Cylindrically conformal microstrip antennas are investigated. Two different structures, namely proximity coupled and E-shaped microstrip antennas are analyzed and information about the design parameters is obtained by means of parametric study. With these structures, cylindrical arrays, having omnidirectional radiation in the circumferential plane of the cylinder, are designed. Proximity coupled cylindrical arrays operate in the 2.3-2.4 GHz aeronautical telemetry band with approximately 4% bandwidth. On the other hand, more than 30% bandwidth is obtained by E-Shaped cylindrical array antenna structure, which also includes the commercial telemetry band. In order to verify the simulation method, a fabricated antenna in literature is simulated and acceptable agreement with simulation and fabrication results obtained.

Neste trabalho é realizada a otimização de antena de microfita banda larga usando o método de Diferenças Finitas no Domínio do Tempo (FDTD) e software comercial de onda completa. Inicialmente é feita uma introdução sobre o assunto, abordando aspectos de comunicações e de antenas de microfita, além de se fazer uma revisão bibliográfica e resumir o estado da arte sobre o tema do trabalho. A seguir, discorre-se sobre a teoria eletromagnética aplicada a antenas planares. O tópico de base é concluído com síntese dos métodos de simulação usados na análise de antenas de microfita, enfatizando o de FDTD. O próximo item revisa fundamentos teóricos e técnicas aplicadas na obtenção de banda larga em antenas de microfita. O trabalho prossegue com simulações numéricas e medidas da largura de banda, do ganho e da eficiência da antena E e de geometria inovadora aplicando técnica de alimentação capacitiva à antena E. A seguir, o algoritmo genético é apresentado e utilizado na otimização do plano de terra de antena de microfita com alimentação por sonda coaxial e também com alimentação capacitiva, para aplicações em banda larga. Resultados simulados e medidos são apresentados e boa concordância entre eles é obtida. Obteve-se 88% de largura de banda para PIFA com alimentação capacitiva e plano de terra otimizado. A tese é concluída com observações sobre os resultados apresentados e sugestões para prosseguimento e aperfeiçoamento das investigações realizadas. / In the present work, the optimization of broadband microstrip antenna employing the Finite Difference Time Domain (FDTD) and full wave commercial software are presented. First, an introduction on the subject considering main issues in communications and microstrip antennas are described, also a bibliographical review and the state of the art are presented. A review of electromagnetic theory applied to microstrip antenna is presented at the following topic, with emphasis on the FDTD method. The next step is a review of theory and techniques on bandwidth optimization of microstrip antennas. The work follows with numeric simulations and measurements on bandwidth, gain, efficiency of E shapped antenna and with a novel design procedure employing capacitive feeding on the E shapped antenna. The work follows with genetic algorithm being presented and utilized to the optimization of ground plane shape microstrip antenna with coaxial feeding and also with capacitive feeding, aiming to broadband applications. Simulated and measured results are presented. Good agreement is observed. Relative bandwidth of 88% was found for PIFA with capacitive feeding and optimized ground plane. The thesis is concluded with some comments and observations on the results obtained and suggestions for the continuation of the work.

Neste trabalho é realizada a otimização de antena de microfita banda larga usando o método de Diferenças Finitas no Domínio do Tempo (FDTD) e software comercial de onda completa. Inicialmente é feita uma introdução sobre o assunto, abordando aspectos de comunicações e de antenas de microfita, além de se fazer uma revisão bibliográfica e resumir o estado da arte sobre o tema do trabalho. A seguir, discorre-se sobre a teoria eletromagnética aplicada a antenas planares. O tópico de base é concluído com síntese dos métodos de simulação usados na análise de antenas de microfita, enfatizando o de FDTD. O próximo item revisa fundamentos teóricos e técnicas aplicadas na obtenção de banda larga em antenas de microfita. O trabalho prossegue com simulações numéricas e medidas da largura de banda, do ganho e da eficiência da antena E e de geometria inovadora aplicando técnica de alimentação capacitiva à antena E. A seguir, o algoritmo genético é apresentado e utilizado na otimização do plano de terra de antena de microfita com alimentação por sonda coaxial e também com alimentação capacitiva, para aplicações em banda larga. Resultados simulados e medidos são apresentados e boa concordância entre eles é obtida. Obteve-se 88% de largura de banda para PIFA com alimentação capacitiva e plano de terra otimizado. A tese é concluída com observações sobre os resultados apresentados e sugestões para prosseguimento e aperfeiçoamento das investigações realizadas. / In the present work, the optimization of broadband microstrip antenna employing the Finite Difference Time Domain (FDTD) and full wave commercial software are presented. First, an introduction on the subject considering main issues in communications and microstrip antennas are described, also a bibliographical review and the state of the art are presented. A review of electromagnetic theory applied to microstrip antenna is presented at the following topic, with emphasis on the FDTD method. The next step is a review of theory and techniques on bandwidth optimization of microstrip antennas. The work follows with numeric simulations and measurements on bandwidth, gain, efficiency of E shapped antenna and with a novel design procedure employing capacitive feeding on the E shapped antenna. The work follows with genetic algorithm being presented and utilized to the optimization of ground plane shape microstrip antenna with coaxial feeding and also with capacitive feeding, aiming to broadband applications. Simulated and measured results are presented. Good agreement is observed. Relative bandwidth of 88% was found for PIFA with capacitive feeding and optimized ground plane. The thesis is concluded with some comments and observations on the results obtained and suggestions for the continuation of the work.

Neste trabalho é realizada a otimização de antena de microfita banda larga usando o método de Diferenças Finitas no Domínio do Tempo (FDTD) e software comercial de onda completa. Inicialmente é feita uma introdução sobre o assunto, abordando aspectos de comunicações e de antenas de microfita, além de se fazer uma revisão bibliográfica e resumir o estado da arte sobre o tema do trabalho. A seguir, discorre-se sobre a teoria eletromagnética aplicada a antenas planares. O tópico de base é concluído com síntese dos métodos de simulação usados na análise de antenas de microfita, enfatizando o de FDTD. O próximo item revisa fundamentos teóricos e técnicas aplicadas na obtenção de banda larga em antenas de microfita. O trabalho prossegue com simulações numéricas e medidas da largura de banda, do ganho e da eficiência da antena E e de geometria inovadora aplicando técnica de alimentação capacitiva à antena E. A seguir, o algoritmo genético é apresentado e utilizado na otimização do plano de terra de antena de microfita com alimentação por sonda coaxial e também com alimentação capacitiva, para aplicações em banda larga. Resultados simulados e medidos são apresentados e boa concordância entre eles é obtida. Obteve-se 88% de largura de banda para PIFA com alimentação capacitiva e plano de terra otimizado. A tese é concluída com observações sobre os resultados apresentados e sugestões para prosseguimento e aperfeiçoamento das investigações realizadas. / In the present work, the optimization of broadband microstrip antenna employing the Finite Difference Time Domain (FDTD) and full wave commercial software are presented. First, an introduction on the subject considering main issues in communications and microstrip antennas are described, also a bibliographical review and the state of the art are presented. A review of electromagnetic theory applied to microstrip antenna is presented at the following topic, with emphasis on the FDTD method. The next step is a review of theory and techniques on bandwidth optimization of microstrip antennas. The work follows with numeric simulations and measurements on bandwidth, gain, efficiency of E shapped antenna and with a novel design procedure employing capacitive feeding on the E shapped antenna. The work follows with genetic algorithm being presented and utilized to the optimization of ground plane shape microstrip antenna with coaxial feeding and also with capacitive feeding, aiming to broadband applications. Simulated and measured results are presented. Good agreement is observed. Relative bandwidth of 88% was found for PIFA with capacitive feeding and optimized ground plane. The thesis is concluded with some comments and observations on the results obtained and suggestions for the continuation of the work.

<p>As the interest in intentional electromagnetic interference (IEMI) increases, so does the need of a suitable antenna which endures those demanding conditions. The ultrawideband (UWB) technology provides an elegant way of generating high-voltage UWB pulses which can be used for IEMI. One UWB antenna, invented solely for the purpose of radiating pulses, is the impulse radiating antenna (IRA). In the course of this master thesis work, a suitable geometry of the IRA is suggested, and modelled, for the high-voltage application of 90 kV.</p>

As the interest in intentional electromagnetic interference (IEMI) increases, so does the need of a suitable antenna which endures those demanding conditions. The ultrawideband (UWB) technology provides an elegant way of generating high-voltage UWB pulses which can be used for IEMI. One UWB antenna, invented solely for the purpose of radiating pulses, is the impulse radiating antenna (IRA). In the course of this master thesis work, a suitable geometry of the IRA is suggested, and modelled, for the high-voltage application of 90 kV.

In this thesis, the study mainly focuses on the current trends in development of compact multi-media mobile phone and provides a wideband monopole antenna design suitable for application in wireless communicating system in the near future. By utilizing the planar monopole antenna structure, the proposed antenna design is easy to be embedded into the mobile phone. Further, by using a shielding metal cover, we create a zone with low surface current distribution. This effect will reduce the electromagnetic coupling between the antenna and the electronic elements and make it possible to integrate more related elements into the mobile phones. Finally, we use the simulation software to analyze the dielectric effect caused by the casing of mobile phone and human body on the proposed antenna.

The concept for a novel new antenna design is presented and investigated for application to ground penetrating radar (GPR). The proposed new antenna design is called the shielded magnetic bowtie antenna (MBA). As the name suggests, it is predominately constructed from a bowtie-shaped volume of magnetic material that is fed from the centre of the structure by a small magnetic loop antenna. This thesis develops the magnetic antenna concept and investigates its potential for GPR predominately through numerical modelling. However, a significant part of the investigation concentrates on validating the numerical modelling technique developed to study the shielded MBA by comparing the results with measurements obtained from a scale model constructed to operate in the watertank antenna test facility, a controlled environment for GPR antenna research. The broadband properties required for GPR antennas are achieved uniquely with the shielded MBA design by a combination of the antenna shape being defined in terms of angles and an inherent magnetic loss mechanism within the antenna material structure. The design also affords an intrinsically placed antenna shield that has the potential for mitigating problems typically experienced with shielding electric dipole antennas. Antenna shielding is an important consideration for GPR antenna designers, especially given the recent US government (FCC) changes that restrict radiated energy emissions within the regulated spectrum used by GPR systems. In addition to providing the intended directional radiation properties, the magnetic antenna shield also provides an elegant solution for a low-loss wideband balun, allowing the antenna to be effectively fed from an unbalanced coaxial transmission line. Other important aspects of the proposed design are discussed in relation to the requirements for GPR antennas. Numerical models of the magnetic antenna concept show encouraging bandwidth results. For example, from a simple comparison with an equivalent sized electric bowtie antenna model, the effective gain bandwidth of the magnetic antenna is found to be at least 3-octaves compared to approximately 2-octaves for the electric bowtie. The shielded magnetic antenna achieves a gain of approximately 2 dB, compared to 5 dB for the unshielded electric bowtie antenna. However, it is noted that the magnetic antenna models contain significantly more loss compared to the electric bowtie model. The shielded MBA design emerged from a theoretical investigation of electrically small GPR antennas, given that the initial thesis objective was to investigate ways of improving low frequency GPR antennas. In general, GPR systems are operated with electric dipole antennas, such as the electric bowtie. Interestingly, the electrically small antenna investigation revealed that only the small magnetic loop (i.e., magnetic dipole) antenna can be constructed to approach, arbitrarily closely, the fundamental bandwidth limit for small antennas. This surprising and counter intuitive result is shown to be theoretically achievable with the use of magnetic materials. For the small loop antenna, energy stored within the antenna structure can be avoided by filling the antenna sphere with a perfect magnetic material. This theoretical argument is discussed and supported by numerically modelled results. The electrically small antenna investigation presented in this thesis extends to include the influence that proximity to a lossy dielectric half-space has, on improving the antenna impedance bandwidth. This investigation is of general interest for GPR; it is performed numerically and supported by measurements conducted on an experimental loop antenna situated at various heights above the ground. These results provide support for the hypothesis that a magnetic antenna may experience less influence from near-field changes in the dielectric properties of the ground compared to the equivalent sized electric field antenna.

This paper presents an overview of the research work currently being performed within the frame of project DAAB and its successor DAAB-TX towards the integration of ultra-wideband transceivers operating at mm-wave frequencies and capable of data rates up to 100 Gbits–¹. Two basic systemarchitectures are being considered: integrating a broadband antenna with a distributed amplifier and integrate antennas centered at adjacent frequencies with broadband active combiners or dividers. The paper discusses in detail the design of such systems and their components, fromthe distributed amplifiers and combiners, to the broadband silicon antennas and their single-chip integration. All components are designed for fabrication in a commercially available SiGe:C BiCMOS technology. The presented results represent the state of the art in their respective areas: 170 GHz is the highest reported bandwidth for distributed amplifiers integrated in Silicon; 89 GHz is the widest reported bandwidth for integrated-system antennas; the simulated performance of the two antenna integrated receiver spans 105 GHz centered at 148GHz, which would improve the state of the art by a factor in excess of 4 even against III-V implementations, if confirmed by measurements.

In modern digital communication, transmission and reception of information through electromagnetic signals requires digital devices that can process high data rates accurately despite being located in information heavy environments. One type of antenna receiver is the digital antenna array, which can steer its lobes electronically to increase or decrease sensitivity in specific directions. A rather recently developed system is the Wideband Digital Array Receiver, developed at Saab Surveillance in Järfälla and referred to as WiDAR. The implementations and possibilities of WiDAR are broad, but no matter its future applications, calibration is an essential feature to ensure truthful reception of data. Any type of electronic system risks errors due to hardware imperfections. The aim of this thesis is to explore and reduce these errors. Measurements with WiDAR were performed in a manner such that some of the intercepted signals were transmitted from a far away located FM and TV-mast. The data was then used to retrieve weights by calculating their relative transfer function, which were applied to calibrate all channels in the antenna array towards a chosen reference channel. These weights could then be on any accumulated set of data measured by WiDAR with hopes to compensate errors in both phase and magnitude. The results show that reducing errors this way was possible, working slightly better when calibrating phase than calibrating magnitude. If more advanced calibration is deemed necessary, further measurements could be performed to investigate where errors or variations occur by isolating different parts of the system. The calibration method used could be further developed by adding an online calibration procedure, meaning relative transfer functions are calculated in real time when performing measurements.