Institut d'Électronique et de Télécommunications de Rennes
UMR CNRS 6164

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Soutenance de thèse

Francesco SCATTONE soutient sa thèse intitulée :

Phased array antenna with significant reduction of active controls

La soutenance aura lieu le Mardi 15 Décembre 2015 à 10:20, Salle des thèses (bât 1)
Campus de Beaulieu, Université de Rennes 1.

Abstract :

The objective of this thesis is to exploit the leaky-wave phenomena to enhance the per- formance of classical aperture antennas for space applications. Here, we consider planar configurations where the leaky modes are excited between a ground plane and a par- tially reflective superstrate, made of impedance sheets or dielectric slabs. Arrangements of small apertures opening on the ground plane are used to feed the antennas under study. The superstrate-like leaky-wave structures are developed in array or phased ar- ray configurations. These solutions are considered of interest in terms of flexibility of the system for next generation satellite links.

In order to efficiently study planar leaky-wave arrays, we have developed an analysis tool based on a Green’s function spectral approach. The developed tool allows to precisely analyze the proposed structure by taking into account the impact of the mutual coupling among the elements on the radiation performance of the whole antenna. In addition, it can handle extremely large structures in terms of wavelengths with a small computa- tional effort with respect to commercial tools. This tool has been used during the thesis to efficiently analyze the main features associated to the leaky-wave phenomenon, such as the gain enhancement and pattern shaping, for the improvement of the performance of the classical array solutions.

In particular, the gain enhancement of leaky-based structures can pave the way to the reduction of the number of elements of the associated phased arrays. In a leaky-wave configuration each element of the array will radiate with a larger equivalent aperture allowing a larger spacing among elements without affecting the final gain of the whole structure. This aspect is particularly important in the case of phased arrays, where phase shifters and control cells are, typically, the most expensive components of the sys- tem. As extensively explained in the manuscript, antennas for user segment might find the highest benefit by using leaky-wave solutions. In fact, the constraints on bandwidth (1 - 3%) and periodicity (1 - 2 wavelengths) make the leaky-wave technology suitable to reach the high aperture efficiencies required for such applications.

Besides the gain enhancement, the leaky-wave technology can be effectively exploited to conveniently shape the radiation pattern by properly engineering the design parameters of the antenna. For superstrate-like structures, as those considered in this work, such parameters are the reflectivity of the partial reflecting screens and their spacing. This capability can be used in phased arrays to generate a convenient element pattern to minimize the scan losses and filter the grating lobes appearing in the visible space when dealing with periodicities larger than a wavelength. Therefore, a synthesis procedure for thinned leaky-wave arrays is presented in the manuscript, showing the benefits of the superstrate configuration. In particular, it is shown that it is possible to design thinned arrays with a number of elements reduced by a factor 4, if compared with bare configurations, working in a band of 7%. Also, a novel array configuration, the irregular superstrate array, is presented. The irregular superstrate allows the reduction of the side lobes of the antenna below −20 dB in the considered 2.5% band, using a uniform excitation. Such solution avoids the use of complicate feeding networks of classical so- lution. This last configuration clearly shows that the shaping capability of leaky-wave antennas is the most appealing feature to be used in phased array solutions.

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