Cette thèse est consacrée à la conception et à la mise en œuvre d’un réseau d’antenne multifonction.  Basé sur le concept du Time Modulated Array (TMA), réseau modulé dans le temps et grâce à des switches cette étude montre la possibilité de réaliser un réseau multifonctions. Deux fonctions ont été étudiés, une fonction radar (fonction principale) et une fonction communication (fonction secondaire). Une des innovations apportées par ce principe est la bidirectionnalité (chaque fonction est réalisée dans une direction différente) et l’aspect simultané des fonctions exécutées. . La technique conventionnelle du TMA présente aussi des inconvénients pour être utiliser dans des applications radar.  En effet, les variations de directivité, l'angle d'ouverture ainsi qu’une grande sensibilité aux interférences font que le TMA n’est pas compatible avec des applications radar. En effet, une variation de directivité provoque une variation de puissances à l'émission donc les signaux réfléchis souffriront également de cette variation qui peut ainsi créer des erreurs de détections. Des variations de l'angle d'ouverture crée une variation de la résolution angulaire du radar dans le temps ce qui perturbe la capacité de discrimination du radar. De plus, le rejet des interférences est aussi nécessaire afin d'éviter d'être aveuglé par un brouilleur ou par les échos parasites pendant notre détection. Pour résoudre ces inconvénients une méthode spécifique appelée Adapted Radar TMA a ainsi été développée. Grâce à une méthode d'optimisation (algorithme génétique) avec des contraintes définis, avec comme variables principale la loi d’excitation des antennes, plusieurs compromis ont été proposés afin de mutualiser et maximiser les performances de chaque partie (radar et communication). Ainsi 3 méthodes de loi d'excitation des antennes (ou pondération) ont été pensés. Par le biais de ces méthodes, la directivité et l'angle d'ouverture ont été contrôlés. Le rejet des interférences est désormais possible dans une direction donné. De plus, le réseau multifonction est aussi capable de fournir une partie communication ajouté à la partie radar déjà existante. L'optimisation exploite le comportement instantané d'ARTMA. Ainsi, en utilisant la variation des lobes secondaires dus aux changements des poids dans le temps, plusieurs modulations peuvent être adressées, à savoir une modulation ASK ou QAM. Un prototype de ce réseau multifonction comportant 16 antennes a été conçu. Les résultats des mesures ont fourni de bons résultats et ont validé le concept d'une communication en utilisant une modulation d'amplitude et de phase en faisant varier les lobes secondaires dans le temps grâce à des switchs en amont des antennes. / This thesis is devoted to the design and implementation of a multifunctional antenna array. Based on the concept of Time Modulated Array (TMA), array modulated in time with switches this study shows the possibility of a multifunction array. Two functions were studied, a radar function (main function) and a communication function (secondary function). One of the innovations of this principle is the bidirectional (each function is performed in a different direction) and the simultaneous appearance of the functions performed. The conventional technique of TMA also has drawbacks to be used in radar applications. Indeed, variations of directivity, beamwidth and a sensitivity to interference make the TMA no compatible with radar applications. Indeed, a directivity variation causes variations in the power transmission therefore the reflected signals also suffer from these variations, which can thus create errors detections. Variations in the beamwidth creates a change in the angular resolution of the radar in time thereby interfering with the discrimination ability of the radar. In addition, the interference rejection is also needed to avoid being blinded by a jammer or clutter during our detection. To overcome these drawbacks a specific method called Adapted Radar TMA has been developed. Through an optimization method (genetic algorithm) with defined constraints using as main variable the excitation law of the antennas, several compromises were proposed in order to make matched and maximize the performance of each part (radar and communication). Thus methods 3 excitation law of the antennas (weighting coefficients) were thought. Through these methods, the directivity and the beamwidth have been controlled. The interference rejection is now possible in a given direction. In addition, the multifunction array is also capable of providing a communication part added to the existing part radar. Optimization operates with ARTMA instant behavior. Thus, using the variation of the sidelobes due to changes in weighting coefficients over the time, several modulations may be addressed, namely ASK or QAM. A prototype of this multifunction network with 16 antennas was designed. Measurement results have provided good results and have validated the concept of communication using an amplitude and phase modulation by varying the side lobes in time through the switches before of the antennas.

Dual-band antenna elements that support dual-polarization provide ideal performance for applications including space-based platforms, multifunction radar, wireless communications, and personal electronic devices. In many communications and radar applications, a dual-band, dual-polarization antenna array becomes a requirement in order to produce an electronically steerable, directional beam capable of supporting multiple functions. The multiple polarizations and frequency bands allow the array to generate multiple simultaneous beams to support true multifunction radar. Many of the applications in spaced-based systems and personal electronic devices have strict restraints on the size and weight of the antenna element, favoring a low-profile, lightweight device. The research performed in this dissertation focuses on the design of a dual-band, dual-polarized antenna element capable of operating as an isolated element or in an array environment. The element contains two concentric, dual-polarized radiators. The low band radiator is a shorted square ring antenna, and the high band radiator is a square ring slot. Each constituent element achieves circular polarization through the introduction of triangular perturbations into opposing corners of the radiating element. This technique has been shown to introduce two, near-degenerate modes in the structure that – when excited in phase quadrature – combine to form circular polarization. The perturbations allow circular polarized operation with only a single feed point. The sense of the circular polarization is determined by the location of the feed point with respect to the perturbations. Both senses of circular polarization are excited by the introduction of orthogonal feeds for each of the two radiating elements. Thus, dual-ban, dual-circular polarization is obtained. The element achieves a low-profile from its printed circuit board realization. The high band square ring slot is realized in stripline. The orthogonal feeding transmission lines are printed on opposing sides of an electrically thin dielectric layer to allow them to cross without physically intersecting. This thin feeding substrate is sandwiched between two dielectric layers of matched dielectric constant. A ground plane is located on the top and bottom of the sandwiched dielectric structure, and the top ground plane contains the square ring slot with perturbed corners. Slotted stripline structures have been shown in the literature to excite a parallel-plate mode that can degrade overall performance of the antenna. Plated through holes are introduced at the outer perimeter of the square ring slot to short out this parallel-plate mode. The plated through holes (also called vias) serve as the shorting mechanism for the low band microstrip shorted square ring radiator. This element also contains triangular perturbations at opposing corners to excite circular polarization with a single feed point. In this element, orthogonal probe feeds are present to excite both senses of circular polarization. A dual-band, dual-polarized antenna element was built, tested, and compared to simulations. The constructed element operated at two distinct industrial, scientific, and medical (ISM) frequency bands due to their popularity in low power communications. The antenna element was realized in a multilayer printed circuit layout. A complex design procedure was developed and submitted to a printed circuit board company who manufactured the antenna element. The s-parameters of the antenna were measured using a Network Analyzer, and the results show good agreement with simulations. The radiation and polarization characteristics were measured in a compact range facility. These results also agreed well with simulations. The measured results verify the simulation models that were used in the simulations and establish a confidence level in the feasibility of constructing this element. The dual-band, dual-polarization nature of this element was established through the construction and measurement of this element. A novel size reduction technique was developed that allows for significant reduction of the element's footprint. This size reduction facilitates the placement of this element within an array environment. The loading technique utilizes a structure analogous to a parallel-plate capacitor to drastically reduce the overall size of the low frequency shorted square ring. The loading structure uses a substrate that is separate from that of the radiating elements. This allows the load to use a high dielectric material to achieve a high capacitance without requiring the radiating elements to be printed on high dielectric material that is potentially expensive and lossy at microwave frequencies. The two frequency bands were selected to be in separate industrial, scientific, and medical (ISM) bands. These frequency bands are increasingly popular in low power communication devices because unlicensed operation is permitted. The 2.45 GHz and 5.8 GHz ISM bands are commonly used for applications including Bluetooth technology, multiple 801.11 protocol, cellular phone technology, and cordless phones. The ISM bands were chosen for this antenna element due to their popularity, but this antenna is not restricted to these bands. The frequency ratio can be altered by controlling the dielectric constant used in the printed circuit board design, the parameters of the capacitive loading structure, and the size of the constituent elements that are used. After the size reduction technique is applied, the dual-band, dual-polarized elements can be placed in an array environment resulting in an array capable of generating both senses of circular polarization in the two, distinct ISM bands. This provides an aperture capable of supporting multiple functions. Depending on the applications required, the frequency bands of the antenna element can be altered to suit the particular system needs. The array analysis performed in this dissertation used a unique hybrid calculation technique that utilizes nine active element patterns to represent the patterns of the individual elements within a large antenna array. A common first look at array performance is achieved by multiplying the element pattern of an isolated element by an array factor containing the contributions of the geometrical arrangement of the antenna elements. This technique neglects mutual coupling between elements in the array that can alter the impedance match and radiation characteristics of the elements in the array. The active element pattern defines the radiation pattern of a given element in an array when all other elements are terminated in a matched impedance load. The active element pattern is unique for each element in an array. When these patterns are summed, the exact array pattern is obtained. While this technique has the advantage of accuracy, it is not ideal because it requires the simulation, calculation, or measurement of the pattern for each element in the array environment. The technique developed in this dissertation uses only nine active element patterns. These elements are then assigned to represent the active element patterns for all elements in the array depending on the geometrical region where the given element resides. This technique provides a compromise between the speed of using a single element pattern and the accuracy of using the unique active element pattern for each element in the array. The application of these two concentric, coplanar radiators along with the capacitive loading technique provides a unique contribution to the field of antenna engineering. The majority of dual-band antenna elements in the literature operate with a single polarization in each band. The ones that operate with dual-polarization in each band are typically limited to dual-linear polarization. Circular polarization is preferable to linear in many applications because it allows flexible orientation between the transmitting antenna and receiving antenna in a communications system, while also mitigating multipath effects that lead to signal fading. The ability to operate with two, orthogonal senses of circular polarization allows a system to reuse frequencies and double system capacity without requiring additional bandwidth. The uniqueness of this element lies in its ability to provide dual-circular polarization in two separate frequency bands for an individual element or an antenna array environment. The arrangement of the two element geometries with the addition of the novel capacitive loading technique is also unique. The performance of this element is achieved while maintaining the light weight, low profile design that is critical for many wireless communications applications. This dissertation provides a detailed description of the operation of this dual-band, dual-polarized antenna element. The design of the constituent elements is discussed for several polarization configurations to establish an understanding of the building blocks for this element. The dual-band, dual-polarized element is presented in detail to show the impedance match, isolation, and axial ratio performance. The capacitive loading technique is applied to the dual-band, dual-polarized element, and the performance with the loading in place is compared to the performance of the unloaded element. Next, there is an in-depth description of the array calculation technique that was developed to incorporate mutual coupling effects into the array calculations. This technique is then applied to the dual-band, dual-polarized array to show the performance of several array sizes. / Ph. D.