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The mutual coupling in phased array is a well-known phenomenon. It affects the active element pattern of the array as the phase of the individual element is altered. In an array that has many elements, the effect is identical for all the elements that are nearer to the center of the antenna, thus allowing a more predictable scan performance with respect to the phase of the elements. However, in a small array that has only three elements, the active element pattern for the elements at the end can be significantly different from the center element and this affects the predictability of operations such as direction finding. The thesis investigates two ways that can potentially reduce or at least control the mutual coupling in small arrays. The first method simply adds a dummy element with a special load condition to each end of the array to make the edge element "feel" as if there are more elements next to it. The second method uses a passive feedback circuit to both monitor and correct the magnitude and phase of the mutual coupling at the input of each array element. A hybrid ring is attached to each of the elements to monitor the amount of interference received by that element. Simulation results for the dummy element method shows that some reduction in phase error can be achieved if the spacing and length of the element are selected properly. The compensation network approach relies on an efficient two-port array element. The research has focused on the design of a two-port printed circuit dipole that could be used in such an array. The dipole was designed, simulated, and fabricated. Future research will use this element in a compensation network. / Republic of Singapore Navy author.

A thesis submitted to the Faculty of Engineering. University of the Witwatersrand. Johannesburg in fulfilment of the requirements for the degree of Doctor of Philosophy. / The general argument of the thesis is that the design of broadband antennas demands a thorough understanding of the factors influencing the current distribution on antenna wires. Specifically. current distribution concepts are used to improve the evaluation and design of small broadband antennas for the high frequency (HF) 2 to 30 MHz range. The current distribution on an antenna governs its input impedance, radiation efficiency and radiation patterns. (Abbreviation abstract) / Andrew Chakane 2018

by Tam Wai Yip. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaves 139-145). / Acknowledgments --- p.iii / Abstract --- p.iv / List of Symbols --- p.xi / List of Figures --- p.xvii / Chapter 1. --- Introduction / Chapter 1.1 --- Brief Review --- p.1 / Chapter 1.2 --- Statement of Problem --- p.5 / Chapter 1.3 --- Organization --- p.6 / Chapter 2. --- Spherical Circular and Annular Microstrip Antenna / Chapter 2.1 --- Introduction --- p.9 / Chapter 2.2 --- Vector Legendre Series Formulation --- p.10 / Chapter 2.3 --- Galerkin's Procedure --- p.17 / Chapter 2.4 --- Input Impedance --- p.20 / Chapter 2.5 --- Far Zone Radiation Pattern --- p.20 / Chapter 2.6 --- Radiation Resistance using Electric Surface Current Model --- p.22 / Chapter 2.7 --- Numerical Examples --- p.24 / Chapter 2.7.1 --- Input Impedance --- p.25 / Chapter 2.7.2 --- Resonance Radiation Resistance --- p.29 / Chapter 2.7.3 --- Far Zone Radiation Pattern --- p.35 / Chapter 2.8 --- Summary --- p.41 / Chapter 3. --- Cylindrical Rectangular Microstrip Antenna with Coplanar Elements / Chapter 3.1 --- Introduction --- p.42 / Chapter 3.2 --- Integral Equation Formulation --- p.44 / Chapter 3.3 --- Input Impedance with Coplanar Parasitic Elements --- p.50 / Chapter 3.4 --- Far Zone Radiation Pattern --- p.51 / Chapter 3.5 --- Mutual Coupling between Antennas --- p.52 / Chapter 3.6 --- Numerical Examples --- p.56 / Chapter 3.6.1 --- Input Impedance with Coplanar Parasitic Elements --- p.56 / Chapter 3.6.2 --- Mutual Coupling between Antennas --- p.76 / Chapter 3.7 --- Summary --- p.85 / Chapter 4. --- Aperture Coupled Rectangular Cylindrical Microstrip Antenna / Chapter 4.1 --- Introduction --- p.86 / Chapter 4.2 --- Integral Equation Formulation using Reciprocity Method --- p.89 / Chapter 4.3 --- Input Impedance of a Stripline Feed Aperture Coupled Microstrip Antenna --- p.99 / Chapter 4.4 --- Input Impedance of a Microstrip Line Feed Aperture Coupled Microstrip Antenna --- p.100 / Chapter 4.5 --- Numerical Examples --- p.101 / Chapter 4.5.1 --- Stripline Feed Antennas --- p.101 / Chapter 4.5.2 --- Microstrip Line Feed Antennas --- p.110 / Chapter 4.6 --- Summary --- p.115 / Chapter 5. --- Green's Functions for a Electric Current on a Dielectric Coated Sphere / Chapter 5.1 --- Expansion of Fields using Spherical Harmonics --- p.116 / Chapter 5.2 --- Green's Functions in Spectral Domain --- p.119 / Chapter 6. --- Green's Functions for a Current on a Dielectric Coated Cylinder / Chapter 6.1 --- Expansion of Fields with Auxiliary Potentials --- p.121 / Chapter 6.2 --- Green's Functions in Spectral Domain --- p.125 / Chapter 7. --- Green's Functions for a Current inside a Triple Layered Cylinder / Chapter 7.1 --- Expansion of Fields with Auxiliary Potentials --- p.129 / Chapter 7.2 --- Green's Functions in Spectral Domain --- p.132 / Chapter 8. --- Conclusions and Recommendations / Chapter 8.1 --- Conclusions --- p.137 / Chapter 8.2 --- Recommendations for Future Research --- p.138 / References --- p.139 / Appendices / Chapter A. --- Vector Legendre Series --- p.146 / Chapter B. --- Surface Current for Spherical Microstrip Antenna --- p.149 / Chapter C. --- Modified Reciprocity Theorem --- p.152 / Chapter D. --- Spherical Bessel Functions and Legendre Functions --- p.154 / Chapter E. --- Approximated Green's functions Gθθ and Gφφ for large n --- p.157 / Chapter F. --- Current Distributions for Cylindrical Rectangular Microstrip Antenna --- p.163 / Chapter G. --- "Evaluation of Zijmn, V1imand V2im" --- p.165 / Chapter H. --- Deformation of Integration of Path --- p.169 / Chapter I. --- Hankel Functions --- p.170 / Chapter J. --- Current Distributions for Aperture Coupled Antenna --- p.172 / Chapter K. --- "Evaluation of ΔV，Ye1, Ye2, Yai , Vi and Zij" --- p.176 / Chapter L. --- Program Listing for stripline Feed Aperture Coupled Microstrip Antenna --- p.178

As recentes aplicações que utilizam bandas ultralargas e comunicação pulsada necessitam de antenas adaptadas às suas necessidades. Para tanto, é necessário entender melhor o funcionamento dessas antenas em toda a banda utilizada e sua resposta aos pulsos de entrada. Nesse sentido, algumas ferramentas de análise de antenas no domínio do tempo foram desenvolvidas e utilizadas de modo a explicar o mecanismo de radiação de algumas antenas. Através da utilização de estruturas grandes com relação à duração do pulso de entrada, é possível identificar como o pulso se propaga e é refletido pela estrutura. Em seguida, é estabelecida a relação entre a localização do pulso e a radiação gerada pela geometria da antena nessa posição. Com isso se pode identificar as origem das características da resposta impulsiva da antena e a sua relação com a aceleração de cargas que ocorre na estrutura. Finalmente, são apresentados alguns resultados relacionados ao desempenho da antena como dispersão, distorção e diagrama de radiação de energia normalizado. / The recent applications that uses UWB and pulse communications demands antennas that fits better its constraints. Therefore, it is necessary to understand the behaviour of these antennas in all the bandwidth used and its response to input pulses. With this objective, some analysis tools for antennas in the time domain have been developed. These tools provided and explanation to the radiation mechanism of some antennas. Through the use of large structures with respect to the duration of the input pulse it is possible to identify how the pulse propagates and how it is reflected by the structure. The relationship between the pulse position and the radiation of the antenna is then established for every position. This procedure enables the identification of the relationship between the antenna impulse response and the acceleration of charges in the structure. Finally, we present some results related to the performance of the antenna such as dispersion, distortion and normalized energy radiation pattern.

As recentes aplicações que utilizam bandas ultralargas e comunicação pulsada necessitam de antenas adaptadas às suas necessidades. Para tanto, é necessário entender melhor o funcionamento dessas antenas em toda a banda utilizada e sua resposta aos pulsos de entrada. Nesse sentido, algumas ferramentas de análise de antenas no domínio do tempo foram desenvolvidas e utilizadas de modo a explicar o mecanismo de radiação de algumas antenas. Através da utilização de estruturas grandes com relação à duração do pulso de entrada, é possível identificar como o pulso se propaga e é refletido pela estrutura. Em seguida, é estabelecida a relação entre a localização do pulso e a radiação gerada pela geometria da antena nessa posição. Com isso se pode identificar as origem das características da resposta impulsiva da antena e a sua relação com a aceleração de cargas que ocorre na estrutura. Finalmente, são apresentados alguns resultados relacionados ao desempenho da antena como dispersão, distorção e diagrama de radiação de energia normalizado. / The recent applications that uses UWB and pulse communications demands antennas that fits better its constraints. Therefore, it is necessary to understand the behaviour of these antennas in all the bandwidth used and its response to input pulses. With this objective, some analysis tools for antennas in the time domain have been developed. These tools provided and explanation to the radiation mechanism of some antennas. Through the use of large structures with respect to the duration of the input pulse it is possible to identify how the pulse propagates and how it is reflected by the structure. The relationship between the pulse position and the radiation of the antenna is then established for every position. This procedure enables the identification of the relationship between the antenna impulse response and the acceleration of charges in the structure. Finally, we present some results related to the performance of the antenna such as dispersion, distortion and normalized energy radiation pattern.

Antenna systems play a significant role in today’s electronic communications. They are essential for cell phones, satellites, radio, and radar among many other important applications. This paper describes the design, assembly, and operation of an antenna demonstration system designed to instill interest in the field of antenna design among high school and undergraduate college students. The system is portable, supplied solely by DC power supplies, easily reproducible, and includes rotational axes to illustrate antenna performance limitations and requirements. It provides a visual indication of wireless signal strength and demonstrates several antenna performance characteristics including polarization, gain and directivity, radiation patterns - nulls and maximums, and spreading loss. Several antenna types used in present-day applications (embedded and reflector antennas), in addition to structural barriers encountered in typical operating environments, are used to define wireless system performance. Students gain insight on radiating structure and orientation effects on antenna system characteristics and hopefully develop interest in future wireless studies.

Thesis (M.S.)--Ohio State University, 2006. / Includes bibliographical references (leaves 98-90). Available online via OhioLINK's ETD Center

Thesis (Ph.D.)--City University of Hong Kong, 2006. / "Submitted to Department of Electronic Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy" Includes bibliographical references (leaves 179-189)

<p>The demand for higher bit rates to support new services and more users is pushing wireless systems to millimetre-wave frequency bands with more available bandwidth and less interference. However at these frequencies, antenna dimensions are dramatically reduced complicating the fabrication process. Conductor loss is also significant, reducing the efficiency and gain of fabricated metallic antennas. To better utilize millimetre-wave frequencies for wireless applications, antennas with simple fabrication, higher efficiency, and larger impedance bandwidth are required.</p> <p>Dielectric Resonator Antennas (DRAs) offer many appealing features such as large impedance bandwidth and high radiation efficiency due to the lack of conductor and surface wave losses. DRAs also provide design flexibility and versatility. Different radiation patterns can be achieved by different geometries or resonance modes, wideband or compact antennas can be provided by different dielectric constants, and DRAs can be excited by a wide variety of feeding structures. Nevertheless, compared to their metallic counterparts, fabrication of DRAs is challenging since they have traditionally been made of high permittivity ceramics, which are naturally hard and extremely difficult to machine and cannot be easily made in an automatic way. The fabrication of these three dimensional structures is even more difficult at millimetre-wave frequencies where the size of the antenna is reduced to the millimetre or sub-millimetre range, and tolerances to common manufacturing imperfections are even smaller. These fabrication problems restrict the wide use of DRAs, especially for high volume commercial applications.</p> <p>A new approach to utilize the superior features of DRAs for commercial applications, introduced in this thesis, is to exploit polymer-based resonator antennas (PRAs), which dramatically simplifies fabrication due to the natural softness and results in a wide impedance bandwidth due to the low permittivity of polymers. Numerous polymer types with exceptional characteristics can be used to fulfill the requirements of particular applications or achieve extraordinary benefits. For instance, in this thesis photoresist polymers facilitate the fabrication of PRAs using lithographic processes. Another advantage derived from this approach is the capability of mixing polymers with a wide variety of fillers to produce composite materials with improved or extraordinary characteristics.</p> <p>The key contributions of this thesis are in introducing SU-8 photoresist as a radiating material, developing three lithographic methods to fabricate photoresist-ceramic composite structures, introducing a simple and non-destructive measurement method to define electrical properties of the photoresist composites, and demonstrating these structures as improved antenna components.</p> <p>It is shown that pure SU-8 resonators can be highly efficient antennas with wideband characteristics. To achieve more advantages for RF applications, the microwave properties of photoresists are modified by producing ceramic composite materials. X-ray lithography fabrication is optimized and as a result one direct and two indirect methods are proposed to pattern ultra thick (up to 2.3 mm) structures and complicated shapes with an aspect ratio as high as 36:1. To measure the permittivity and loss tangent of the resulting materials, a modified ring resonator technique in one-layer and two-layer microstrip configurations is developed. This method eliminates the requirement to metalize the samples and enables characterization of permittivity and dielectric loss in a wide frequency range from 2 to 40 GHz. Various composite PRAs with new designs (e.g. frame-based and strip-fed structures) are lithographically fabricated, tested, and discussed. The prototype antennas offer -10 dB bandwidths as large as 50% and gain in the range of 5 dBi.