Gerard Caille

Sunflower Array Antenna with Adjustable Density Taper

A deterministic procedure to design a nonperiodic planar array radiating a rotationally symmetric pencil beam pattern with an adjustable sidelobe level is proposed. The elements positions are derived by modifying the peculiar locations of the sunflower seeds in such a way that the corresponding spatial density fits a Taylor amplitude tapering law which guarantees the pattern requirements in terms of beamwidth and sidelobe level. Different configurations, based on a Voronoi cell spatial tessellation of the radiative aperture, are presented, having as a benchmark the requirements for a typical multibeam satellite antenna.

Demonstration model of an active SAR subpanel

SPOT-Radar is the project for an X-band synthetic aperture radar (SAR) reusing the ground segment of SPOT. The subpanel active antenna demonstrator has demonstrated that 768 patches, 100 T/R (transmit/receive) active modules, three power supplies, and six microstrip power dividers can be integrated on a very limited surface (0.57 /spl times/ 0.45 square meters), with a total mass of less than 8 kg. All equipment has been electrically and mechanically designed in connection with launch vibrations, and temperature variations during in-orbit transfer and safe mode.<<ETX>>

Flexible multi-beam active Array Antennas for high-rate communication from satellites

We sum-up the developments of Satellite Array Antennas at Alcatel Space in the last decade; from elegant breadboards (EBB) until flight models (FM), as answers to stringent requirements for next-generation TV-broadcast systems (providing also fast internet for people not benefiting from wired ADSL), for specific “internet-in-the-sky” systems, and for high-rate data transmission from satellites observing very precisely the Earth, sky and stars.

European R and D on planar and conformal array antennas

This paper presents some of the issues studied within the European research network Antenna Centre of Excellence (ACE), with an emphasis on the area of planar and conformal arrays.

Conception d’une antenne bibande à large bande pour la téléphonie mobile

RésuméLes antennes pour la prochaine génération de téléphonie mobile nécessitent un fonctionnement multibande mais de plus chaque bande doit être individuellement « large bande », ceci dans un encombrement le plus faible possible. Cet article présente une structure rayonnante répondant à ces critères. L’obtention de ces caractéristiques est menée à bien par l’utilisation, sur des éléments planaires repliés, de courts-circuits filaires, de courts-circuits plans et de fentes débouchantes. L’influence des différentes techniques utilisées est analysée, interprétée et optimisée afin de parvenir à un élément unique pouvant fonctionner selon la norme GSM900 actuelle ainsi qu ’en umts. Le diagramme de rayonnement obtenu est lui aussi adapté aux terminaux de communications mobiles.AbstractThe next mobile communication generation needs to be multi-band but also require a large bandwidth behaviour for each band, all this associated with dimensions as small as possible. The paper presents a radiating structure having these different properties. The realisation of this antenna is obtained using a folded planar metallic elements, ground wires and open quarter-wave slots. The influence of each technique and parameter is studied, analysed and optimised to obtain a single radiating dual-band / large bandwidth element, operating in GSM900, umts and also ism 2.4 communication standards. The radiation pattern of this antenna is suitable for mobile handset applications.

Feasibility of scatterometers with new geometrical concepts

Two new geometrical concepts of scatterometer were investigated in order to reduce the variation of incidence angle on the fore and aft beams. The first one has fore, aft and mid beams nearly parallel and directed across the satellite track. The second one has concentric fore and aft beams. A feasibility study was undertaken to estimate system performances and budget in C band. This study begins with the determination of radiometric resolution requirement from a wind retrieval simulation in order to take into account the variation of azimuth angle along the beams. Finally performances and interface budgets are compared with currently developed systems.

Developments in active antennas for spaceborne radars

ALCATEL ESPACE, Toulouse, France, is developing active antenna technology, and designing and manufacturing tiles for two civil radar projects. One is for SPOTRADAR, a CNES (French Space Agency) project, and consists of 1/64th (equals one tile) of a 100 MHz X-band radar active antenna. The tile consists of 96 one-Watt-T/R modules, 3 power supplies, one radiating panel, 2 corporate feeds (one for T/R, one for internal calibration), and one control unit. The development started in 1990 and will be completed by March 1994. The other one is for ASAR, an ESA (European Space Agency) project, and consists of 1/20th (equals one tile) of a 16 MHz C-band radar active antenna. The tile consists of 16 eight-Watt T/R modules, 4 power supplies, one radiating pane, 2 corporate feeds, and one control unit. The development started in September 1991 and will be completed by June 1993. All tiles are representative of flight hardware and will be tested under space environment. This paper describes: (1) missions and radars, (2) whole antenna characteristics and projected performances, and (3) on-going developments and available test data (T/R modules, radiating panels, ...).