measuring techniques, such as optical-trapping Raman spectroscopy, for on-line single particle characterization.
Abstract: We present an advanced optical-trapping method that is capable of trapping arbitrary shapes of transparent and absorbing particles in air. Two parabolic reflectors were used to reflect the inner and outer parts of a single hollow laser beam, respectively, to form two counter-propagating conical beams and bring them into a focal point for trapping. This novel design demonstrated high trapping efficiency and strong trapping robustness with a simple optical configuration. Instead of using expensive microscope objectives, the parabolic reflectors can not only achieved large numerical aperture (N.A.) focusing, but were also able to focus the beam far away from optical surfaces to minimize optics contamination. This design also offered a large free space for flexible integration with other measuring techniques, such as optical-trapping Raman spectroscopy, for on-line single particle characterization.
TL;DR: Shufat et al. as mentioned in this paper proposed a two-axis automated control tracking system for maximum solar energy generation, which tracked the sun in two planes (azimuth and altitude) to move a concentrated parabolic dish system to the direction of ray diffusion of sun radiation.
Abstract: The sun tracking system that lets Parabolic Dish or PV panel orthogonal to the sun radiation during the day, can raise the concentrated sun radiation by up to 40%. The fixed Parabolic Dish cannot generally track the sun trajectory, also the single-axis tracking system can follow the sun in the horizontal direction (azimuth angle), while the two-axis tracker tracks the sun path in both azimuth and altitude angles. Dual axis automated control tracking system, which tracks the sun in two planes (azimuth and altitude) to move a Concentrated Parabolic Dish system to the direction of ray diffusion of sun radiation is studied and designed. The designed tracking system constructed of microcontroller or programmable logic control (PLC) with a digital program that operates sun tracker using driver, gear box to control the angular speed and mechanical torque, supports and mountings. Two steeper motors are modelled to guide the parabolic dish panel perpendicular to the sun's beam. In the present study, simulation scheme of two axis sun tracking system has been developed by operating under Matlab/Simulink. The program models and studies the effectiveness of overall system. The designed tracker has been studied with real data of sun trajectory angles (azimuth and altitude) as well as a Direct Normal Irradiation (DNI) to improve the effectiveness of parabolic dish panel by adding the tracking features to those systems according to the present site. ©2019. CBIORE-IJRED. All rights reserved Article History : Received May 18 th 2018; Received in revised form October 8 th 2018; Accepted January 6 th 2019; Available online How to Cite This Article : Shufat, S.A., Kurt, E, and Hancerliogullari, A. (2019) Modeling and Design of Azimuth-Altitude Dual Axis Solar Tracker for Maximum Solar Energy Generation. Int. Journal of Renewable Energy Development, 8(1), 7-13. https://doi.org/10.14710/ijred.8.1.7-13
TL;DR: In this article, a method for the rapid prototyping of metallic coated poly-methacrylate parabolic reflectors fabricated by stereolithographic 3D printing is presented.
Abstract: Terahertz radiation sources are currently one of the most widely used non-ionizing illumination mechanisms for security applications and also find increasing utilization in quality control of commercial products. Presently, a majority of these applications rely on scanning rather than direct imaging and implicitly suffer from temporal latency due to post processing. The monetary and temporal cost associated with procuring commercially manufactured optics that are suitable for imaging leads to fundamental limitations in the ability to rapidly develop application-specific imaging modalities using terahertz sources. Herein, we show a novel method for the rapid prototyping of metallic coated poly-methacrylate parabolic reflectors fabricated by stereolithographic 3D printing. Images comparing the performance of a commercially available off-axis parabolic reflector to our metalized poly-methacrylate prototype, which was designed to be identical to the commercially available mirror, are subsequently presented. The images show that at 530 GHz it is possible to produce a metalized poly-methacrylate off-axis paraboloid whose spatial beam profile is nearly identical to that of a commercially available equivalent.
TL;DR: In this paper, a ring array concentrator solar furnace was proposed and analyzed for a 5.68mm diameter spherical receiver and large collection area varying from 3.14m2 to 100m2.
TL;DR: In this paper, the effects of using parabolic reflectors instead of flat reflectors on Fresnel solar concentrator have been studied for the first time by ray trace statistical method, local concentration ratio distribution has been determined.
TL;DR: This design can increase transmission efficiency of the optical antenna effectively and in ideal conditions, there is no geometric loss in theory and the transmitting efficiency increases by 24.54% compared with the conventional Cassegrain optical antenna.
Abstract: We propose a novel annular focus antenna with an off-axial parabolic primary mirror and slanting hyperbolic secondary mirror. Ray tracing based on three-dimensional vector reflection theory is utilized to design and analyze the structural parameters of the antenna. In ideal conditions, there is no geometric loss in theory and the transmitting efficiency increases by 24.54% compared with the conventional Cassegrain optical antenna. The transmitting efficiency is also calculated in the conditions of off-axial and on-axial defocus. The simulated results demonstrate that this design can increase transmission efficiency of the optical antenna effectively.
TL;DR: In this paper, a four-rod solar pumping concept was proposed for the significant improvement in TEM00-mode solar laser performance, where a quadrangular pyramidal reflector was used to separate the focused solar rays from a 2.0m diameter parabolic mirror into four focal spots.
Abstract: A four-rod solar pumping concept is proposed for the significant improvement in TEM00-mode solar laser performance. A quadrangular pyramidal reflector is used to separate the focused solar rays from a 2.0-m diameter parabolic mirror into four focal spots. Four laser heads, each one consisting of a double-stage biconical lens/conical pump cavity and a small diameter Nd:YAG rod, are placed at each of the four focal zones. TEM00-mode laser output of 7.22 W is numerically obtained from each rod, resulting in 28.9 W (4 × 7.22 W) total TEM00-mode power from the four-rod scheme with 9.41 W / m2 collection efficiency. This value is 2.5 times more than that of the numerically calculated laser power collection efficiency from a single-rod pumped by the same parabolic mirror. A brightness conversion efficiency of 0.86% is achieved. Substantial improvements in TEM00-mode solar laser stability and thermal performance are also numerically demonstrated.
TL;DR: In this paper, a deployable parabolic mesh reflector was used to reduce the size and weight of the small space-borne SAR C-band antenna and operate at low Earth orbital altitudes, which is a wrap-rib center-fed parabolic reflector with dedicated receiving and transmitting feeds.
13 Mar 2019
TL;DR: In this paper, a parabolic lens, fabricated using focused ion beam milling, with a diameter of 15 μm and height of 5 μm, was embedded 6.5 μm below the endfacet of the optical fiber.
Abstract: This work demonstrates an approach for simplifying fiber-to-chip (edge coupling) packaging by virtually eliminating the longitudinal alignment procedure (also increasing compactness and efficiency) through a fiber lens embedded into the structure of the fiber itself. A parabolic lens, fabricated using focused ion beam milling, with a diameter of 15 μm and height of 5 μm, was embedded 6.5 μm (the working distance of the parabolic lens) below the endfacet of the fiber. The lens focuses a 10.4 μm fiber mode into a spot size of 2.6 μm on the surface of an SMF-28e single-mode optical fiber. The properties of the fabricated lens were studied using the three-dimensional finite-difference time-domain numerical method, and the optimal parameters for maximizing the coupling conditions were extracted. The conversion loss of the lens is estimated to be around . The insertion loss and lateral alignment of the proposed parabolic lens is comparable to a commercial lensed fiber, while directly ensuring the longitudinal alignment, easing the angular alignment, and providing additional mechanical and environmental robustness.
TL;DR: A novel concept to a large improvement in TEM00-mode side-pumped solar laser collection, conversion efficiencies, and brightness figure of merit by pumping two thin laser rods simultaneously, each rod being pumped by half of the solar collector area instead of today's one thick rod scheme.
Abstract: We propose here a novel concept to a large improvement in TEM00-mode side-pumped solar laser collection, conversion efficiencies, and brightness figure of merit by pumping two thin laser rods simultaneously, each rod being pumped by half of the solar collector area instead of today's one thick rod scheme pumped by the full solar collector area. A semicylindrical fused silica lens allows an efficient focusing of the concentrated solar power from the focal zone of the parabolic mirror into the two thin laser rods mounted within two compound parabolic concentrator-semicylindrical pump cavities within the same laser head. 17.2 W continuous-wave TEM00-mode solar laser power was numerically calculated, corresponding to 11.0 W/m2 solar laser collection efficiency, 1.31% incoming solar power-to-TEM00-mode laser power conversion efficiency, and 14.3 W brightness figure of merit, being 1.39, 1.23, and 2.21 times, respectively, higher than the previous state-of-the-art experimental records.
TL;DR: The rigorous diffraction integrals that generate vector fields within and outside the focus arising from a collimated beam incident on an idealized parabolic mirror were derived in detail and it was shown that there are significant differences in the vector diffraction characterizations between on- and off-axis parabolic mirrors.
Abstract: In this paper, we present a systematic investigation of the characterization of tightly focused vector fields formed by an off-axis parabolic mirror. Based on the Stratton-Chu integral of Green’s theorem, the rigorous diffraction integrals that generate vector fields within and outside the focus arising from a collimated beam incident on an idealized parabolic mirror were derived in detail. In addition, explicit analytical expressions for the far-field vector diffraction electric and magnetic fields suitable for an off-axis parabolic mirror were also obtained. It is shown that there are significant differences in the vector diffraction characterizations between on- and off-axis parabolic mirrors. When the off-axis rate is greater than 4, the longitudinal field is predominant, and the maximum peak intensity ratio between the longitudinal field and the transverse field at the focus is approximately 103. This property is valuable for all applications in which a strong longitudinal field component is desirable. The effective focal length increases with increasing off-axis rate, and the depth of focus and the convergence angle of the focused beam are strongly dependent onf′/2ω: smaller values of f′/2ω lead to shorter focal depths and larger beam convergence (or tighter focusing).
TL;DR: In this article, a matched primary feed based on printed patch antennas was proposed to reduce the cross-polarizing effects of offset parabolic reflector antennas to well below −32 dB at both asymmetry and diagonal planes.
Abstract: The depolarizing effects of offset parabolic reflector antennas are addressed through the use of an over-moded primary feed based on printed patch antennas. The modes of interest are the TM11 and TM21 modes of circular microstrip patch antennas. It will be shown that the proposed matched feed is reasonably comparable with its waveguide-type counterparts, as it is capable of reducing the unwanted cross polarization of offset reflector antennas to well below −32 dB at both asymmetry and diagonal planes.
TL;DR: In this article, the use of reflectarrays is proposed to increase D without changing the feed location, where the reflecting surface is loaded with dielectric panels where the phase of the reflected field is controlled using continuous metal strips of variable widths.
Abstract: Cylindrical parabolic reflectors have been widely used in those applications requiring high gain antennas. Their design is dictated by the geometric relation of the parabola, which relate the feed location, f, to the radiating aperture, D. In this work, the use of reflectarrays is proposed to increase D without changing the feed location. In the proposed approach, the reflecting surface is loaded with dielectric panels where the phase of the reflected field is controlled using continuous metal strips of variable widths. This solution is enabled by the cylindrical symmetry and, with respect to rectangular patches or to other discrete antennas, it provides increased gain. The proposed concept has been evaluated by designing a Ka-band antenna operating in the Rx SatCom band (19–21 GHz). A prototype has been designed and the results compared with the ones of a parabolic cylindrical reflector using the same feed architecture. Simulated results have shown how this type of antenna can provide higher gain in comparison to the parabolic counterpart, reaching a radiation efficiency of 65%.
TL;DR: In this paper, an aspherical mirror was proposed to produce light fields with uniform long focal depth by the energy conservation equation and the principle of equal optical path, and the focusing characteristics of the novel mirror were studied in detail by numerical simulations based on scalar diffraction theory.
TL;DR: A scheme for designing a novel optical receiving antenna to extend the field of view, receive higher power, and reduce the received-energy spot area for indoor visible light communication (VLC).
Abstract: A scheme for designing a novel optical receiving antenna is proposed to extend the field of view, receive higher power, and reduce the received-energy spot area for indoor visible light communication (VLC). ProE is used to model the antenna, while TracePro and Matlab are employed for simulations. Firstly, the lens wall of a compound parabolic concentrator with a certain rotation angle and thickness is obtained through rotating the parabolic reflector cross-section reference curve. Furthermore, a novel optical receiving antenna is designed in combination with the advantages of the lens-walled CPC and the spherical lens. Then, the Taguchi methodology and ANOVA technique are utilized to optimize the structure parameters of the receiving antenna. Finally, an indoor VLC system model is established and the channel performance is analyzed. Simulation results show that the designed antenna achieves the following performances: optical gain of 21.53, field of view of 45°, and spot size of 3 mm. The received power is 9.5532 dBm, and the SNR is 86.2526 dB, which further confirms that the designed optical receiving antenna is suitable for indoor VLC systems.