As ubiquitous wireless communication becomes part of life, the demand on antenna miniaturization and interference reduction becomes more extreme. However, antenna size and performance are limited by radiation physics, not technology. In order to understand antenna radiation and energy storage mechanisms, classical and alternative viewpoints of radiation are discussed. Unlike the common sense of classical antenna radiation, it is shown that the entire antenna fields contribute to both radiation and energy storage with varying total energy velocity during the radiation process. These observations were obtained through investigating impedance, power, the Poynting vector, and energy velocity of a radiating antenna. Antenna transfer functions were investigated to understand the real-world challenges in antenna design and overall performance. An extended model, using both the singularity expansion method and spherical mode decomposition, is introduced to analyze the characteristics of various antenna types including resonant, frequency-independent, and ultra-wideband antennas. It is shown that the extended model is useful to understand real-world antennas. Observations from antenna radiation physics and transfer function modeling lead to both corrections and extension of the classical fundamental-limit theory on antenna size. Both field and circuit viewpoints of the corrected limit theory are presented. The corrected theory is extended for multi-mode excitation cases and also for ultra-wideband and frequency-independent antennas. Further investigation on the fundamental-limit theory provides new innovations, including a low-Q antenna design approach that reduces antenna interference issues and a generalized approach for designing an antenna close to the theoretical-size limit. Design examples applying these new approaches with simulations and measurements are presented. The extended limit theory and developed antenna design approaches will find many applications to optimize compact antenna solutions with reduced near-field interactions. / Ph. D.

Virginia Tech, Utah State University, and the University of Washington were teamed to form the Ionospheric Observation Nanosat Formation to investigate formation-flying requirements for multiple spacecraft missions. A communication subsystem for the mission will comprise an uplink, downlink and a satellite-to-satellite crosslink. A linearly polarized resonant loop antenna mounted above the bottom surface of the spacecraft was selected for a possible satellite uplink receive antenna. The resonant loop was chosen to satisfy the physical requirements of the spacecraft whild still achieving efficient operation for a UHF signal. A full-scale prototype was fabricated to measure frequency dependent characteristics of the antenna. A gamma match and a quarter-wave sleeve balun transformer were integrated to the system to minimize the power reflected at the antenna input and to isolate the antenna from the feed line. The uplink antenna demonstrated sufficient performance; however, the final bandwidth of less than one percent will require additional tuning as other subsystems are integrated into the final flight-ready prototype. / Master of Science

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.

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

The ocean symbolizes mystery, passion, and power. However, most of the ocean, about 80 %, is unknown to humans. AUVs (Autonomous Underwater Vehicles) provide a platform where terrain mapping, the biodiversity, and the resource survey of the ocean become accessible. Unlike ROVs (Remotely Operated Vehicle), AUVs operate according to their preset program which specifies the instructions required in different environments. One design aspects of AUVs that must be considered is that the data it acquire needs to be transmitted to a ground station (typically a ship). Although underwater acoustic communication is available nowadays, the low transmission rate and narrow bandwidth makes it unsuitable for large data transmission. For large sets of data, transmission with electromagnetic waves is more suitable. LoLo is an AUV which is designed and assembled at KTH Royal Institute of Technology, Sweden. Its wireless communication system consists of five components: RC (radio communication, 2.4 GHz), RF (radio frequency, 868 MHz), WIFI (wireless fidelity, 2.4 GHz), 4G (4th generation, 800 MHz, 1.8 GHz and 2.6 GHz) and GPS (global positioning system, 1.575 GHz). The goal of this project is to design an antenna board where the five subsystems are integrated. Importantly, due to the influence of seawater and waves, the resonant frequency of the antenna will fluctuate to a certain extent. Therefore, we need a robust, and preferably broadband, antenna system. In this project, we integrated printed dipole and monopole antennas on a single circuit board. The printed dipole antennas operate over a reasonable bandwidth and their radiation pattern is omnidirectional. The monopole antenna is designed to have multiple resonant frequencies which can cover BAND 20 (800 MHz) and BAND 3 (1.8 GHz) of the 4G service in Sweden. The 4G antenna shows good omnidirectional characteristics in the lower frequency band (band 20) and broadband characteristic in the higher frequency band. The upper 4G band is to be used to transmit large sets of data if a signal can be detected. The lower 4G band is added to provide redundancy. The antenna board is manufactured and measured. The results show the consistency with the simulation results and meets the requirement of the project. / Havet symboliserar mysterium, passion och kraft. Men det mesta av havet, cirka 80 %, är okänt för människor. AUVs (Autonomous Underwater Vehicles) är en plattform där terrängkartläggning, biologisk mångfald och resursundersökning blir tillgänglig. Till skillnad från ROVs (Remotely Operated Vehicles) fungerar AUVs enligt sitt förinställda program som specificerar de instruktioner som krävs i olika miljöer. Den data som den förvärvade måste överföras till en markstation (oftast en båt). Även om akustiska kommunikationen under vatten är möjlig idag gör den låga överföringshastigheten och den smala bandbredden den olämplig för stora dataöverföringar. I dessa fall är det bättre att överföra data med hjälp av elektromagnetiska vågor. LoLo är en AUV som är designad på KTH Royal Institute of Technology, Sverige. Dess trådlösa kommunikationssystem består av fem delsystem: RC (radiokommunikation, 2.4 GHz), RF (radiofrekvens, 868 GHz), WIFI (trådlös fidelity, 2.4 GHz), 4G (4 generationen av mobilnätverket, 800 MHz och 1.8 GHz) och GPS (global positioning system, 1.575 GHz). Målet med detta projekt är att designa antennerna för dessa fem delsystem. Viktigt att notera är antennernas resonansfrrekvens påverkas till viss del av havsvatten och vågor. Därför behövs vi ett robust, bredbandsantennsystem. I detta projekt integrerade vi dipolantenner och en monopolantenn på ett kretskort. Dipolantennerna har rimlig bandbredd och är omnidirektionella. Monopolantennen ger oss flera resonansfrekvenser som kan täcka Band 20 (800 MHz) och Band 3 (1.8 GHz) av 4Gspektrumet i Sverige. 4Gantennen visar omnidirektionella strålningsegenskaper i det lägre band et (band 20) och har vred bandbredd i det högre band et. Det högre bandet kommer användas för att skicka mycket data om en signal kan säkras. Det lägre bandet ger redundans. Antennen tillverkas och mäts i ett ekofritt rum. Mätresultaten stämmer överens med simuleringsresultaten och uppfyller projektets krav.

The demand of wireless communication has increased significantly in the past few decades due to huge demand to deliver multimedia content instantly. The expansion of mobile content paired with affordable mobile devices has opened a new trend for having access to the latest information on mobile devices. This trend is made possible by the technology of smart antenna systems as well as array signal processing algorithms. Array signal processing is not limited to wireless communication, but also found in other applications such as radar, sonar and automotive. One of the important components in array signal processing is its ability to estimate the direction of incoming signals known as directional-of-arrival (DOA). The performance of DOA algorithms depends on the steering vector since it contains information about the direction of incoming signals. One of the main factors to affect the DOA estimation is the array geometries since the array factor of the array geometries determines the definition of the steering vector. Another issue in DOA estimation is that the DOA algorithms are designed based on the ideal assumption that the antenna arrays are free from imperfection conditions. In practice, ideal conditions are extremely difficult to obtain and thus the imperfect conditions will severely degraded the performance of DOA estimation. The imperfect conditions include the presence of mutual coupling between elements and are also characteristic of directional antenna. There are three topics being discussed in this thesis. The first topic being investigated is new geometry of antenna array to improve the performance of DOA estimation. Two variants of the circular-based array are proposed in this thesis: semi-circular array and oval array. Another proposed array is Y-bend array, which is a variant of V-shape array. The proposed arrays are being put forward to offer a better performance of DOA estimation and have less acquired area compared with the circular array. It is found out that the semi-circular array has 5.7% better estimation resolution, 76% lower estimation error, and 20% higher estimation consistency than the circular array. The oval array improves the estimation resolution by 33%, estimation error by 60%, and estimation consistency by 20% compared with the circular array. In addition, for the same number of elements, the oval array requires 12.5% to 15% less area than the circular array. The third proposed array, Y-bend array, has 23% smaller estimation resolution, 88% lower estimation error, and 7% higher estimation consistency than the V-shape array. Among the proposed arrays, the semi-circular possessed the best performance with 25% smaller estimation resolution, ten times smaller estimation error, and 5% higher estimation consistency over the other proposed arrays. Secondly, this thesis investigates the DOA estimation algorithm when using the directional antenna array. In this case, a new algorithm is proposed in order to suit the characteristics of the directional antenna array. The proposed algorithm is a modified version of the Capon algorithm, one of the algorithms in beamforming category. In elevation angle estimation, the proposed algorithm achieves estimation resolution up to 1°. The proposed algorithm also manages to improve the estimation error by 80% and estimation consistency by 10% compared with the Capon algorithm. In azimuth angle estimation, the proposed algorithm achieves 20 times lower estimation error and 20% higher estimation consistency than the Capon algorithm. These simulation results show that the proposed algorithm works effectively with the directional antenna array. Finally, the thesis proposes a new method in DOA estimation process for directional antenna array. The proposed method is achieved by means of modifying covariance matrix calculation. Simulation results suggest that the proposed method improves the estimation resolution by 5° and the estimation error by 10% compared with the conventional method. In summary, this thesis has contributed in three main topics related to DOA estimation; array geometry design, algorithm for the directional antenna array, and method in DOA estimation process for the directional antenna array.

The performance and advantages of microstrip patch antennas such as lowweight, low profile, and low cost made them the perfect choice forcommunication systems engineers. They have the capability to integrate withmicrowave circuits and therefore they are very well suited for applications suchas cell devices, WLAN applications, navigation systems and many othersIn this thesis; a compact rectangular patch antennas are designed and tested forGPS devices at 1.57542 GHz, and for a satellite TV signal at 11.843 GHz and11.919 GHz. The final part of this work has been concentrated on studying anarray antenna with two and four elements. The antennas of the design examplesof this work has been manufactured and tested in laboratory.

Lee Wai Ki. / Thesis submitted in: May 2004. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 62-66). / Abstracts in English and Chinese. / Chapter Chapter 1: --- Introduction --- p.8 / Chapter 1.1 --- Motivation --- p.8 / Chapter 1.2 --- Organization of the thesis --- p.10 / Chapter Chapter 2: --- Background Technology --- p.12 / Chapter 2.1 --- Introduction: FUZZY EM CAD formula for impedance of the edge of the patch antenna --- p.12 / Chapter 2.2 --- Fringe field extension of the patch: --- p.12 / Chapter 2.2.1 --- Applying the root of area capacitance formula --- p.12 / Chapter 2.2.2 --- Defining microstrip parallel plate capacitor with infinite substrate --- p.13 / Chapter 2.2.3 --- The parallel plate capacitor formula --- p.14 / Chapter 2.2.4 --- DC fringe field leading to the patch extension --- p.15 / Chapter 2.3 --- Cavity model of the patch --- p.16 / Chapter 2.3.1 --- Cavity model analysis on its internal field --- p.16 / Chapter 2.3.2 --- Input impedance derived from cavity model --- p.19 / Chapter 2.3.3 --- Quality factor of patch antenna --- p.19 / Chapter 2.4 --- Fringe extension applied to cavity model in RF --- p.23 / Chapter Chapter 3: --- Simple one Port wide band multi-layer patch Antenna --- p.24 / Chapter 3.1 --- Introduction --- p.24 / Chapter 3.2 --- Antenna design --- p.25 / Chapter 3.3 --- Measured results --- p.26 / Chapter 3.4 --- Antenna Analysis --- p.29 / Chapter 3.5 --- Conclusion --- p.30 / Chapter Chapter 4: --- Design synthesis of patch antennas of the T-square Probe --- p.31 / Chapter 4.1 --- Introduction --- p.31 / Chapter 4.2 --- The physics interpretation --- p.32 / Chapter 4.3 --- The Smith chart movement by the T-square feed on the patch --- p.33 / Chapter 4.4 --- Conclusion --- p.35 / Chapter Chapter 5: --- Design synthesis of the wideband tuning-fork-shaped feeding for patch antenna --- p.36 / Chapter 5.1 --- Introduction --- p.36 / Chapter 5.2 --- Antenna design --- p.36 / Chapter 5.3 --- The Smith chart movements of the tuning-fork shaped feeding on the patch --- p.37 / Chapter 5.4 --- Conclusion --- p.41 / Chapter Chapter 6: --- "Fork on H-slot feed of multilayer microstrip antenna for wideband, high isolation and low cross polarization" --- p.42 / Chapter 6.1 --- Introduction --- p.42 / Chapter 6.2 --- Antenna analysis - Isolation improvement considerations --- p.44 / Chapter 6.3 --- Antenna design and measured results --- p.46 / Chapter 6.3.1 --- The simulated return loss and current distribution s in various structure of the two port. --- p.47 / Chapter 6.3.2. --- The hardware and the comparison of results --- p.50 / Chapter 6.3.3. --- The simulated properties of the radiation patterns and cross-polarizations --- p.52 / Chapter 6.3.4. --- The comparison of radiation patterns between simulation and hardware --- p.56 / Chapter 6.4 --- Further improvements --- p.58 / Chapter 6.5 --- Conclusion --- p.59 / Chapter Chapter 7: --- Conclusions --- p.60 / Reference --- p.62 / List of Publication --- p.66

Un des enjeux majeurs dans l'intégration de nouveaux systèmes de guerre électronique (GE) dans les avions d'armes est notamment la réduction de l'encombrement des antennes. En GE, La bande passante des antennes peut être de l'ordre de la décade et la fréquence basse peut être voisine de la centaine de MHz, ce qui rend l'intégration des antennes difficile voire impossible selon les cas. Les antennes de GE font habituellement appel à des antennes dites "indépendantes de la fréquence" placées au-dessus d'une cavité absorbante. La fabrication des matériaux absorbants est à ce jour encore "artisanale" et donc onéreuse. De plus, ces matériaux sont lourds et ils ne présentent pas les mêmes caractéristiques électriques d'une fabrication à l'autre. Les travaux présentés dans ce manuscrit sont dédiés à la réalisation d'antennes à très large bande passante de très faible épaisseur et sans absorbant. Nous avons proposé et validé une nouvelle structure basée sur les matériaux à bandes interdites électromagnétiques (BIE). Le nouveau dispositif permet de remplacer les matériaux absorbants, de réduire l'épaisseur des antennes large bande et de réduire les coûts de fabrication grâce à un procédé industriel de fabrication. La nouvelle structure présente contrairement à toutes les autres structures BIE l'avantage d'être ultra large bande et compacte (de l'ordre de 1/100ième de longueur d'onde d'épaisseur). Nous avons montré l'intérêt d'utiliser un tel dispositif pour réduire l'épaisseur et améliorer les performances des antennes planaires de forme et de polarisation quelconque.

Typically, MAC protocols for mobile ad hoc networks assume omnidirectional antennas, and use of directional antennas offers many advantages, such as range extension, reduced co-channel interference, increased the degree of spatial reuse, improved the throughput of networks, and reduced the transmission power. There are many wireless ad hoc MAC protocol have been proposed. However, these protocols do not provide significant improvement of network performance because they can¡¦t let nodes to support multiple simultaneous transmissions or receptions ability. In this paper, we proposed a newly designed MAC protocols, we used adaptive beam-forming system to reduce the co-channel interference problem, and our proposed MAC protocol will enable nodes with multiple simultaneous transmissions and receptions ability. The handshake mechanism of proposed MAC protocol is that used receiver initialize handshake mechanism such as MACA/BI. We changed the Ready-to-Receive (RTR) control packet, which was used to poll neighbor nodes to be a dual-used control packet, Ready-to-Receive-Transmission (RTRT). Our simulation results will show that our proposed MAC protocol do exploit the advantage of space division multiple access that significantly reduced the problem of poor networks throughput which caused by bottleneck nodes in wireless ad hoc networks.