ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, California / There are always some intrinsic tradeoffs among the performance characteristics: radiation efficiency, directivity, and bandwidth, of electrically small antennas (ESAs). A non-Foster enhanced, broad bandwidth, metamaterial-inspired, electrically small, Egyptian axe dipole (EAD) antenna has been successfully designed and measured to overcome two of these restrictions. By incorporating a non-Foster circuit internally in the near-field resonant parasitic (NFRP) element, the bandwidth of the resulting electrically small antenna was enhanced significantly. The measured results show that the 10 dB bandwidth (BW10dB) of the non-Foster circuit-augmented EAD antenna is more than 6 times the original BW10dB value of the corresponding passive EAD antenna.

We developed curved spiral antennas for use in underwater (freshwater) communications. Specifically, these antennas will be integrated in so-called mussel backpacks. Backpacks are compact electronics that incorporate sensors and a small radio that operate around 300 MHz. Researchers attach these backpacks in their freshwater mussel related research. The antennas must be small, lightweight, and form-fit the mussel. Additionally, since the mussel orientation is unknown, the antennas must have broad radiation patterns. Further, the electromagnetic environment changes significantly as the mussels burrow into the river bottom. Broadband antennas, such a spiral antennas, will perform better in this instance. While spiral antennas are well established, there has been little work on their performance in freshwater. Additionally, there has been some work on curved spiral antennas, but this work focused on curving in one dimension, namely curving around a cylinder. In this thesis we develop spiral antennas that curve in two dimensions in order to conform the contour of a mussel's shell. Our research has three components, namely (a) an investigation of the relevant theoretical underpinning of spiral antennas, (b) extensive computer simulations using state-of-the art computational electromagnetics (CEM) simulation software, and (c) experimental validation. The experimental validation was performed in a large tank in a laboratory setting. We also validated some designs in a pool (∼300,000 liters of water and ∼410 squared-meter dive pool) with the aid of a certified diver. To use CEM software and perform successful antenna-related experiments require careful attention to many details. The mathematical description of radiation from an antenna, antenna input impedance and so on, is inherently complex. Engineers often make simplifying assumptions such as assuming no reflections, or an isotropic propagation environment, or operation in the antenna far field, and so on. This makes experiments on antennas challenging since it often quite difficult to replicate the simplifying assumptions in an experimental setting. Still, with careful consideration of the important factors and careful experimental design it is possible to perform successful experiments. For example, antenna measurements are often performed in anechoic chambers. For our research we used a large swimming pool to mimic an underwater anechoic chamber. Our CEM simulations and experimental results are in most cases congruent. We are confident that we can design formfitting, compact (spiral) antennas that one could deploy on mussels. This will greatly enhance the mussel backpacks that are used by researchers at the University of Iowa.

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In this dissertation, many novel low-cost planar antenna designs are presented for on-vehicle applications. Promising planar antennas showing the desired broadside and omnidirectional radiation patterns and having low-profile configurations are demonstrated. Also, studies on controlling the radiation patterns are conducted. Details of the measured and simulated results of the studied antennas are presented and discussed.

In this dissertation, a series of printed multiband antennas for slim mobile communication devices are presented. The study mainly focuses on how to effectively enhance the impedance bandwidth. With the equivalent LC matching circuit integrated in the antennas, wide impedance bandwidth can be obtained without increasing the size of the antennas. Note that the equivalent matching circuit can be formed by the coupling strip and the shorting strip to generate capacitance and inductance, respectively. In addition, the effects on the user's hand, head and whole body will be analyized. Also, the issue of the hearing aid compatibility will be discussed in this dissertation.

In this dissertation, a variety of novel mutiband WWAN loop antennas are presented. By designing proper coupled-fed mechanisms for the proposed loop antennas, the impedance bandwidth of the loop antenna can be greatly enhanced to achieve two wide operating bandwidths at antenna¡¦s lower and upper bands to easily cover GSM850/900/1800/1900/UMTS operation. With two wider operating bandwidths obtained, the tolerance of frequency detuning and the capability of bandwidth tuning of the loop antennas can be improved for practical applications. In addition, in order to find methods to meet the SAR and HAC criterions, the proposed small-size chip loop antenna studied in this dissertation which is suitable for both bar-type and folder-type mobile phone applications are simulated and analyzed for SAR and HAC issues.

Made available in DSpace on 2014-12-17T14:55:53Z (GMT). No. of bitstreams: 1 JoseHCM_DISSERT.pdf: 1439414 bytes, checksum: f96f0decdde25078b5110927edf3b75c (MD5) Previous issue date: 2011-12-19 / This work presents techniques used to design and manufacture microstrip patch antennas for applications in portable and mobile devices. To do so, are evaluated several factors that can influence the performance of microstrip patch antennas. Miniaturization techniques are studied and employed in order to apply this type of antenna in mobile and / or mobile. The theories of microstrip patch antennas are addressed by analyzing characteristics such as constitution, kinds of patches, substrates, feeding methods, analysis methods, the main advantages and disadvantages and others. Techniques for obtaining broadband microstrip patch antennas were surveyed in literature and exemplified mainly by means of simulations and measurements. For simulations of the antennas was used the commercial software . In addition, antenna miniaturization techniques have been studied as a main concern the fundamental limits of antennas with special attention to electrically small antennas because they are directly linked to the microstrip patch antennas. Five design antennas are proposed to demonstrate the effectiveness of techniques used to obtain the microstrip patch antennas broadband and miniaturized for use in mobile devices and/or portable. For this, the proposed antennas were simulated, built and measured. The antennas are proposed to be used in modern systems of wireless communications such as DTV, GPS, IEEE 802.16, IEEE 802.11, etc. The simulations of the antennas were made in business and computer programs. The measured results were obtained with a parser Vector of networks of the Rhode and Schwarz model ZVB 14 / Esse trabalho apresenta t?cnicas usadas para projetar e fabricar antenas patch de microfita para aplica??es em dispositivos port?teis e m?veis. Para isso, s?o avaliados diversos fatores que podem influenciar no desempenho das antenas patch de microfita. T?cnicas de miniaturiza??o s?o estudadas e empregadas visando a aplica??o deste tipo de antena em dispositivos port?teis e/ou m?veis. Fundamentos te?ricos sobre as antenas patch de microfita s?o abordados analisandose caracter?sticas como: constitui??o, tipos de patches, substratos, m?todos de alimenta??o, m?todos de an?lises, principais vantagens e desvantagens dentre outros. T?cnicas para obten??o de antenas patch de microfita banda larga foram pesquisadas na literatura e exemplificadas principalmente por meio de simula??es e medi??es. Para as simula??es das antenas foi utilizado o programa computacional comercial . Al?m disso, t?cnicas de miniaturiza??o de antenas foram estudadas tendo como preocupa??o principal os limites fundamentais das antenas com aten??o especial a antenas eletricamente pequenas por estarem diretamente vinculadas ?s antenas patch de microfita. Cinco projetos de antenas s?o propostos para comprovar a efici?ncia das t?cnicas utilizadas para obten??o de antenas patch de microfita banda larga e miniaturizadas, para aplica??o em dispositivos m?veis e/ou port?teis. Para isso, as antenas propostas foram simuladas, constru?das e medidas. As antenas foram propostas para serem utilizadas em sistemas modernos de comunica??es sem fio como: DTV, GPS, IEEE 802.16, IEEE 802.11, etc. As simula??es das antenas foram feitas nos programas computacionais comerciais e . Os resultados medidos foram obtidos com um analisador vetorial de redes da Rhode and Schwarz modelo ZVB 14