Array processing involves manipulation of signals induced on various antenna elements. In an adaptive array system, the radiation pattern is formed according to the signal environment by using signal processing techniques. Adaptive arrays improve the capacity of mobile communication systems by placing nulls in the direction of interfering sources and by directing independent beams toward various users. Adaptive beamforming algorithms process signals induced on each array element that are assumed not to be affected by mutual coupling between the elements. The aim of this thesis is to investigate the effects of mutual coupling on the performance of various adaptive beamforming algorithms. The performance parameters such as signal to interference plus noise ratio and speed of convergence of the adaptive algorithms are studied and compared by both neglecting and considering the mutual coupling for the least mean squares, recursive least squares, conjugate gradient and constant modulus algorithms. Finally, it is concluded that the effect of mutual coupling is major in the performance of blind algorithms rather than non-blind algorithms. The results are obtained by simulations carried out on MATLAB.

The introduction of broadband systems to communication and radar technologies has demanded the design of broadband antennas. In this thesis, broadband log-periodic dipole antennas and reflector antennas are investigated. A dual polarized log-periodic dipole antenna and a reflector antenna are designed and analyzed within the frequency band of 0.4-18 GHz. Basic theory and calculations about mutual coupling between the linear antenna elements are given. The currents at the bases of dipoles of the log-periodic antenna are found and these currents are used as inputs for the design of the reflector antenna. After the simulations made with MATLAB&Ograve / and FORTRAN, a prototype single polarized log-periodic antenna is produced. Developments on the prototype antenna are performed, both to improve the electrical characteristics of the antenna and to make the final design realizable. After the performance of the single polarized log-periodic antenna is found satisfactory, dual polarized antenna is produced. Performances of both single and dual polarized log-periodic antennas are measured in the anechoic chamber at ASELSAN&reg / Inc. After the measurements of the antenna, using the currents at the bases of the dipoles, a reflector antenna is designed using &ldquo / MIR&rdquo / program written in FORTRAN, which is based on physical optics method. A method to calculate the aperture blockage of the reflector is developed. Simulation results of reflector antenna are given.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2018-05-29T12:47:57Z No. of bitstreams: 2 Dissertação - André Almeida Souza Coelho - 2018.pdf: 12771064 bytes, checksum: b6418151bb082eeffbdb1692392e483e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-05-29T12:49:33Z (GMT) No. of bitstreams: 2 Dissertação - André Almeida Souza Coelho - 2018.pdf: 12771064 bytes, checksum: b6418151bb082eeffbdb1692392e483e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-05-29T12:49:33Z (GMT). No. of bitstreams: 2 Dissertação - André Almeida Souza Coelho - 2018.pdf: 12771064 bytes, checksum: b6418151bb082eeffbdb1692392e483e (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-02-19 / This work deals with the problem of estimation of incident angles (DOA) of plane waves on a linear array of sensors taking into account the mutual coupling between the sensors. MUSIC and SEAD methods are analyzed with and without coupling, in the cases of correlated and uncorrelated signals, and a compensation method is applied to minimize estimation errors. Several results are obtained and the statistical performance of MUSIC and SEAD is evaluated, proposing an application scenario for SEAD when under the influence of mutual coupling between the sensors. / Este trabalho aborda o problema de estimação de ângulos de incidência (DOA) de ondas planas sobre um arranjo linear de sensores levando em consideração o acoplamento mútuo entre os sensores. São analisados os métodos MUSIC e SEAD com e sem acoplamento, nos casos de sinais descorrelacionados e correlacionados, e aplicado um método de compensação para minimizar os erros de estimação. Diversos resultados são obtidos e o desempenho estatístico do MUSIC e SEAD é avaliado, propondo um cenário de aplicação para o SEAD quando sob a influência do acoplamento mútuo entre os sensores.

Although multi-element antenna (MEA) systems are already used in some modern wireless communication systems, the issue of mutual coupling between elements remains a challenge during MEA system design. Indeed, communications engineers continue to bemoan the fact that that the antenna elements are often still designed with such coupling as an afterthought. Thus, some authors have used the decoupling surface (DS) idea, whereby a separate DS is added to the MEA systems to reduce the above coupling. Whereas a DS may indeed lower the coupling levels between the elements of a given MEA system, it usually changes the other performance parameters as well, and in an undesirable way. Thus, this design route is a complicated one that is not easily affected. In this thesis we propose, for the first time, a new design process for MEA systems based on shape synthesis. The MEA system performance indicators are combined into an objective that sets the goal of the shape synthesis procedure. The application of the proposed design process is illustrated for three different geometrical arrangements of patch antennas and decoupling surfaces. This confirms the efficacy of the new design method.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23206号 / 工博第4850号 / 新制||工||1757(附属図書館) / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 篠原 真毅, 教授 和田 修己, 教授 山本 衛 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

This work continues the development of phased array radar for UAS detection and tracking. The earlier 1D scanning, 4 channel BYU SAA radar is improved upon and replicated to form a network of radars. These are shown to work together for higher level tracking across multiple fields of view. Additionally, a new phased array instrument is designed and constructed with 16 channels, 2D scanning, and improved signal processing algorithms. Preliminary metrics and field results show the operation of this sensor. A new technique for measuring array mutual impedances from embedded element patterns is developed here. This technique uses an antenna range instead of a network analyzer. New mathematical relationships are built to handle cases for practical measurements and field transformations. Demonstration of this method with a 2x2 uniform rectangular array is shown and compares favorably with the mutual impedances traditionally measured with a network analyzer. A new way to measure radiation efficiency using the antenna Y factor method is demonstrated. This method does not require an expensive field measurement chamber and can be done with a simple ground shield and absorber foam. Various X band antennas have their radiation efficiency characterized and compare favorable with known efficiencies.

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No / This article presents a printed crescent-shaped monopole MIMO diversity antenna for wireless communications. The port-to-port isolation is increased by introducing an I-shaped conductor symmetrically between the two antenna elements and shaping the ground plane. Both the computed and experimental results confirm that the antenna possesses a wide impedance bandwidth of 54.5% across 1.6-2.8 GHz, with a reflection coefficient and mutual coupling better than -10 and -14 dB, respectively. By further validating the simulated and the measured radiation and MIMO characteristics including far-field, gain, envelope correlation and channel capacity loss, the results show that the antenna can offer effective MIMO/diversity operation to alleviate multipath environments.

Yes / In this paper, we present an analytical study for the investigation of the effects of the magnetoelectric elements of a reciprocal and nonreciprocal bianisotropic grounded substrate on the input impedance, resonant length of a dipole antenna as well as on the mutual coupling between two element printed dipole array in three configuration geometries: broadside, collinear and echelon printed on the same material. This study examines also the effect of the considered bianisotropic medium on the electric and magnetic field distributions that has been less addressed in the literature for antenna structures. Computations are based on the numerical resolution, using the spectral method of moments, of the integral equation developed through the mathematical derivation of the appropriate spectral Green’s functions of the studied dipole configuration. Original results, for chiral, achiral, Tellegen and general bi-anisotropic media, are obtained and discussed with the electric and magnetic field distributions for a better understanding and interpretation. These interesting results can serve as a stepping stone for further works to attract more attention to the reciprocal and non-reciprocal Tellgen media in-depth studies.