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Spie Press Book

Fundamentals of Antennas: Concepts and Applications
Author(s): Christos G. Christodoulou; Parveen Wahid
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Book Description

This tutorial explains antenna design and application for various systems, including communications, remote sensing, radar, and biomedicine. It describes basic wire and array antennas in detail and introduces other types such as reflectors, lenses, horns, Yagi, microstrip, and frequency-independent antennas. Integration issues and technical challenges are discussed. Aimed at students, engineers, researchers, and technical professionals.

Book Details

Date Published: 1 September 2001
Pages: 106
ISBN: 9780819441126
Volume: TT50

Table of Contents
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Preface
Chapter 1 History and Applications
1.1 History and development of antennas
1.2 Applications and impact on systems
1.2.1 Antennas in communication systems
1.2.2 Antennas in remote sensing
1.2.3 Antennas for biomedical applications
1.2.4 Radio astronomy applications
1.2.5 Radar antennas
References
Chapter 2 Fundamental Parameters of Antennas
2.1 Radiation pattern
2.2 Power density
2.3 Radiation intensity
2.4 Directivity
2.5 Gain
2.6 Input impedance
2.7 Bandwidth
2.8 Polarization
2.9 Friis formula
References
Chapter 3 Wire Antennas
3.1 Infinitesimal dipoles
3.1.1 Directivity
3.2 Small dipole
3.3 Dipole of finite length
3.3.1 Input impedance
3.4 Effect of infinite conductors on the radiation pattern of linear wire antennas
3.5 Loop antennas
3.5.1 Small circular loop antennas
3.5.2 Large circular-loop antennas
3.6 Radiated fields of a short dipole and a small loop
References
Chapter 4 Antenna Arrays
4.1 Array factors
4.2 Uniform N-element linear array
4.2.1 Broadside array
4.2.2 End-fire array
4.3 Planar arrays
4.4 Circular arrays
References
Chapter 5 Types of Antennas
5.1 Reflector antennas
5.1.1 Plane and corner reflectors
5.1.2.Parabolic reflector
5.2 Lens antenna
5.3 Horn antennas
5.4 Microstrip antennas
5.4.1 Analysis of microstrip antennas
5.4.2 Multiple feeds for circular polarization
5.4.3 Microstrip Arrays
5.5 Radome Coverings
References
Chapter 6 Antennas for Infrared Detectors
6.1 Antennas for infrared detectors
6.2 Design of helical antennas for terahertz applications
6.3 Design of Broadband FIR antennas
References
Chapter 7 Antenna Measurements
7.1 Radiation pattern measurements
7.1.1. Outdoor Ranges
7.1.2 Anechoic Chambers
7.2 Gain measurements
7.2.1 Comparison method
7.2.2 Two-Antenna method
7.3 Impedance measurements
References
Index

Preface

The field of information science and technology incorporates several devices, including antennas, which can be used to transmit, collect and transfer information. Understanding how these antennas work and how they can be utilized at different frequencies ranging from radio to terahertz requires some insight into the physics of antenna operation and a knowledge of the basic parameters for their operation. This book, which is tutorial in nature, contains seven chapters. Chapter 1 outlines how antennas have evolved historically, and presents some important advances made in their design and applications. The chapter discusses the impact of antennas in various systems, to give the reader an idea of the range of their applications that include communications, remote sensing, radar, biomedicine, etc. In Chapter 2 the reader is introduced to the fundamentals of antennas. All of the figures of merit and parameters used to evaluate antennas are covered. Concepts such as radiation pattern, directivity, gain, bandwidth, polarization, and others are explained in a very straightforward manner. The information provided in this chapter forms the cornerstone upon which all other chapters are built.

Chapter 3 introduces the most basic type of antenna, the wire antenna, and presents the analysis of this antenna for different configurations such as small dipoles, dipoles of finite length, and loop antennas. These antennas are still used today in a variety of applications such as communication, TV broadcasting, and navigation. In Chapter 4, array antennas are discussed. Several antennas can be arranged in space, in different geometrical configurations, to produce a highly directional pattern . Such a configuration of multiple antenna elements is referred to as an antenna array. In an array antenna, the fields from the individual elements can be made to interfere constructively in some directions and cancel in others. Phased array antennas offer the unique capability of scanning of the main beam (major lobe) by changing the phase of the excitation of each array element.

Chapter 5 exposes the reader to a variety of antennas, such as reflectors, lenses, horns, and microstrip antennas. This chapter adds to the knowledge base provided by the previous chapters by explaining how different applications require different antennas and why a single antenna cannot be used successfully for all applications. Chapter 6 shows how an antenna can be integrated with a detector for successful operation in order to efficiently collect terahertz radiation. These integrated antennas have several applications in areas such as remote sensing, radio astronomy, plasma diagnostics, atmospheric studies, and space communications. However, these applications demand the use of low-noise receivers over a range of about 30 GHz to more than 1 THz. The serious technical challenges on the design and use of submillimeter-wave local oscillators and detectors that exist are presented and discussed in this chapter, which is a fusion between optics and antenna concepts. In Chapter 7, antenna measurements techniques are described. Measurements often form an integral part of the antenna design process, with measurements on prototype antennas being conducted at various steps of the design process to check that the antenna meets the design specification. The key parameters that are often measured are the radiation pattern, efficiency, gain, and impedance. Depending on the antenna and its application, other parameters such as the polarization purity, power-handling capacity, etc., may also be measured. The use of sophisticated computerized equipment has made it possible to make accurate measurements of antenna parameters. The advantages and disadvantages of performing measurements indoors using anechoic chambers versus outdoors ranges are presented and discussed as well. This book is intended for students, engineers, and researchers who have not taken a formal antenna course and are interested in the basics of antenna theory and operation. The authors have attempted to link the lower-frequency (RF) concepts to the higher-frequency (optics) concepts with which the readers may be more familiar. The book is written in a modular fashion, so the readers can choose the chapters they are interested in without having to go through the entire book. It is the hope of the authors that the readers find in this book the necessary tools and examples that can help them in incorporating antennas, as needed, in their research problems.


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