Dépointage | EPFL Graph Search

Le dépointage d'une antenne est la déviation angulaire du faisceau électromagnétique émis par cette antenne, sous l'effet d'une perturbation (vent, choc, séisme, déformation d'un élément, surcharge quelconque). Description du phénomène Le terme dépointage provient du jargon professionnel des télécommunications sans fil. Ce terme s'oppose au pointage d'une antenne, qui désigne le fait que celle-ci vise une autre antenne, distante de quelques dizaines de kilomètres (relais de télécommunication terrestre), ou plusieurs centaines de kilomètres (satellite de communication) avec laquelle elle communique. Lors de leur installation sur un pylône ou sur un mât, les antennes sont orientées de manière très précise vers d'autres antennes. L'orientation se fait mécaniquement, en visant l'antenne distante et en réglant le tilt manuellement, ou en commandant de manière électronique l'inclinaison du faisceau, grâce à un système intégré à l'antenne. Les agents extérieurs (vent, séisme, éc

Design of novel radiating elements for SATCOM phased arrays in Ku-Band

Baptiste Fernand Hornecker

The present thesis deals with the design of a planar antenna array for the communication between a civil aircraft (Dassault's Falcon) and an Inmarsat satellite. The final goal is to provide high speed Internet access in X/Ku-Band (8-12GHz / 12-18GHz), and possibly even in K/Ka- Band (18-27GHz / 17-40GHz). The study starts with the Ku-Band only, then evolves towards the transmission band and finishes with their Ka-Band counterparts. The main constraint of the thesis is that the final result should be a low profile antenna that will be easy to integrate below the fuselage of an aircraft. At the same time, the antenna has to provide a beam steering mechanism in order to track the position of the targetted satellite while the aircraft is moving. The usual way to achieve it is to implement some dedicated electronic chips below each radiating element of array. Dassault Aviation has its own alternate and more mechanical oriented solutions. Since the communication system is intended for top-notch business jets produced in small series, cost is not here a decisive criterion. This thesis assumes the existence of the beam-steering system and concentrates on a proof of concept and careful design of the antenna elements that will constitute the final array. They have to satisfy tight constraints in terms of size, return loss, mutual coupling with neighbors, efficiency, radiation pattern and dual circular polarization quality. Printed multilayer antennas have been retained as the best candidates, and themain parts of the thesis have been dedicated to their study. The thesis concludes with the presentation of an apparently completely unrelated and independant topic, namely the simulation of nanoscale 2D planar structures based on Graphene. The rationale for this last chapter is to provide a prospective study of the use of Graphene to create a variable capacitance. This component is always needed in the beamforming network of reconfigurable and scanning arrays. Our laboratory is developing a deep knowledge of the electromagnetic properties of Graphene-based devices and these varicaps could lead to very interesting applications in high frequencies, once the Graphene technology has definitely progressed. Thanks to electrostatics Green's functions, a variable capacitor based on Graphene has been simulated, and a Quantumeffect -the Quantum capacitance of Graphene- has been successfully tackled from a numerical point of view.

EPFL2016

Dual frequency reflectarray cell using split-ring elements with RF MEMS switches

Caner Güçlü, Julien Perruisseau-Carrier

In this study, a dual frequency circularly polarized reconfigurable reflectarray (RA) cell with RF-MEMS switches is designed. RA combines the advantages of reflector-based and phased array antennas, providing a low-cost and high performance antenna array solution. In their reconfigurable implementations, RAs are capable of electronic beam scanning/forming with potential multiband operation, as discussed here. In this work, reconfigurability is achieved by series RF-MEMS switches that are placed on the ring strips. Switches are used to change the orientation of the gaps to realize the rotation of the element. The RA antenna composed of these elements will be capable of beamsteering independently for the two operating frequencies. In the following section the RA unit cell geometry is presented, some simulation results are given, and the phase design curve is discussed.

IEEE Service Center, 445 Hoes Lane, Po Box 1331, Piscataway, NJ 08855-1331 USA2010

Antennas for low-cost Ka-band ground terminal devices

Joana Rita Alves dos Santos Silva

The ever-growing demand for high-speed data links together with the increasing congestion in the traditional microwave spectrum are pushing for the exploitation of higher microwave and millimeter-wave (mm-wave) frequencies, including the so-called Ka band. Major investments came along, especially in the satellite communications industry, raising the technological con-straints imposed on electronic equipment, mainly concerning performance, compactness and both reduced cost and weight. The great antenna size reduction achieved at Ka band has boosted the research towards satel-lite-on-the-move applications (SOTM), aiming the development of ground terminal antennas for both commercial and personal use. Such antennas must work simultaneously at downlink and uplink Ka bands with circular polarization and also have beam steering capabilities to keep a steady connection with the satellite. In addition, the target is also achieving a cost-effective low-profile antenna. The present thesis is focused on the design of feed antennas to be integrated in mechanical beam steering systems for the aforementioned application. Three different designs are here proposed and discussed. The first one, a wideband ridged horn antenna, was tested standalone and with a dielectric lens antenna. Once good results were achieved in both sce-narios, reducing its height would be the next goal. Thus, the second design is a cavity backed patch antenna. A comparison between both feed antennas is performed, highlighting the pros and cons of both solutions, either standalone or with the same dielectric lens antenna. Here, the first studies with a planar lens antenna are shown. Finally, the third device consists of a ridged cavity antenna with a cross-slot on its top aperture. This time, the feed was successful-ly tested with a transmitarray which allows achieving a more compact antenna system than the first one here presented. This thesis also analyzes two different manufacturing techniques, traditional milling technique and an innovative additive manufacturing (AM) technique based on metallized polymers called stereolithography (SLA). The present AM-SLA prototypes clearly illustrate the strong potential of this technology and pushes for its further assessment.

EPFL2017