New Circularly Polarized Matrix Antenna For Space Applications

International audiencethis paper presents a new electromagnetic approach of matrix antenna, specialized for circularly polarized space applications. The design of the proposed antenna matrix is based on small pixels which generate circular polarization field. The concept of the pixels is well demonstrated as a patent and verified for the use in antenna arrays. The design will be used for several space applications with directive and wide angle beams. Index Terms—antenna array, axial ratio, beam forming, Isoflux, Electromagnetic band gap material EBG, Frequency selective surface FSS

Miniaturisation d'antennes en bande VHF pour applications spatiales

Le développement de l électronique embarquée et miniaturisée est pleinement d actualité de nos jours, dans les domaines tels que l armement, la médecine, et les télécommunications. La miniaturisation des antennes large-bande, opérationnelles sur plus d une décade, présentent un défi particulier. Ces travaux de thèse proposent de travailler sur la miniaturisation d une antenne spirale, afin d en réduire l encombrement, à savoir son diamètre, tout en conservant au mieux ses caractéristiques de rayonnement et polarisation intrinsèques. Cette recherche sera appliquée à la bande des Très hautes Fréquence (Very High Frequencies VHF), allant de 30MHz à 300MHz La géométrie inédite proposée consiste à associer à une antenne spirale un ensemble d anneaux résonnants, dont le diamètre n excède pas celui de la spirale, et permettant de diminuer la fréquence basse de fonctionnement. Pour un ensemble de cinq anneaux associé à la spirale, la réduction de la fréquence basse de fonctionnement est de plus de 30%. Pour deux antennes spirales de même fréquence basse de fonctionnement, l antenne miniaturisée a donc un diamètre réduit de 30%, soit une surface réduite de 50%. Les performances de l état de l art d après lesquelles les réductions sur le diamètre des antennes spirales n excèdent pas 15% sont donc dépassées. De plus, d après cet état de l art, les méthodes de réduction appliquées aux antennes large bande dégradent en général le gain et l axial ratio dans les bandes basses de fréquences de fonctionnement. La méthode proposée permet de conserver l efficacité de l antenne, voire de l augmenter, dans les fréquences proches de la fréquence basse de fonctionnement. Le rayonnement de l antenne spirale miniaturisée dans la bande passante de l antenne sans anneaux n est pour autant pas modifiée. Ces résultats très encourageant ont été confirmés par la mesure d antennes spirales miniaturisées, réalisées pour un diamètre de 8cm et de 1m : une réduction de 30% du diamètre sans dégradation du rayonnement a été observée. Les mesures ont par ailleurs donné lieu à l étude de la réalisation d une antenne en bande VHF, avec pour implication les problématiques de réalisation (masse, encombrement, résistance mécanique) et de mesure (isolation, effets parasites en VHF avec une longueur d onde de 4m).Miniaturizing electronic devices is a great challenge in crucial research domain such as defense, medicine, and telecommunications. Wideband antenna miniaturization operating on more than a decade is a particular issue. This thesis presents an original method for miniaturizing a spiral antenna, reducing its diameter while keeping its bandwidth, its radiating performances and its axial ratio characteristics. This method is applied to UHF spiral antenna (from 750MHz) and VHF antenna (from 75MHz). The new geometry adds stacked resonant rings to an Archimedean spiral antenna. Their diameter are the same, hence no rise of the antenna diameter. For a 5-ring spiral antenna, the lowest operating frequency reduction is higher than 30%. That is equivalent to a 30% reduction of the diameter for two antennas sharing the same lowest operating frequency, hence a 50% reduction of the area of the antenna. These reduction factors surpass the reduction factors of the state of art of 15%. Besides, according to the state of art, the miniaturizing techniques imply some degradation of the gain and axial ratio performances at the lowest operating frequencies. The new method improves on the other hand these characteristics at these frequencies. At higher frequencies, the rings do not interfere with the matching of neither the spiral antenna nor its radiation characteristics. These results were validated by fabricated antenna measurements. A 30% reduction of the diameter was obtained on a 5-ring-8cm-large antenna as well as on a 5-ring-1m-large antenna. No impairment was noticed on the radiation of the antennas, even at the lowest operating frequencies. The thesis also discusses the difficulties which came in addition for the fabrication (mass, size and mechanical resistance) and measurement (radiation interferences and measurement isolation the wavelength being 4m) of the VHF antenna.TOULOUSE-INP (315552154) / SudocSudocFranceF

Mobile Asteroid Surface Scout (MASCOT) - Design, Development and Delivery of a Small Asteroid Lander Aboard Hayabusa2

MASCOT is a small asteroid lander launched on December 3rd, 2014, aboard the Japanese HAYABUSA2 asteroid sample-return mission towards the 980 m diameter C-type near-Earth asteroid (162173) 1999 JU3. MASCOT carries four full-scale asteroid science instruments and an uprighting and relocation device within a shoebox-sized 10 kg spacecraft; a complete lander comparable in mass and volume to a medium-sized science instrument on interplanetary missions. Asteroid surface science will be obtained by: MicrOmega, a hyperspectral near- to mid-infrared soil microscope provided by IAS; MASCAM, a wide-angle Si CMOS camera with multicolour LED illumination unit; MARA, a multichannel thermal infrared surface radiometer; the magnetometer, MASMAG, provided by the Technical University of Braunschweig. Further information on the conditions at or near the lander‘s surfaces is generated as a byproduct of attitude sensors and other system sensors. MASCOT uses a highly integrated, ultra-lightweight truss-frame structure made from a CFRP-foam sandwich. It has three internal mechanisms: a preload release mechanism, to release the structural preload applied for launch across the separation mechanism interface; a separation mechanism, to realize the ejection of MASCOT from the semi-recessed stowed position within HAYABUSA2; and the mobility mechanism, for uprighting and hopping. MASCOT uses semi-passive thermal control with Multi-Layer Insulation, two heatpipes and a radiator for heat rejection during operational phases, and heaters for thermal control of the battery and the main electronics during cruise. MASCOT is powered by a primary battery during its on-asteroid operational phase, but supplied by HAYABUSA2 during cruise for check-out and calibration operations as well as thermal control. All housekeeping and scientific data is transmitted to Earth via a relay link with the HAYABUSA2 main-spacecraft, also during cruise operations. The link uses redundant omnidirectional UHF-Band transceivers and patch antennae on the lander. The MASCOT On-Board Computer is a redundant system providing data storage, instrument interfacing, command and data handling, as well as autonomous surface operation functions. Knowledge of the lander’s attitude on the asteroid is key to the success of its uprighting and hopping function. The attitude is determined by a threefold set of sensors: optical distance sensors, photo electric cells and thermal sensors. A range of experimental sensors is also carried. MASCOT was build by the German Aerospace Center, DLR, with contributions from the French space agency, CNES. The system design, science instruments, and operational concept of MASCOT will be presented, with sidenotes on the development of the mission and its integration with HAYABUSA2

К проблеме социальной эффективности инноваций в профессиональном образовании

Movile Cave, Romania, is an unusual underground ecosystem that has been sealed off from the outside world for several million years and is sustained by non-phototrophic carbon fixation. Methane and sulfur-oxidising bacteria are the main primary producers, supporting a complex food web that includes bacteria, fungi and cave-adapted invertebrates. A range of methylotrophic bacteria in Movile Cave grow on one-carbon compounds including methylated amines, which are produced via decomposition of organic-rich microbial mats. The role of methylated amines as a carbon and nitrogen source for bacteria in Movile Cave was investigated using a combination of cultivation studies and DNA stable isotope probing (DNA-SIP) using 13C-monomethylamine (MMA). Two newly developed primer sets targeting the gene for gamma-glutamylmethylamide synthetase (gmaS), the first enzyme of the recently-discovered indirect MMA-oxidation pathway, were applied in functional gene probing. SIP experiments revealed that the obligate methylotroph Methylotenera mobilis is one of the dominant MMA utilisers in the cave. DNA-SIP experiments also showed that a new facultative methylotroph isolated in this study, Catellibacterium sp. LW-1 is probably one of the most active MMA utilisers in Movile Cave. Methylated amines were also used as a nitrogen source by a wide range of non-methylotrophic bacteria in Movile Cave. PCR-based screening of bacterial isolates suggested that the indirect MMA-oxidation pathway involving GMA and N-methylglutamate is widespread among both methylotrophic and non-methylotrophic MMA utilisers from the cave

Etude de nouveaux concepts de systèmes antennaires de radiogoniométrie en polarisation "H" et "V" dans les bandes "VHF" et "UHF"

L'objectif de ce travail est d'étudier et de réaliser de nouveaux concepts de systèmes antennaires à faible encombrement, permettant de mesurer des signaux de polarisations diverses pour des applications de radiogoniométrie dans les bandes V/UHF. Une première partie a été consacrée à l'étude théorique des performances de radiogoniométrie de différents systèmes antennaires à partir de la borne de Cramer-Rao réaliste des directions d'arrivées de signaux. Le deuxième point majeur de cette étude concerne les capteurs élémentaires dont le choix a été fortement influencé par l'application finale du système : la radiogoniométrie sur porteur mobile. Ces antennes ont ensuite été associées en réseau de manière à obtenir une couverture radioélectrique omnidirectionnelle. Une troisième partie a été consacrée à l'installation, à la mise en œuvre et à l'estimation des performances des deux systèmes antennaires dans leur environnement réel, à savoir placés sur le toit d'un véhicule.The goal of this work is to study and realize new small antenna systems to measure diversely polarized signals for radio direction finding applications in the V/UHF bands. The first part was focused on the theoretical study of radio direction finding performances of two différent systems using the "realistic" Cramer-Rao lower bound of the signal's directions of arrival. The second point of the study concern the antenna's choice and design, influence by the final application: radio direction finding on vehicle. Then, these antennas have been associated to realize a array with an omnidirectionnal coverage. The final part of this work concerns the antenna installation and the radio direction finding performances in real environment : on the roof of a vehicle.LIMOGES-BU Sciences (870852109) / SudocSudocFranceF

Q Factor-Based Electrically Small Antenna Radiation Efficiency Measurement Using the Wheeler Cap

International audienceIn this letter, a small antenna radiation efficiency measurement method is presented. The method utilizes the antenna quality factor, where it is a modification of the original Q factor method, amended by the loss Q factor of the antenna instead of the radiation Q factor. The method is verified for two kinds of antennas: the first is designed to operate at 868 MHz having a series resonance input impedance, and a second at 433 MHz having a parallel resonance input impedance. The method shows very high accuracy and prevent errors that may occur when using the conventional Wheeler cap method if the stored energy is not treated explicitly, which is considering the same imaginary part of the input impedance or input admittance for series resonance or parallel resonance, respectively

A Wideband and Compact Circularly-Polarized Rectenna for Low Power Application

International audienceThis paper presents a wideband and compact circularly polarized rectenna composed by an Archimedean spiral antenna that covers the S and C frequency bands and a silicon Schottky diode. This rectenna (rectifier + antenna) is used for electromagnetic energy harvesting over a wide frequency band, in order to power autonomous wireless sensors used for satellite health monitoring. For low incident power densities (around 14 µW/cm²) the measured efficiency of at least 19% between 2GHz and 3.5GHz can be achieved using this rectenna. The efficiency may reach 37% at some frequencies in this wideband operating bandwidth

A new compact dually polarized direction finding antenna on the UHF band

International audienc

Dual Circularly Polarized Reflectarray withIndependent Control of Polarizations

International audienc