Littérature scientifique sur le sujet « Antenna surface illumination »
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Articles de revues sur le sujet "Antenna surface illumination"
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Shaffer, David B., et John M. Gipson. « A Portable Holographic Antenna Measurement System ». International Astronomical Union Colloquium 131 (1991) : 94–97. http://dx.doi.org/10.1017/s0252921100013129.
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AbstractInterferometrics has developed a portable holographic antenna measurement system. The system is comprised of a small interferometer which uses satellite signals to measure the complex beam pattern of the antenna under test. A PC controls all aspects of data collection and analysis. The system produces maps of surface profile errors and the illumination power in reflector antennas.
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Baek, Jong Jin, Se Woong Kim et Youn Tae Kim. « Camera-Integrable Wide-Bandwidth Antenna for Capsule Endoscope ». Sensors 20, no 1 (31 décembre 2019) : 232. http://dx.doi.org/10.3390/s20010232.
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This paper presents a new antenna design for a capsule endoscope. The proposed antenna comprises a camera hole and meandered line. These features enable the antenna to be integrated on the same side as the camera, within the capsule endoscope. Moreover, light-emitting diodes can be mounted on the surface of the antenna for illumination. The antenna achieves a wide bandwidth, despite the small size owing to its meandered line structure.
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Tripon-Canseliet, Charlotte, Cristian Della Giovampaola, Nicolas Pavy, Jean Chazelas et Stefano Maci. « Optically Controlled Gain Modulation for Microwave Metasurface Antennas ». Sensors 24, no 6 (16 mars 2024) : 1911. http://dx.doi.org/10.3390/s24061911.
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Over the past decade, metasurfaces (MTSs) have emerged as a highly promising platform for the development of next-generation, miniaturized, planar devices across a wide spectrum of microwave frequencies. Among their various applications, the concept of MTS-based antennas, particularly those that are based on surface wave excitation, represents a groundbreaking advancement with significant implications for communication technologies. However, existing literature primarily focuses on MTS configurations printed on traditional substrates, largely overlooking the potential benefits of employing photosensitive substrates. This paper endeavors to pioneer this novel path. We present a specialized design of a modulated MTS printed on a silicon substrate, which acts as a photosensitive Ka-band surface wave antenna. Remarkably, the gain of this antenna can be time-modulated, achieving a variance of up to 15 dB, under low-power (below 1 W/cm²) optical illumination at a wavelength of 971 nm. This innovative approach positions the antenna as a direct transducer, capable of converting an optically modulated signal into a microwave-modulated radiated signal, thus offering a new dimension in antenna technology and functionality.
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Quintero-Torres, Rafael, Jorge Luis Domínguez-Juárez, Mariia Shutova et Alexei V. Sokolov. « Usability of Tilted Plasmon Antenna with Structured Light ». Photonics 8, no 11 (9 novembre 2021) : 504. http://dx.doi.org/10.3390/photonics8110504.
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We study the effect of oblique illumination on the functioning of a plasmonic nanoantenna for chiral light. The antenna is designed to receive a structured beam of light and produce a nanosized near-field distribution that possesses nonzero orbital angular momentum. The design consists of metal (gold) microrods laid on a dielectric surface and is compatible with well-developed nanofabrication techniques. Experimental arrangements often require such an antenna to operate in a tilted geometry, where input light is incident on the antenna at an oblique angle. We analyze the limitations that the angled illumination imposes and discuss approaches to mitigate these limitations. Through our numerical simulations, we find that tilt angles require modifications to the antenna design. Our analysis can guide current and future experimental configurations to push the limits of resolution and sensitivity.
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Lampe, Bernhard, Klaus Holliger et Alan G. Green. « A finite‐difference time‐domain simulation tool for ground‐penetrating radar antennas ». GEOPHYSICS 68, no 3 (mai 2003) : 971–87. http://dx.doi.org/10.1190/1.1581069.
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The generation and recording of electromagnetic waves by typical ground‐penetrating radar (GPR) systems are complex phenomena. To investigate the characteristics of typical GPR antennas operating in diverse environments, we have developed a versatile and efficient simulation tool. It is based on a finite‐difference time‐domain (FDTD) approximation of Maxwell's equations that lets one simulate the radiation characteristics of a wide variety of typical surface GPR antenna systems. The accuracy of the algorithm is benchmarked and validated with respect to laboratory measurements for comparable antenna systems. Computed radiation patterns demonstrate that the illumination of the subsurface in the near‐ to intermediate‐field range varies significantly according to how the antenna is designed. Our models show the effects of varying the shapes of the antennas, adding shielding (metal box with and without absorbing material and with and without resistive loading), adding a receiver antenna, and changing the soil conditions. Given the flexibility of this modeling software, we anticipate that it will be helpful in designing GPR surveys and new GPR systems with arbitrary planar structures. It will also be useful in interpreting certain GPR data sets.
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Kartsan, Igor, et Aleksander Zhukov. « Radar sensing of the sea surface using small spacecraft ». InterCarto. InterGIS 28, no 1 (2022) : 383–93. http://dx.doi.org/10.35595/2414-9179-2022-1-28-383-393.
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The possibility of using a constellation of small spacecraft as receiving satellites, when “highlighting” the sea surface from existing (navigational, communication) or specially created spacecraft—to form a wide-area (about 1 000 km) radar survey zone at a given resolution (about 10 m)—is under consideration. Such a constellation could provide operational monitoring of fast-moving atmospheric cyclones, measuring directly the parameters of storm waves (altitude and orbital velocity)—which would replace the existing constellation of microwave scatterometers, providing operational monitoring of the World Ocean surface in the 3 H (H—altitude of the satellite’s orbit) field of view with a resolution of about 10 km—but with calibration of the received images by wind speed and direction, which leads to huge errors when trying to introduce altitude calibration in the Small spacecraft have many advantages over large satellites. For example, they are relatively inexpensive to build, take minimal time from design to launch, are easily modified to solve a specific problem, and create less radio interference. The approach under consideration consists in redistribution of tasks to be solved between the constellation of satellites in orbit. High orbiting navigation satellites, for example, can be used as transmitter carriers (of the illumination of the surface) that use the necessary broadband signal with acceptable periodicity. Receivers of reflected signals are placed on board small spacecraft, and at formation of wide-band radar image of sea surface with necessary resolution ∼10 m (that only on order exceeds acceptable on small spacecraft size of receiving antennas)—in flight direction is necessary to use synthesized aperture of receiving antenna. This work has the character of “staged” research.
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Орлов, В., О. Коркін, С. Ковалішин et О. Наумов. « РОЗТАШУВАННЯ РОБОТИЗОВАНИХ КОМПЛЕКСІВ ПРОТИРАКЕТНОЇ ОБОРОНИ НА БЕЗПІЛОТНОМУ ПОВІТРЯНОМУ ТРАНСПОРТІ ». Collection of scientific works of Odesa Military Academy, no 20 (14 décembre 2023) : 108–16. http://dx.doi.org/10.37129/2313-7509.2023.20.108-116.
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Objects of critical infrastructure of Ukraine need a multi-level anti-missile defense system, which should protect against various types of missiles with a flight range of several tens to several hundreds of kilometers. Timely detection of missiles allows for a number of measures aimed at interception and destruction of targets, the use of radio-electronic warfare, the installation of interfering and obstructing obstacles in various ranges of radio waves, as well as the inclusion of optical and thermal traps. The use of robotic complexes placed on aerostats increases the effectiveness of modern surface-to-air missile system (SAMS) many times over in the fight against low-flying targets with massed strikes of cruise missiles. The location of radar at an altitude of several kilometers ensures the detection range of low-flying targets several times greater than that of ground-based radar. This is of particular importance for SAMS when firing at targets beyond the radio horizon. The transfer of data about the location of the target from the radar of the air carrier to the air defense system and its illumination and guidance radar (at least the approximate location) provides the opportunity to bring the anti-missile to the point of inclusion of its homing head. It is proposed to modernize the radar with an active phased antenna array used on fighters to increase the range and installation on airships and balloons. This will ensure the effectiveness of defense against missile attacks, detection and tracking of up to 100 targets at distances of about 40...400 km. At the same time, the weight of the radar within the range of 200...500 kg and the dimensions of the antennas up to 1 meter are permissible for installation on large balloons. Countries for which attacks of various types of missiles are a real threat need a multi-level anti-missile system, in particular, using robotic complexes placed on air carriers. Keywords: anti-missile defense, radar station, balloon, airship.
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Sidibe, Alassane, Alexandru Takacs, Gaël Loubet et Daniela Dragomirescu. « Compact Antenna in 3D Configuration for Rectenna Wireless Power Transmission Applications ». Sensors 21, no 9 (4 mai 2021) : 3193. http://dx.doi.org/10.3390/s21093193.
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This work presents methods for miniaturizing and characterizing a modified dipole antenna dedicated to the implementation of wireless power transmission systems. The antenna size should respect the planar dimensions of 60 mm × 30 mm to be integrated with small IoT devices such as a Bluetooth Lower Energy Sensing Node. The provided design is based on a folded short-circuited dipole antenna, also named a T-match antenna. Faced with the difficulty of reducing the physical dimensions of the antenna, we propose a 3D configuration by adding vertical metallic arms on the edges of the antenna. The adopted 3D design has an overall size of 56 mm × 32 mm × 10 mm at 868 MHz. Three antenna-feeding techniques were evaluated to characterize this antenna. They consist of soldering a U.FL connector on the input port; vertically connecting a tapered balun to the antenna; and integrating a microstrip transition to the layer of the antenna. The experimental results of the selected feeding techniques show good agreements and the antenna has a maximum gain of +1.54 dBi in the elevation plane (E-plane). In addition, a final modification was operated to the designed antenna to have a more compact structure with a size of 40 mm × 30 mm × 10 mm at 868 MHz. Such modification reduces the radiation surface of the antenna and so the antenna gain and bandwidth. This antenna can achieve a maximum gain of +1.1 dBi in the E-plane. The two antennas proposed in this paper were then associated with a rectifier to perform energy harvesting for powering Bluetooth Low Energy wireless sensors. The measured RF-DC (radiofrequency to direct current) conversion efficiency is 73.88% (first design) and 60.21% (second design) with an illuminating power density of 3.1 µW/cm2 at 868 MHz with a 10 kΩ load resistor.
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Zaman, Mohammad Asif, et Md Abdul Matin. « A New Method of Designing Circularly Symmetric Shaped Dual Reflector Antennas Using Distorted Conics ». International Journal of Microwave Science and Technology 2014 (17 décembre 2014) : 1–8. http://dx.doi.org/10.1155/2014/849194.
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A new method of designing circularly symmetric shaped dual reflector antennas using distorted conics is presented. The surface of the shaped subreflector is expressed using a new set of equations employing differential geometry. The proposed equations require only a small number of parameters to accurately describe practical shaped subreflector surfaces. A geometrical optics (GO) based method is used to synthesize the shaped main reflector surface corresponding to the shaped subreflector. Using the proposed method, a shaped Cassegrain dual reflector system is designed. The field scattered from the subreflector is calculated using uniform geometrical theory of diffraction (UTD). Finally, a numerical example is provided showing how a shaped subreflector produces more uniform illumination over the main reflector aperture compared to an unshaped subreflector.
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Gupta, Akash Kumar, Harish Chandra Mohanta, P. Satish Rama Chowdary, M. Vamshi Krishna et Heba G. Mohamed. « Design and Analysis of Fractal-Shaped High-Impedance Surface Unit Cell Characteristics ». Fractal and Fractional 7, no 6 (14 juin 2023) : 472. http://dx.doi.org/10.3390/fractalfract7060472.
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Fractal geometries consistently provide solutions to several electromagnetic design problems. In this paper, fractal geometries such as Hilbert and Moore curves are used to design efficient High-Impedance Surfaces. Modern communication devices have many sensors that are needed to communicate wirelessly. The critical component of wireless communications is antennas. Planar microstrip patch antennas are popular due to their low profile, compactness, and good radiation characteristics. The structural disadvantages of microstrip antennas are that they have surface waves that propagate over the ground plane. High-Impedance Surface (HIS) planes are a prominent solution to minimize and eliminate surface waves. The HIS structures behave as active LC filters that suppress surface waves at their resonance frequency. The resonance frequency of the structure is obtained by its LC equivalent or by analyzing the reflection phase characteristics. This work presents conventional HIS structures similar to mushroom HIS and fractal HIS such as Hilbert curve and Moore curve HIS. The HIS reflection phase characteristics are obtained by applying periodic boundary conditions with plane wave illumination. The results were obtained in terms of the reflection phase angle. The conventional mushroom structures show narrow band characteristics at given dimensions of 10 mm × 10 mm and 20 mm × 20 mm. These structures are helpful in the replacement of PEC ground planes for patch antennas under sub-6 GHz. The Hilbert and Moore fractals are also designed and have a multiband response that can be useful for L, S, and C band applications. Another design challenge of HIS is protrusions, which make design difficult. The work also presents the effect of having vias and the absence of vias on reflection phase characteristics. The response shows the least and no significant effect of vias under the x-band operation.
Thèses sur le sujet "Antenna surface illumination"
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Chalumyan, Taguhi. « Contribution à la calibration des antennes actives pour applications radar ». Electronic Thesis or Diss., Paris, ENST, 2017. http://www.theses.fr/2017ENST0032.
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Les travaux effectués pendant cette thèse portent sur le développement d’une nouvelle méthode de calibration des antennes actives pour applications radars. La méthode de calibration, détaillée au cours de ce manuscrit, prend en compte les effets de bord et de couplage entre les éléments rayonnants du réseau, en les intégrant dans le procédé de calibration ; de plus, elle permet d’éviter les dégradations de diagramme de rayonnement qui peuvent être causés par les désadaptions lors d’un pointage et/ou d’une pondération. Le champ lointain est calculé par Matlab à partir des données du champ proche calculé par HFSS. Ensuite par rétro-propagation des données de champ lointain, on calcule l’éclairement de la surface de l’antenne. A partir d’un schéma électrique équivalent du réseau d’antennes, on optimise avec ADS les valeurs de l’éclairement afin d’obtenir le diagramme de rayonnement souhaité. Les valeurs résultantes correspondent aux constantes de calibration du réseau. Cette approche a le double avantage de permettre de traiter ensemble les informations de la partie circuit et de la partie rayonnante de l’antenne et d’obtenir les coefficients de calibration de manière automatique en respectant la réalité de l’antenne. Cette méthode peut être appliquée aux antennes réelles afin d’obtenir un diagramme de rayonnement souhaité. Le modèle numérique peut être amélioré en y intégrant les schémas électriques équivalents des circuits RFThe main goal of this thesis is to develop a new active antennas calibration method for radar application. The calibration method takes into account the edge effects and the coupling between the antenna radiating elements. Moreover, this method allows avoiding the degradations of the antenna radiation pattern caused by mismatch produced during a scanning and/or a weighting process. HFSS software is used to provide near-field electromagnetic numerical simulations. Matlab is used for far-field calculation from the near-field data; and also for the calculation of the illumination on the antenna surface by back-propagation of far-field datas. The calibration process is performed by an optimization process by means of ADS software. An equivalent schematic is built in it, in order to obtain desired radiation pattern which corresponds to the illumination on the antenna surface. The presented approach allows full simulation of RF circuits and radiation of the antenna array together and to get the calibration coefficients automatically. The model can be applied to the real antennas in order to get the desired pattern. The antenna equivalent model can be improved by adding RF schematic in it
Actes de conférences sur le sujet "Antenna surface illumination"
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Ataloglou, Vasileios G., et George V. Eleftheriades. « Efficient Aperture Illumination and Beamforming with Huygens’ Metasurfaces Exciting Surface Waves ». Dans 2021 15th European Conference on Antennas and Propagation (EuCAP). IEEE, 2021. http://dx.doi.org/10.23919/eucap51087.2021.9410963.
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Barbuto, Mirko, Zahra Hamzavi-Zarghani, Mohsen Karamirad, Michela Longhi, Alessio Monti, Davide Ramaccia, Luca Stefanini et al. « Reflective Intelligent Surfaces : Reducing Complexity by Controlling the Illuminating Field ». Dans 2024 18th European Conference on Antennas and Propagation (EuCAP). IEEE, 2024. http://dx.doi.org/10.23919/eucap60739.2024.10501662.
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Jasmin, Serge, et Nakita Vodjdani. « Microwave Waveguide Photodiodes with Distributed Absorption for High Power Applications ». Dans The European Conference on Lasers and Electro-Optics. Washington, D.C. : Optica Publishing Group, 1996. http://dx.doi.org/10.1364/cleo_europe.1996.ctho5.
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The wide developement of analog radio frequency (RF) optical fiber links for optically fed wireless communication systems and phased array antennas is partly conditioned by the availability of high speed, high efficiency photodetectors which can also deliver high RF power. Lumped or travelling-wave waveguide PIN photodetectors (WGPDs) [1,2] can achieve both high quantum efficiency and high bandwidth without any limitations in bandwidth efficiency product as in conventional PD. However in this WGPDs, carriers are generated in the first ten microns. As a consequence, under high illumination, the high photocarriers density in this small surface area, by space charge effects, modifies the internal electric field which in turn governs the carriers transport. This field screening induces non linearities of the electrical response of the PD for high optical power, and limits the maximum RF power which can be delivered. For higher power capabilities, diluted travelling-wave detectors (TWDs) have been proposed [3,4]. In order to further improve the power handling of the detectors and reduce the space charge effects, we propose and analyze a new microwave WGPD which distributes absorption over the maximum junction area available. The structure is based on a diluted singlemode WG with coupling and quantum efficiencies > 90% and can handle both high optical and electrical power. The photocarriers density is maintained constant along the whole propagation length of the diode (instead of being exponential) by controling and tailoring the modal absorption coefficient αΓ(z) along the axis of propagation (Fig.l). This design applies to lumped WGPDs as well as TWDs. For the distributed absorption WGPD presented here, the depleted region consists of a thin InGaAsP active layer sandwiched between transparent WG and contact layers and αΓ(z) can be varied by a factor of 10 by changing the WG ridge width from 2 to 4 µm. For a same junction area, the maximum RF output power can be 4 to 9 times higher for distributed absorption WGPDs as compared to diluted WGPDs [3,4] (lumped or TWDs). The structures are compared by using a drift-diffusion model which takes into account the heterointerfaces, device depolarization due to current flow in the load circuit and calculates the electric field in the depleted region in the linear regime (50 < E< 250kV/cm). At a given cut off frequency the figure of merit F is defined as the ratio of the maximum RF power to the incident optical power. F is optimized by choosing the maximum depleted region thickness (transit time limitation), the maximum junction area (RC time constant limitation for lumped detectors and 5 times more for TWDs) and by varying the reverse voltage and the optical power. Details of the design and performances of distributed absorption WGPD with coplanar transmission line will be presented in the conference.