Dès lors que des éléments rayonnants sont placés à proximité les uns des autres, comme c'est le cas au sein des antennes réseaux à balayage électronique, des interactions électromagnétiques parasites se créent entre eux. Ces couplages se manifestent par une perturbation des répartitions de courants des sources du réseau. Leur impact dépend fortement de l'angle de dépointage du réseau mais est généralement néfaste, car ils modifient les caractéristiques du rayonnement des sources. Les différents objectifs de compacité et les spécifications de performances radioélectriques visés pour les radars aéroportées peuvent conduire à des structures qui supportent et favorisent ces phénomènes de couplages parasites, sous la forme d’ondes d’espace et de surface. Ces derniers peuvent aller jusqu'à entrainer l'impossibilité pour l'antenne de rayonner dans certaines directions et à certaines fréquences d’utilisation : on parle de directions aveugles. Ce phénomène limite de manière considérable le volume de dépointage opérationnel d'un système radar. La maîtrise du couplage entre les éléments rayonnants est donc l'une des problématiques essentielles du développement et du dimensionnement d'une antenne réseau. La recherche qui traite de ce sujet n'en est plus à ses débuts (les premiers radars à balayage électronique sont exploités depuis les années 50) mais reste toujours en attente de solutions innovantes permettant de mieux comprendre et maîtriser ces phénomènes. Dans cette thèse, plusieurs méthodes permettant de minimiser les effets du couplage dans les réseaux à balayage électroniques ont été investiguées. Les travaux s'orientent notamment autour du défi de réduire les conséquences des directions aveugles sans modifier la maille initiale du réseau d'antenne (contrainte iso-maille). / When radiating elements are located close to one another, as it is the case in electronically phased array antennas, parasitic electromagnetic interferences occur between them. The impact of these coupling mechanisms depends to a large extent on the scanning angle of the array, but is usually harmful, since it alters the radiating properties and the active input impedance of the sources. The compactness objectives and radioelectric performances required for airborne radars can lead to structures that support and foster these parasitic couplings, in the form of surface or space waves. In some cases, mutual coupling can even result in the impossibility for the array to radiate in certain directions and at certain frequencies. This phenomenon, referred to as scan blindness, significantly reduces the operating scan volume of a radar system. In that respect, the control of coupling mechanisms between radiating elements is a major issue when developing an array antenna and although the research that deals with this subject is no longer in its infancy, it is always pending for new and innovating solutions to master these phenomena. In this thesis, different solutions enabling to minimize the effect of couplings in phased arrays are investigated. The presented research revolves around the challenge of limiting scan blindness consequences without modifying the initial mesh of the array antenna.

Mobile communication has become an essential part of our daily life. We love the flexibility of wireless cell phones and even accept their lower quality of service when compared to wired links. Similarly, we are looking forward to the day that we can continue watching our favorite TV programs while travelling anywhere and everywhere. Mobility, flexibility, and portability are the themes of the next generation communication. Motivated and fascinated by such technology breakthroughs, this effort is geared towards enhancing the quality of wireless services and bringing mobile satellite reception one step closer to the market. Meanwhile, phased array antennas are vital components for RADAR applications where the antenna is required to have certain scan capabilities. One of the main concerns in that perspective is how to avoid the potential of scan blindness in the required scan range. Targeting to achieve wide-band wide-scan angle phased arrays free from any scan blindness our efforts is also geared. Conventionally, the key to lower the profile of the antenna is to use planar structures. In that perspective microstrip patch antennas have drawn the attention of antenna engineers since the 1970s due to their attractive features of being low profile, compact size, light weight, and amenable to low-cost PCB fabrication processes. However, patch elements are basically resonating at a single frequency, typically have <2% bandwidth, which is a major deficit that impedes their usage in relatively wide-band applications. There are various approaches to enhance the patch antennas bandwidth including suspended substrates, multi-stack patches, and metalized cavities backing these patches. Metalized cavity-backed patch structures have been demonstrated to give the best performance, however, they are very expensive to manufacture. In this dissertation, we develop an alternative low-cost bandwidth enhancement topology. The proposed topology is based on substrate-integrated waveguides. The great potential of the proposed structure lies in being amenable to the conventional PCB fabrication. Moreover, substrate-integrated cavity-backed structures facilitate the design of sophisticated arrays that are very expensive to develop using the conventional metalized cavity-backed topology, which includes the common broadside arrays used in fixed-beam applications and the scanned phased arrays used in RADAR applications.