Orthogonal Methods for Array Synthesis: Theory and the ORAMA Computer Tool - Hardcover

Sahalos, John

Hardcover

ISBN 10: 0470017414 ISBN 13: 9780470017418

Verlag: Wiley, 2006

Inhaltsangabe

The first time that such a complete systematic analysis of the mathematical and numerical techniques related to the orthogonal methods has been given.
 
With the explosion of the wireless world, greater emphasis than ever before is being placed on the effective design of antennas. Orthogonal Methods for Array Synthesis outlines several procedures of orthogonal methods suitable for antenna array synthesis. The book presents a simple approach to the design of antenna arrays to enable the reader to use the classical Orthogonal Method for synthesis of linear arrays.
 
This theory-based book, which includes rapid, effective solutions to design problems for communications applications and broadcasting, is amply illustrated with real-world examples and case studies. Also included in the book is the ORAMA MS Windows-compatible computer tool, patented by Professor Sahalos and his team.
* Provides comprehensive coverage of the basic principles of orthogonal methods including an analytical explanation of the orthogonal method (OM) and the orthogonal perturbation method (OP)
* Gives rapid, cost-effective solutions to antenna design problems for communications applications and broadcasting
* Illustrates all theory with practical applications gleaned from the author's extensive experience in the field of orthogonal advanced methods for antennas
 
Providing a complete guide to the theory and applications of the Orthogonal Methods, this book is a must-read for antenna engineers and graduate students of electrical and computer engineering and physics.

Über diesen Titel

Über die Autorin bzw. den Autor

Professor John N. Sahalos is a professional engineer and consultant to industry and Head of the Radio Communications Laboratory, Department of Physics, University of Thessaloniki, Greece. He is a member of the New York Academy of Science and the Technical Chamber of Greece. In 2002, he was appointed to serve a five-year term on the Board of Directors of the Hellenic Telecommunications Organization S.A. His research interests are in the areas of applied electromagnetics, antennas, high frequency methods, communications, microwaves and biomedical engineering.

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The first time that such a complete systematic analysis of the mathematical and numerical techniques related to the orthogonal methods has been given.

With the explosion of the wireless world, greater emphasis than ever before is being placed on the effective design of antennas. Orthogonal Methods for Array Synthesis outlines several procedures of orthogonal methods suitable for antenna array synthesis. The book presents a simple approach to the design of antenna arrays to enable the reader to use the classical Orthogonal Method for synthesis of linear arrays.

This theory-based book, which includes rapid, effective solutions to design problems for communications applications and broadcasting, is amply illustrated with real-world examples and case studies. Also included in the book is the ORAMA MS Windows-compatible computer tool, patented by Professor Sahalos and his team.

• Provides comprehensive coverage of the basic principles of orthogonal methods including an analytical explanation of the orthogonal method (OM) and the orthogonal perturbation method (OP)
• Gives rapid, cost-effective solutions to antenna design problems for communications applications and broadcasting
• Illustrates all theory with practical applications gleaned from the author’s extensive experience in the field of orthogonal advanced methods for antennas

Providing a complete guide to the theory and applications of the Orthogonal Methods, this book is a must-read for antenna engineers and graduate students of electrical and computer engineering and physics.

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Orthogonal Methods for Array Synthesis

Theory and the ORAMA Computer ToolBy John N. Sahalos

John Wiley & Sons

Copyright © 2006 John Wiley & Sons, Ltd
All right reserved.
ISBN: 978-0-470-01741-8

Chapter One

Antennas and Antenna Arrays

1.1 Introduction

Antennas have become ubiquitous devices and occupy a salient position in wireless systems. Radio and TV as well as satellite and new generation mobile communications have experienced the largest growth among industry systems. The global wireless market continues to grow at breakneck speed and the strongest economic and social impact nowadays comes from cellular telephony, personal communications and satellite navigation systems. All of the above systems have served as motivation for engineers to incorporate elegant antennas into handy and portable systems.

Many textbooks provide in-depth resources on antennas. Especially on antenna arrays, there are digests, studies and books containing extensive data and techniques. In the references given herewith, there are some of the best-known and most highly recommended books.

A device able to receive or transmit electromagnetic energy is called an 'antenna'. As seen in [6], the antenna plays the role of a transitional structure between free space and a guiding device. An antenna consists of one or more elements. A single-element antenna is usually not enough to achieve technical needs. That happens because its performance is limited. A set of discrete elements, which constitute an antenna array, offers the solution to the transmission and/or reception of electromagnetic energy. The geometry and the type of elements characterize an antenna array. For simplicity, implementation and fabrication reasons, the elements are chosen in such a way so as to be identical and parallel. For the same reasons, uniformly spaced linear arrays are mostly encountered in practice.

In the following paragraphs, the properties of various antenna arrays will be presented.

1.2 Antenna Array Factor

The radiation characteristics of antennas have mostly to do with the far field (Fraunhofer) region. In this region, the field expression is a multiplication of two parts. One part contains the distance r dependence of the observation point (receiver location) and the other contains its spherical coordinate angles θ and φ dependence. The angular distribution of the field is independent of the distance r. For a typical antenna element (see Fig. 1.1), the far electric field is

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (1-1)

The angular-dependent vector f_n(θ, φ) gives the directional characteristics of the nth element electric field [11]:

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (1-2)

where

J_n(r'_n) = electric current density of the nth element

r'_n = distance of a source point from the origin

r = distance of the observation point from the origin

ß = 2π/λ the free space wave number

ω = the angular frequency and

µ = the magnetic permeability of the space

The total electric field of an N element antenna array is

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (1-3)

Moreover, the total magnetic field is,

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (1-4)

where η = √µ/[member of] ([member of] is the electric permeability of the space).

For identical and identically oriented elements, the current distribution of each element is approximately the same except for a constant complex multiplier. In (1-1), f_n(θ, φ) can be expressed as

f_n(θ, φ) = I_n f(θ, φ) (1-5)

f (θ, φ) is called the 'pattern function' of the element and I_n is the complex excitation of the nth element of the array.

(1-1), (1-2) and (1-5) are combined and give

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (1-6)

(r_n, θ_n, φ_n) are the spherical coordinates of a convenient reference point of the nth element and cos ξ_n = sin θ sin θ_n cos(φ - φ_n) + cos θ cos &theta_n.

The last term of (1-6) is expressed separately as

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]

AF(θ, φ) is called the 'array factor'. This factor is actually the array pattern of N isotropic point sources positioned at the reference points of the elements of the original array.

From (1-6) and (1-7), we have the following:

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (1-8)

Expression (1-8) states the following pattern multiplication principle: An array consisting of identical and identically oriented elements has a pattern, which can be expressed as the product of the element pattern and the array factor.

An antenna engineer has to make an anticipatory and compatible choice of elements according to technical requirements. Once the element pattern is derived, the design effort is mainly directed at the array factor.

1.3 Elements and Array Types

Element types of antenna arrays are delineated in the literature. Dipoles, monopoles, loops, slots, microstrip patches and horns are the most common types of array elements. Recent studies and innovations have resulted in new types of elements. Some of them are the monolithic, the superconducting, the active and the electronically and functionally small antenna elements.

In parallel with the development of elements, antenna arrays have experienced a tremendous growth. Their list starts with the linear broadside and end-fire arrays, the planar, the circular, and the conformal, and goes up to the adaptive arrays. Moreover, flat plate slot arrays, digital beam forming, dichroic, slotted and fractal arrays are some of the recent types.

It was mentioned previously that antenna analysis and synthesis focuses mostly on the array factor. Consequently, in the following paragraphs we devote the analysis mainly to this factor.

1.4 Antenna Parameters and Indices

In many cases, it is necessary to characterize the performance of antennas by referring to specific parameters and indices. Most of these parameters and indices have been defined by the committees of the institutions in charge (IEEE, ETSI etc.) and will be presented in this paragraph.

It is well known that antennas have to do with applications of time varying fields. Sources with e^jωt time variation produce fields that also vary in the same way. In the literature, the above fields are called 'time-harmonic fields'. If a signal with certain bandwidth is present in an antenna, the Fourier transform can derive the time varying forms of the electromagnetic quantities. The procedure is analogous to that of solving electric circuit problems. In this book, time-harmonic fields with a proper choice of working frequency/ies are assumed.

1.4.1 Radiated Power

The time average power density, which is the average Poynting vector, can be written in the following form:

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (1-9)

The 1/2 in (1-9) appears because the electric and magnetic fields represent the peak values.

The radiated power P_r, through a closed surface S surrounding the antenna, can be...

Details zur Ausgabe

• Verlag: Wiley
• Erscheinungsdatum: 2006
• Sprache: Englisch
• ISBN 10: 0470017414
• ISBN 13: 9780470017418
• Einband: Gebundene Ausgabe
• Auflage: 1
• Anzahl der Seiten: 228
• Kontakt zum Hersteller: Wiley-VCH GmbH; product_safety@wiley.com; ; Boschstrasse 12; Weinheim; 69469; Deutschland