In recent years, multi-functional reconfigurable antennas (MRA) has attracted much attention in wireless communication. The reconfigurable antenna can adapt itself with changing system conditions, and it can provide different multi-functionalities which can give better system performances. Instead of using multiple antennas, a single reconfigurable antenna can provide the same performance and occupy less space. By using the parasitic layer technique, an antenna can be turned into a reconfigurable antenna. The main objective of this thesis is to study radiation pattern reconfiguration of the horn antenna by using the parasitic layer concept. The MRA consists of a single horn, dielectric loaded truncated pyramid (DLTP), and the parasitic layer. The antenna that is chosen in this thesis is the horn antenna because it provides high directivity. DLTP is used for magnification purpose. The results show that three modes of operations that provide better performances compared to the single horn antenna are achieved.

Cette thèse est consacrée à la mise en place d'un système hyperfréquence dédié à l'imagerie du proche sous-sol. L'analyse de l'onde mesurée après interaction de l'onde incidente avec le milieu permet de remonter aux propriétés électromagnétiques de la structure illuminée. Ici, nous choisissons d'utiliser une seule fréquence en s'appuyant sur une configuration multistatique pour garantir une meilleure diversité de l'information.L'imagerie quantitative exige un calibrage minutieux des données mesurées après correction des erreurs expérimentales. Un calibrage a été donc proposé, basé sur la mesure du diagramme de rayonnement de chaque antenne. Celles-ci sont modélisées quantitativement en champ proche grâce à une combinaison de fils sources adéquatement optimisée. Ce calibrage, rapide et simple, ne nécessite pas d'objets de calibrage supplémentaires. Il a été d'abord testé dans le cas de la diffraction par des objets 2D en espace libre, puis dans le cas d'objets faiblement enfouis. Les champs calibrés servent de données d'entrée à des algorithmes d'inversion. En terme de localisation, les résultats obtenus sont très satisfaisants. Quant à la caractérisation, la configuration stratifiée apparaît bien moins propice que la configuration en espace libre, de part la faible quantité d'information disponible. Des changements ont été apportés à la configuration (différentes antennes avec ou sans orientation) dans l'optique d'améliorer le rapport signal à bruit. Bien que les reconstructions des permittivité soient encore perfectibles, les premiers résultats sont intéressants d'autant plus que les algorithmes n'exploitent aucune information a-priori sur la cible. / This thesis is devoted to the development of a microwave system dedicated to subsurface imaging applications. The analysis of the measured wave after the interaction with the medium allows to retrieve the electromagnetic properties of the probed structure. Here, we choose a single frequency operating mode combined with a multistatic configuration in order to improve the information diversity.Quantitative imaging requires a high-precision calibration of the measured data even after a careful correction of experimental errors. Thus, a calibration method is proposed, exploiting the measurement in free-space of the radiation pattern of each antenna. These patterns are quantitatively modeled thanks to an optimized linear combination of elementary sources positioned on the antenna's aperture. This simple and efficient calibration avoids additional measurements with calibration objects. This method provides successful results in a 2D free space scattering problem, as well as in the shallowly buried targets case.The calibrated data serve as inputs to inversion algorithms. As localization is concerned, very satisfactory detection results are obtained. Regarding the characterization aspects, the results indicate that the stratified configuration is less suitable than the free space configuration, due to its lack of spatial information. In order to improve the signal-to-noise ratio, some amendments are made to the experimental configuration (different antennas with or without orientation). Although the permittivity reconstructions are perfectible, the first results are promising especially since no a-priori on the targets has been inserted in the inversion algorithm so far.

La chambre réverbérante à brassage de modes (CRBM) est une cavité métallique fermée surdimensionnée, équipée d’un brasseur de modes. Le brassage de modes rend le champ électromagnétique homogène et isotrope à l’intérieur de la CRBM (dans son volume utile). Cette thèse illustre tout d’abord une nouvelle méthode pour évaluer les performances d’un brasseur de modes (via le spectre Doppler). Ensuite, elle présente une nouvelle méthode permettant de mesurer la surface équivalente radar (SER) d’un objet canonique en utilisant la technique de fenêtrage temporel ou time-gating. Enfin, elle présente une nouvelle méthode permettant de mesurer le diagramme de rayonnement d’une antenne dans une cavité surdimensionnée via la technique de time-gating. / The reverberation chamber (RC) is an oversized closed metal cavity, equipped with a mode-stirrer. The mode stirring makes the electromagnetic field homogeneous and isotropic inside the RC (in its useful volume). This thesis illustrates firstly a new method for evaluating the performance of a mode-stirrer (via the Doppler spectrum). Then, it presents a new method for measuring the radar cross section (RCS) of a canonical object using the time-gating technique. Finally, it presents a new method for measuring the antenna radiation pattern in an oversized cavity via the time-gating technique.

Dielectric resonator antenna (DRA) technologies are applicable to a wide variety of mobile wireless communication systems. The principal energy loss mechanism for this type of antenna is the dielectric loss, and then using modern ceramic materials, this may be very low. These antennas are typically of small size, with a high radiation efficiency, often above 95%; they deliver wide bandwidths, and possess a high power handling capability. The principal objectives of this thesis are to investigate and design DRA for low profile personal and nomadic communications applications for a wide variety of spectrum requirements: including DCS, PCS, UMTS, WLAN, UWB applications. X-band and part of Ku band applications are also considered. General and specific techniques for bandwidth expansion, diversity performance and balanced operation have been investigated through detailed simulation models, and physical prototyping. The first major design to be realized is a new broadband DRA operating from 1.15GHz to 6GHz, which has the potential to cover most of the existing mobile service bands. This antenna design employs a printed crescent shaped monopole, and a defected cylindrical DRA. The broad impedance bandwidth of this antenna is achieved by loading the crescent shaped radiator of the monopole with a ceramic material with a permittivity of 81. The antenna volume is 57.0  37.5  5.8 mm3, which in conjunction with the general performance parameters makes this antenna a potential candidate for mobile handset applications. The next class of antenna to be discussed is a novel offset slot-fed broadband DRA assembly. The optimised structure consists of two asymmetrically located cylindrical DRA, with a rectangular slot feed mechanism. Initially, designed for the frequency range from 9GHz to 12GHz, it was found that further spectral improvements were possible, leading to coverage from 8.5GHz to 17GHz. Finally, a new low cost dual-segmented S-slot coupled dielectric resonator antenna design is proposed for wideband applications in the X-band region, covering 7.66GHz to 11.2GHz bandwidth. The effective antenna volume is 30.0 x 25.0 x 0.8 mm3. The DR segments may be located on the same side, or on opposite sides, of the substrate. The end of these configurations results in an improved diversity performance.

Lors de cette thèse, on a développé un banc automatisé de relevé du diagramme de rayonnement particulièrement pour des antennes millimétriques avec faible directivité. On propose trois méthodes d’alimentation. La première méthode développée a été de concevoir une nouvelle sonde ayant un accès micro-coaxial de plus de 5cm afin de réduire la zone de masquage au minimum. Associée à une configuration de type flip-chip inversée, cette méthode a permis d’avoir une réduction de la zone de masquage de 80° à 20°. La deuxième méthode a été de concevoir une liaison souple par film souple de Kapton. Cette méthode présente l’avantage de placer une plus grande partie des connexions métalliques sous un plan de masse, mais nécessite une connexion optimale à la puce. Les résultats obtenus présentent une zone de masquage pratiquement inexistante, et sont conformes à l’état de l’art. La troisième méthode SER est basée sur la mesure de l’antenne sans placer de sondes ou de connecteurs spéciaux, mais en utilisant un système à charges connues. La simulation nous montre qu'il nous manque une dynamique par ces trois charges. / In this thesis, we designed and built a new 3D test bench, particularly for low-directivity integrated antennas at millimeter-wave frequencies. We proposed three feeding techniques for the antenna under test (AUT): a probe-fed technique, a flexible-transmission-line-fed technique and a radar-cross-section (RCS) method. The probe-fed method was developed with a customized probe, which involves an elongated (50 mm) coaxial line between the probe tip and the probe body, wherein the probe body is reversed (relative to the conventional measurement configuration) so it lies below the plane of the AUT. This method reduces the range of angles that are masked from 80° (for a conventional probe setup) to 20°. The second method was developed using a flexible transmission line with a modified flip-chip connection to the AUT. This method completely eliminates the masked zone. The third method characterizes the radiation pattern using a radar cross-section (RCS) method. This method requires neither a probe system nor connectors. However the simulation results demonstrate that there is insufficient variation in the ratio of received power to incident power as the load on the AUT is varied in order to make precise measurement with conventional measurement equipment.

There is currently a demand of mm‑wave on‑chip antennas to enable all kinds of new applications in several different areas. But the development requires, among other things, special equipment used during the measurement phase due to the small dimensions and the high frequencies. In this project a robotic measurement system, SAX (Single Arm eXtra), was designed and constructed at Micro and Nanosystems (MST) department at KTH Royal Institute of Technology (Sweden). The purpose of the SAX is to enable radiation pattern measurements of on‑chip antennas ( 140 GHz to 325 GHz ), whether the boresight is vertical or horizontal along with other requirements, by moving a converter with the measurement antenna around the antenna in question. Several alternative designs for the basic construction, both from other works and invented by the author, were analyzed based on the requirements for this project and other limitations. The chosen unique design, the SAX, is very compact and uses only one stepper motor. Several parts have been developed in this project to ensure the proper functionality of the SAX. That includes a main operator program, a motor input signal generating program, a motor input signal executing system, a security system, and a system for controlled rotation of the SAX. For the input signal to the motor two different algorithms to generate the time delays were developed and tested. They were adapted to make the motor manage the sweeps of an ever‑changing load with high inertia during acceleration and deceleration. One of them was developed to make the time delay array generation much more efficient albeit with larger approximation error. The SAX worked well and should be rather easy‑to‑use regarding the operation of the system, from the physical maneuvering to utilizing the sub‑systems to the running of the main operator program. It fulfilled the specific requirements by enable a cross pattern measurement from  -60° to +60°  both from above and from the side, adjustment of the radius between 15cm to 45cm , adjustment 10cm in height, to be rotated along the floor in steps of 1°, measurement steps of 1° with an accuracy of less than 0,5° (the largest error was measured to be ≤ 0,461°). However, some calibration work needs to be done before the optimal performance of the system is reached. As a verification of the operation of the system data from measurements of open‑ended waveguides was presented. / Det finns en efterfrågan på chipantenner för millimetervågor eftersom de kan möjliggöra allehanda produkter inom flera olika områden. Forskningen på dessa ställer dock bl.a. speciella krav på utrustning som används under testmätningsfasen p.g.a. de små dimensionerna och den höga frekvensen. I detta projekt har ett robotsystem, SAX (Single Arm eXtra), utformats och konstruerats på avdelningen för Mikro- och nanosystem på KTH. Syftet med SAX är att mäta högfrekventa chipantenner ( 140 GHz till 325 GHz ) genom att förflytta en frekvensomvandlare med tillhörande mätantenn i en cirkulär bana runt antennen ifråga, oavsett om den är riktad vertikalt eller horisontellt och givet andra kravspecifikationer. Flera designalternativ för den grundläggande konstruktionen, både från andras arbeten och framtagna av författaren själv, har analyserats utifrån kravspecifikation för detta projekt och andra begränsningar. Den valda unika designen, SAX, är väldigt kompakt och använder sig bara av en stegmotor. För att möjliggöra funktionen i den slutgiltiga produkten har flera delar tagits fram vilka inkluderar ett operatörsprogram, ett program för genererandet av motorstyrsignaler, ett program för motorstyrning, ett säkerhetssystem och ett rotationssystem för kontrollerad rotation av SAX. För genererandet av motorstyrsignaler i form av tidsfördröjda pulser framtogs två olika algoritmer. De ger anpassade accelerations- och retardationssignaler för att motorn ska klara av att förflytta en föränderlig last med stor tröghet. En av dessa framtogs med syfte att mycket effektivt generera pulstiderna om än med större approximationsfel. SAX fungerade tillfredsställande och torde vara ganska lättanvänd med tanke på vad systemet kräver av operatören, från att fysiskt manövrera systemet till att använda delsystemen till att använda operatörsprogrammet. Systemet uppfyllde de givna specifika kraven genom att möjliggöra mätningar i form av ett kryssmönster från -60° till +60°  både ovanifrån och från sidan, radiejustering från 15cm till 45cm , höjdjustering över 10cm , rotation över golvet i steg om 1° , mätningar i steg om 1° med en noggrannhet på 0,5° (den största avvikelsen uppmättes till ≤ 0,461°). Vidare kalibrering behöver dock utföras för att utnyttja den fulla potentialen hos konstruktionen. För att verifiera funktionsdugligheten för systemet presenterades data från mätningar gjorda på öppna vågledare.

Dielectric resonator antenna (DRA) technologies are applicable to a wide variety of mobile wireless communication systems. The principal energy loss mechanism for this type of antenna is the dielectric loss, and then using modern ceramic materials, this may be very low. These antennas are typically of small size, with a high radiation efficiency, often above 95%; they deliver wide bandwidths, and possess a high power handling capability. The principal objectives of this thesis are to investigate and design DRA for low profile personal and nomadic communications applications for a wide variety of spectrum requirements: including DCS, PCS, UMTS, WLAN, UWB applications. X-band and part of Ku band applications are also considered. General and specific techniques for bandwidth expansion, diversity performance and balanced operation have been investigated through detailed simulation models, and physical prototyping. The first major design to be realized is a new broadband DRA operating from 1.15GHz to 6GHz, which has the potential to cover most of the existing mobile service bands. This antenna design employs a printed crescent shaped monopole, and a defected cylindrical DRA. The broad impedance bandwidth of this antenna is achieved by loading the crescent shaped radiator of the monopole with a ceramic material with a permittivity of 81. The antenna volume is 57.0  37.5  5.8 mm3, which in conjunction with the general performance parameters makes this antenna a potential candidate for mobile handset applications. The next class of antenna to be discussed is a novel offset slot-fed broadband DRA assembly. The optimised structure consists of two asymmetrically located cylindrical DRA, with a rectangular slot feed mechanism. Initially, designed for the frequency range from 9GHz to 12GHz, it was found that further spectral improvements were possible, leading to coverage from 8.5GHz to 17GHz. Finally, a new low cost dual-segmented S-slot coupled dielectric resonator antenna design is proposed for wideband applications in the X-band region, covering 7.66GHz to 11.2GHz bandwidth. The effective antenna volume is 30.0 x 25.0 x 0.8 mm3. The DR segments may be located on the same side, or on opposite sides, of the substrate. The end of these configurations results in an improved diversity performance. / General Secretariat of Education and Scientific Research Libya

No / A miniaturized conical helix antenna is presented, which displays vertical polarization with electrically small dimensions of 10mm×10mm×45mm. The resonance of the antenna is made tunable by adding a variable digital MEMS capacitor load at the bottom of the helix, giving a tuning range of 316 MHz to 400 MHz. The antenna demonstrates considerable impedance matching bandwidth and gain over the entire tuning frequency band. Most importantly, the antenna is capable of compact, flexible and easy integration into a wireless device package or for platform installation. / Datong of Seven Technology Group, for their support under the KTP project grant No. 008734.

This thesis describes an electrically thin surface used for electromagnetic applications in the microwave regime. The surface is free-standing and its primary purpose is to modify the phase distribution, or the phase and amplitude distribution of electromagnetic fields propagating through it: it is called phase shifting surface (PSS) in the first case, and phase and amplitude shifting surface (PASS) in the second case. For practical applications, the surface typically comprises three or four layers of metallic patterns spaced by dielectric layers. The patterns of the metallic layers are designed to locally alter the phase (and amplitude in the case of the PASS) of an incoming wave to a prescribed set of desired values for the outgoing wave. The PSS/PASS takes advantage of the reactive coupling by closely spacing of the metallic layers, which results in a larger phase shift range while keeping the structure significantly thin. The PSS concept is used to design components such as gratings and lens antennas which are presented in this document. The components are designed for an operating frequency of 30 GHz. The PSS phase grating gives high diffraction efficiency, even higher than a dielectric phase grating. Several types of lens antennas are also presented, which show comparable performance to that of a conventional dielectric plano-hyperbolic lens antenna with similar parameters. The PASS concept is used in a beam shaping application in which a flat-topped beam antenna is designed. This work demonstrates the potential for realising thin, lightweight and low-cost antennas at Ka band, in particular for substituting higher-gain antenna technologies such as conventional dielectric shaped lens antennas.

This thesis describes an electrically thin surface used for electromagnetic applications in the microwave regime. The surface is free-standing and its primary purpose is to modify the phase distribution, or the phase and amplitude distribution of electromagnetic fields propagating through it: it is called phase shifting surface (PSS) in the first case, and phase and amplitude shifting surface (PASS) in the second case. For practical applications, the surface typically comprises three or four layers of metallic patterns spaced by dielectric layers. The patterns of the metallic layers are designed to locally alter the phase (and amplitude in the case of the PASS) of an incoming wave to a prescribed set of desired values for the outgoing wave. The PSS/PASS takes advantage of the reactive coupling by closely spacing of the metallic layers, which results in a larger phase shift range while keeping the structure significantly thin. The PSS concept is used to design components such as gratings and lens antennas which are presented in this document. The components are designed for an operating frequency of 30 GHz. The PSS phase grating gives high diffraction efficiency, even higher than a dielectric phase grating. Several types of lens antennas are also presented, which show comparable performance to that of a conventional dielectric plano-hyperbolic lens antenna with similar parameters. The PASS concept is used in a beam shaping application in which a flat-topped beam antenna is designed. This work demonstrates the potential for realising thin, lightweight and low-cost antennas at Ka band, in particular for substituting higher-gain antenna technologies such as conventional dielectric shaped lens antennas.