Efficiency characterisation of multi-port antennas

A simple radiation efficiency metric is introduced to include the effects of non-ideal source/receiver impedances. The features of this parameter are highlighted and its compact formula is derived. The notion of mean matching efficiency is established. Simulations prove that this matching efficiency is quite useful in a quick estimation of diversity performance of multi-port antennas in rich isotropic multipath environments

Multi-port matching efficiency in antenna systems with cascaded networks

A general compact formula for multi-port matching efficiency in the presence of an arbitrary number of cascaded networks is introduced. A comparison between the decoupling efficiency and multi-port matching efficiency is presented. Similarly, a compact formula for decoupling efficiency in a cascaded chain is provided. The presented compact formulas are quite advantageous for optimization of radiation efficiencies by designing a proper matching network

Spatial Characterization of Multi-element Antennas

The overall goal of the current thesis is to establish some bases for understanding and characterization of multi-port antennas in a rich multipath environment. Multi-port antennas are the inevitable keystone of multiple input and multiple output wireless communication systems. Due to multidisciplinary nature of the applications of multi-element antennas, they are the subjects of many research groups worldwide resulting in inconsistent nomenclature among them. In this thesis, much effort is expended to look upon this realm of engineering in a unifying approach, with the major stress on electromagnetic aspects of this area. The thesis throws light upon different significant parameters as the key-gauges for characterization of multi-port antennas. We illustrate the dependency of precise measurement of diversity gains upon total number of independent measured samples. Two closed-form formulas are devised rendering diversity gains of two-port antennas in a rich scattering environment. Some examples are presented to verify the accuracy of these formulas. Moreover, received signals at different ports of a multi-element antenna in a multipath environment are the major sources for its assessment. There are certain functions governing the relation between the received signals at different ports of a radiation system and an arbitrary incident electromagnetic wave. The precise derivation of these formulas for different cases of interest are presented in this thesis. Furthermore, it has been frequently acknowledged that in a uniform rich multipath environment the beam-forming technique does not prove beneficial. Here for the first time, we stress that in a uniform non-rich scattering environment, beam-forming technique bestows considerable gain. We demonstrate that the achieved gain in respect to a similar radiation system reduces as the multipath environment becomes richer. In addition to that, it is known that reverberation chambers are the contemporary measurement tools for antenna systems to be used in scattering environments. The shape of these measurement tools plays a significant role in their ultimate performance. We show that rectangular reverberation chambers prove to be more advantageous compared with their cylindrical and spherical counterparts

Beeinflussung des EMV-Grundrauschpegels durch oberirdische Kupferleitungen im Kontext von Breitbandnetzen

Der zunehmend umkämpfte Telekommunikationssektor erfordert von jedem Marktteilnehmer eindeutige Differenzierungsmerkmale. Dies, weil immer mehr Anbieter mit ähnlichen Produkten und Angeboten auf den Markt drängen und somit die Tarife stark unter Druck geraten. Nebst der Bedeutung von kundenorientiertem Service werden auch die Anforderungen an leistungsfähige Breitbandnetze eminent höher. Gerade neue Produkte und Telekomdienste, wie beispielsweise hochauflösendes Fernsehen, CloudDienste oder Videokonferenzen, fordern das bestehende Netz heraus. Durch diese Treiber sind neue Glasfaserhybrid Technologien entstanden, die auf den bestehenden Kupferleitungen aufbauen. Demnach wird dort, wo das Glasfasernetz nicht vorhanden ist, entsprechende neue Glasfaserhybrid Technologien ausgerollt (Spektrum von bis zu ca. 230 MHz). Swisscom plant eine Reihe von Messungen am aktiven Netz durchzuführen, um die Beeinflussung des EMV Grundrauschpegels zu untersuchen. Gleichzeitig werden auch Simulationen an der gleichen Geometrie durchgeführt, um die Korrelation zwischen Simulation und Berechnungen nachzuweisen. Für die Durchführung solcher Messungen gibt es keinen Standard, daher muss ein Kompromiss zwischen Messgeschwindigkeit, Qualität der Resultate und Auflösung getroffen werden

Design and Measurement-Based Evaluation of Multi-Antenna Mobile Terminals for LTE 3500 MHz Band

Design of multi-element antennas for small mobile terminals operating at higher frequencies remains challenging despite smaller antenna dimension and possibility of achieving electrically large separation between them. In this paper, the importance of the type of radiating elements operating at 3400-3600 MHz and their locations on the terminal chassis are highlighted. An isotropic radiation pattern that receives incoming signals from arbitrary directions is obtained by combining the radiation patterns of multiple antennas with localized chassis current distribution. Four multiport antennas configurations with two- and eight-element antennas are designed and evaluated experimentally in indoor propagation environments. Our proposed designs of multi-element antennas provide the highest MIMO channel capacity compared to their counterparts using antennas with less localized chassis current distribution, even in the presence of user's hand

A novel waveguide design for traveling-wave electroabsorption modulators

The overall goal of the current thesis addresses the configuration of the waveguide used in Traveling-wave Optical Modulators. In general, our concerns affiliate mostly with achievement of high confinement factor, improved coupling efficiencies and finally single-mode propagation. In principle, waveguides for optical modulators are quite difficult to design entirely, and the usual, and perhaps the most fruitful, approach is to incorporate or slightly modify one of the existing designs. In this sense, we base our structure on the available waveguide, which was already realized in the department, and introduce two etched channels in either side of the mesa structure. From technological point of view, the mentioned fact guarantees the robustness of the novel waveguide for implementation purposes. Meanwhile, we restrict our modifications in a way not to violate the plausible properties of the available guides rather to enhance them more to meet our further expectations. We show that both confinement factor and coupling efficiency can enhance considerably by virtue of these etched channels. Also, it is shown that the novel design renders single-mode propagation structure

Comparative Study of Different Excitation Techniques for Microstrip-like Structures over an Infinite Perfect Electric Conductor Plane

The overall goal of the thesis is to establish detailed comparisons among different well-known models of excitations in their application on Microstrip-like Monopoles. Comparisons are made over the input impedances predicted by these excitations. In this way, the Galerkin’s version of the Method of Moment is applied and rooftops functions are chosen as our basis/weighting functions. Different excitation models have their influence over the excitation vector and a unique MoM matrix is used to give input impedances. We shall elicit the effects of several parameters over relative input self/mutual impedances derived from these excitation models and finally make conclusions about their differences in anticipating the input Resistance, input Reactance and also resonance frequencies

Multiport Antenna Systems for Space-Time Wireless Communications

Multiport antenna systems are indispensable part of modern wireless communication systems. Their crucial impact on the overall performance requires sufficient regard and dedication to a precise design and characterisation. This concern has been to a considerable extent addressed in the frame of the current thesis. The thesis starts by a brief review of the evolution on wireless communication systems. In particular, the role of multiport antennas in modern communication systems is highlighted. The multidisciplinary nature of multiport radiation terminals makes them the subject of many research groups worldwide, resulting in inconsistent nomenclature. Thus, a few words are dedicated to throwing light upon some important metrics in this discipline. The notion of richness threshold as a further crucial performance metric is introduced. The importance of the latter parameter is emphasised by virtue of some practical examples. We describe how an RF Butler network can be used to remarkably enhance the performance of spatial diversity systems. Subsequently, the advantage of a predictor antenna system in modern moving relays is underlined. We illustrate and quantify how the coupling removal can improve the prediction capability of this system. This can be most conveniently carried out through signal processing, amplifying the prediction reliability. To verify the foregoing achievement, some results associated with measurements in actual scenarios are presented. Moreover, a quick and inexpensive measurement of antennas in multipath environments is of foremost concern for antenna system designers. This issue is simply possible by reverberation chamber technologies. We briefly clarify how further analysis can be utilised to facilitate measurements in these chambers. At the end, we devote a short discussion to some state-of-the-art antenna designs which are suitable for the modern compact mobile terminals, manifesting certain rewarding features

Spatial Characterization of Multi-element Antennas

The overall goal of the current thesis is to establish some bases for understanding and characterization of multi-port antennas in a rich multipath environment. Multi-port antennas are the inevitable keystone of multiple input and multiple output wireless communication systems. Due to multidisciplinary nature of the applications of multi-element antennas, they are the subjects of many research groups worldwide resulting in inconsistent nomenclature among them. In this thesis, much effort is expended to look upon this realm of engineering in a unifying approach, with the major stress on electromagnetic aspects of this area. The thesis throws light upon different significant parameters as the key-gauges for characterization of multi-port antennas. We illustrate the dependency of precise measurement of diversity gains upon total number of independent measured samples. Two closed-form formulas are devised rendering diversity gains of two-port antennas in a rich scattering environment. Some examples are presented to verify the accuracy of these formulas. Moreover, received signals at different ports of a multi-element antenna in a multipath environment are the major sources for its assessment. There are certain functions governing the relation between the received signals at different ports of a radiation system and an arbitrary incident electromagnetic wave. The precise derivation of these formulas for different cases of interest are presented in this thesis. Furthermore, it has been frequently acknowledged that in a uniform rich multipath environment the beam-forming technique does not prove beneficial. Here for the first time, we stress that in a uniform non-rich scattering environment, beam-forming technique bestows considerable gain. We demonstrate that the achieved gain in respect to a similar radiation system reduces as the multipath environment becomes richer. In addition to that, it is known that reverberation chambers are the contemporary measurement tools for antenna systems to be used in scattering environments. The shape of these measurement tools plays a significant role in their ultimate performance. We show that rectangular reverberation chambers prove to be more advantageous compared with their cylindrical and spherical counterparts

Multiport Antenna Systems for Space-Time Wireless Communications

Multiport antenna systems are indispensable part of modern wireless communication systems. Their crucial impact on the overall performance requires sufficient regard and dedication to a precise design and characterisation. This concern has been to a considerable extent addressed in the frame of the current thesis. The thesis starts by a brief review of the evolution on wireless communication systems. In particular, the role of multiport antennas in modern communication systems is highlighted. The multidisciplinary nature of multiport radiation terminals makes them the subject of many research groups worldwide, resulting in inconsistent nomenclature. Thus, a few words are dedicated to throwing light upon some important metrics in this discipline. The notion of richness threshold as a further crucial performance metric is introduced. The importance of the latter parameter is emphasised by virtue of some practical examples. We describe how an RF Butler network can be used to remarkably enhance the performance of spatial diversity systems. Subsequently, the advantage of a predictor antenna system in modern moving relays is underlined. We illustrate and quantify how the coupling removal can improve the prediction capability of this system. This can be most conveniently carried out through signal processing, amplifying the prediction reliability. To verify the foregoing achievement, some results associated with measurements in actual scenarios are presented. Moreover, a quick and inexpensive measurement of antennas in multipath environments is of foremost concern for antenna system designers. This issue is simply possible by reverberation chamber technologies. We briefly clarify how further analysis can be utilised to facilitate measurements in these chambers. At the end, we devote a short discussion to some state-of-the-art antenna designs which are suitable for the modern compact mobile terminals, manifesting certain rewarding features