Several novel designs of printed monopole antennas are proposed and experimentally studied. These antennas have the advantages of low profile, light weight and easy construction and can be printed on dielectric substrates and integrated with associated circuitry on the same substrates, which not only reduces the manufacturing cost but also decreases the required size of the complete system. This dissertation mainly consists of four sections and several novel designs are introduced in each section. First, a novel dual-band antenna with two stacked inverted-F strips and a CPW-fed folded inverted-F strip antenna are proposed. Second, a novel printed dual-band double-T monopole antenna, comprising two stacked T-shaped monopoles, is discussed. Third, three diversity antenna designs obtained by protruding a ground plane with optimal dimensions between two printed monopoles for WLAN communication applications in the 2.4 GHz and 5.2 GHz bands are presented. Good dual-polarized radiation with an enhanced port decoupling (isolation less than ¡V27 dB) for the two feeding ports is obtained. Finally, a novel printed ultra-wideband diversity monopole antenna is shown. The operating bandwidth of the ultra-wideband antenna reaches about 5.4 GHz, covering the WLAN bands at 2.4, 5.2 and 5.8 GHz, and the antenna can provide spatial diversity to combat the multipath fading problem.

In this thesis, two novel antennas and three advanced design concepts for further studies are presented. Firstly, the design of diversity dual-band inverted-F monopole antenna using two back-to-back stacked metallic strips for operating in the 2.4 and 5.2 GHz WLAN band is presented. Secondly, the diversity dual-band inverted-F monopole antenna mounted vertically at the edge of a system circuit board is studied. Finally, three advanced design concepts are discussed to demonstrate the methods of controlling radiation patterns to achieve better radiation characteristics of the antenna.

Novel printed monopole antennas, including diversity antennas, monopole array antennas and broadband antennas for WLAN operation, are experimentally studied and presented in this dissertation. These proposed antennas can be printed on dielectric substrates and practically integrated with system circuit boards by using printed circuit board technique. Also, the proposed antennas are low cost in fabrication and the reliability of system circuit boards can be improved. First, the design of the diversity antenna, which mainly comprises two substantially orthogonal printed monopoles and are placed symmetrically with respect to a protruded ground plane of T shape, shows good isolation between the two feeding ports of the proposed antenna. Second, the design of the printed array antenna, which comprises three equally-spaced equilateral-triangular monopoles, is proposed. Among the three monopoles, the center one has a larger size, which mainly controls the lower operation band, and the other two monopoles have a smaller size for higher operation band and show higher antenna gain and wider operating bandwidth. Finally, the quasi-self-complementary antenna is introduced. With compact size and wide bandwidth achieved, the proposed antenna is suitable for a mobile communication device, and can also provide good spatial diversity to combat the multi-path interference problem when mounting two proposed antennas appropriately spaced on a WLAN card.

No / This study presents a miniaturised multiple input and multiple output /diversity antenna which is suitable for high data-rate communication systems such as mobile ultra-wideband (UWB). This antenna assembly comprises two identical planar inverted-F antennas, a T-shaped structure connecting them and a finite ground plane. The T-shaped structure improves the impedance matching and suppresses the mutual coupling between the antenna elements over a wider bandwidth than previously reported. The compact envelope dimension of this antenna is 50 x 90 x 7.5 mm(3). Theoretical and experimental S-parameters are illustrated for this antenna that fully cover the UWB operating frequency band of 3.1-10.6 GHz, with a reflection coefficient and mutual coupling better than -10 and -20 dB, respectively. Acceptable agreement is obtained between computed and measured radiation patterns, gains, envelope correlation coefficient and channel capacity loss. The proposed antenna is an attractive candidate to provide pattern diversity and enhance channel capacity in a rich scattering environment.

L’Internet-of-Things désigne un développement en plein essor d’objets interconnectés et qui sont susceptibles de modifier nombre de services au sein de l’industrie comme pour la personne. Les développements actuels buttent sur plusieurs verrous dont celui de l’autonomie énergétique des objets ou encore des procédés de fabrication économiquement acceptables et respectueux de la planète. Dans ce contexte, la récupération d'énergie est une thématique largement répandue faisant appel à des sources très variées (mécanique, thermique, électromagnétique...). Cette thèse est notamment orientée vers la récupération d'énergie électromagnétique ambiante. Le second point caractéristique de cette thèse est de s'intéresser à des substrats souples et si possible recyclables. Le défi consiste à récupérer l’énergie provenant d’un champ électromagnétique ambiant extrêmement faible : ceci concerne l’antenne, qui doit par ailleurs répondre à une exigence de flexibilité pour son intégration future à un objet souple et déformable, et l’électronique de traitement de l’énergie.Le travail de thèse est articulé autour de trois phases principales :Dans la première phase, il s’agissait de l’étude des structures d’antennes compatibles en fréquence et en puissance reçue avec l’application de récupération d’énergie et une réalisation physique sur base souple (papier, tissu...). Cette phase a permis de présenter les différentes approches pour combiner les sources RF.Dans la deuxième phase, il s’agit de l’étude sur le rôle de circuits redresseurs dans le système de récupérer d’énergie. Les méthodes d'extraction des paramètres sont discutées en dissociant chaque élément et leurs rôles. De nombreuses mesures ont été réalisées afin de comparer différents modèles de la diode utilisée pour le redressement, en tenant compte également de l'impact réel du processus de fabrication et du processus de mesure.Une troisième phase permet l’optimisation de l’ensemble antenne et électronique (rectenna) pour divers scenarii et le suivi de la variabilité pour maintenir les pertes du système a minima. La réalisation de démonstrateurs pertinents, testés et caractérisés est présentée. / Internet-of-Things means a growing development of interconnected objects that are likely to change many services within the industry as well as for the individual. Several barriers, including the energy autonomy of objects or production processes that are economically acceptable and respectful of the planet, hamper current developments. In this context, energy recovery is a widespread theme using a wide range of sources (mechanical, thermal, electromagnetic, etc.). This thesis is oriented towards the recovery of ambient electromagnetic energy. The second characteristic point of this thesis is to focus on flexible and, if possible, recyclable substrates. The challenge is to recover energy from an extremely low ambient electromagnetic field: this concerns the antenna, which must also meet a requirement for flexibility for its future integration with a flexible and deformable object, and the electronics of energy processing.The work of this thesis conducted in three phases.In the first phase, it was the study of the antenna structures compatible with frequency and power received with the energy harvesting application and a physical realization on flexible base (paper, textile, etc.). This phase allowed presenting the different approaches to combining the RF sources.In the second phase, the study on the role of rectifying circuit in the system of recovering wireless energy was presented. Methods for extracting parameters were discussed by separating each element and its roles. Numerous measurements have been conducted to compare different models of the diode, taking into account also the actual impact of the manufacturing process and the measurement process.A third phase allows the optimization of the antenna and electronic assembly (rectenna) for various scenarios and the monitoring of variability to keep the losses of the system at minima. The production of relevant demonstrators, test and characterization were presented.

The objectives of this work were to investigate, design and implement Multiple-Input Multiple-Output (MIMO) antenna arrays for mobile phones. Several MIMO antennas were developed and tested over various wireless-communication frequency bands. The radiation performance and channel capacity of these antennas were computed and measured: the results are discussed in the context of the frequency bands of interest. A comprehensive study of MIMO antenna configurations such as 2 × 1, 3 × 1, 2 × 2 and 3 × 3, using polarisation diversity as proposed for future mobile handsets, is presented. The channel capacity is investigated and discussed, as applying to Rayleigh fading channels with different power spectrum distributions with respect to azimuth and zenith angles. The channel capacity of 2 × 2 and 3 × 3 MIMO systems using spatial polarisation diversity is presented for different antenna designs. The presented results show that the maximum channel capacity for an antenna contained within a small volume can be reached with careful selection of the orthogonal spatial fields. The results are also compared against planar array MIMO antenna systems, in which the antenna size considered was much larger. A 50% antenna size reduction method is explored by applying magnetic wall concept on the symmetry reference of the antenna structure. Using this method, a triple dual-band inverted-F antenna system is presented and considered for MIMO application. Means of achieving minimum coupling between the three antennas are investigated over the 2.45 GHz and 5.2 GHz bands. A new 2 2 MIMO dual-band balanced antenna handset, intended to minimise the coupling with the handset and human body was proposed, developed and tested. The antenna coupling with the handset and human hand is reported in terms the radiation performance and the available channel capacity. In addition, a dual-polarisation dipole antenna is proposed, intended for use as one of three collocated orthogonal antennas in a polarisation-diversity MIMO communication system. The antenna actually consists of two overlaid electric and magnetic dipoles, such that their radiation patterns are nominally identical but they are cross-polarised and hence only interact minimally.