Antenna Engineering Handbook, 4th Edition.pdf

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Part 1 - Introduction and Fundamentals

1 Fundamentals of Antennas, Arrays, and Mobile Communications

2 Frequency Bandsfor Military and Commercial Applications

3 Arrays of Discrete Elements

Part 2 - Types and Design Methods

4 Dipoles and Monopoles

5 Loop Antennas

6 Small Antennas

7 Microstrip Antennas

8 Slot Antennas

9 Waveguide Slot Antenna Arrays

10 Surface-Wave Antennas*

11 Leaky-Wave Antennas

12 Helical Antennas

13 Frequency Independent Antennas

14 Horn Antennas

15 Reflector Antennas

16 Wideband Microstrip Antennas

17 Dielectric Resonator Antennas

18 Lens Antennas

19 Ultrawide Bandwidth Antenna Design

20 Phased Arrays

21 Array Phase Shifters: Theory and Technology

22 Conformal and Low-Profile Arrays

23 Millimeter-Wave and Terahertz Antennas

24 Ultra Wideband Arrays

25 Smart Antennas

26 Methods of Polarization Synthesis

Part 3 - Applications

27 Low- and Medium-Frequency Antennas

28 HF Antennas

29 VHF and UHF Antennas for Communications and Broadcasting

30 Portable TV Antennas

31 Reconfigurable Antennas

32 Active Antennas

33 Fractal Antennas

34 Low Profile Antenna Performance Enhancement Utilizing Engineered Electromagnetic Materials

35 Reflectarray Antennas

36 Mobile Handset Antennas

37 Broadband Planar Antennas for High-Speed Wireless Communications

38 Antennas for Medical Applications

39 Automobile Antennas

40 Aircraft Antennas

41 Radiometer Antennas

42 Antenna Tracking

43 Microwave Beacon Antennas

44 Satellite Antennas

45 Earth Station Antennas

46 Seeker Antennas

47 Direction Finding Antennas and Systems

48 ESM and ECM Antennas

49 Radio-Telescope Antennas

50 Indoor Antenna Measurements

Part 4 - Topics Associated with Antennas

51 Transmission Lines and Waveguides

52 Impedance Matching, Broadbanding, and Baluns

53 Radomes

54 Propagation

55 Materials and Design Data

56 Frequency Selective Surfaces

57 Propagation Models and Antennas for MIMO

58 Multipath Techniques for Handset/Terminal Antennas

59 Computational Electromagnetics for Antennas

Source: ANTENNA ENGINEERING HANDBOOK P ● A ● R ● T ● 1 Introduction and Fundamentals Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2007 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website.

Introduction and Fundamentals Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2007 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website.

Source: ANTENNA ENGINEERING HANDBOOK Chapter 1 Fundamentals of Antennas, Arrays, and Mobile Communications Thomas F. Eibert Universität Stuttgart John L. Volakis The Ohio State University CONTENTS 1.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4 1.2 HUYGENS’ AND EQUIVALENCE PRINCIPLES. . . . . . . . . . . . . . . . . . 1-5 1.3 HERTZIAN AND FITZGERALD ELEMENTARY RADIATORS . . . . . . . 1-7 1.4 FAR-FIELD ANTENNA PROPERTIES, POWER TRANSFER, AND RECIPROCITY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8 1.5 ANTENNAS AS ELECTROMAGNETIC CIRCUITS. . . . . . . . . . . . . . . 1-11 1.6 POLARIZATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-14 1.7 1.8 DIRECTIVITY PATTERNS FROM CONTINUOUS LINE SOURCES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-17 DIRECTIVITY PATTERNS FROM AREA SOURCE DISTRIBUTIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-21 1.9 FUNDAMENTALS OF ANTENNA ARRAYS . . . . . . . . . . . . . . . . . . . . 1-27 1.10 BASIC CONCEPTS IN MOBILE COMMUNICATIONS . . . . . . . . . . . 1-32 1-3 Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2007 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website.

Fundamentals of Antennas, Arrays, and Mobile Communications 1-4 CHAPTER ONE 1.1 INTRODUCTION * Antennas are key components of any wireless communication system.1,2 They are the devices that allow for the transfer of a signal (in a wired system) to waves that, in turn, propagate through space and can be received by another antenna. The receiving antenna is responsible for the reciprocal process, i.e., that of turning an electromagnetic wave into a signal or voltage at its terminals that can subsequently be processed by the receiver. The receiving and transmitting functionalities of the antenna structure itself are fully char- acterized by Maxwell’s equations and are fairly well understood.3 The dipole antenna (a straight wire, fed at the center by a two-wire transmission line) was the first antenna ever used and is also one of the best understood.1,2 For effective reception and transmission, it must be approximately l/2 long (l = wavelength) at the frequency of operation (or multiples of this length). Thus, it must be fairly long (or high) when used at low frequencies (l = 1 m at 300 MHz), and even at higher frequencies (UHF and greater), its protruding nature makes it quite undesirable. Further, its low gain (2.15 dB), lack of directionality, and extremely narrow bandwidth make it even less attractive. Not surprisingly, the Yagi-Uda antenna (typically seen on the roof of most houses for television reception) was considered a breakthrough in antenna technology when introduced in the early 1920s because of its much higher gain of 8–14 dB. Log-periodic wire antennas introduced in the late 1950s and 1960s and wire spirals allowed for both gain and bandwidth increases. On the other hand, even today high gain antennas rely on large reflectors (dish antennas) and waveguide arrays (used for many radar systems). Until the late 1970s, antenna design was based primarily on practical approaches using off-the-shelf antennas such as various wire geometries (dipoles, Yagi-Uda, log-periodics, spirals), horns, reflectors, and slots/apertures as well as arrays of some of these. The antenna engineer could choose or modify one of them based on design requirements that characterize antennas, such as gain, input impedance, bandwidth, pattern beamwidth, and sidelobe levels (see References 4 and 5 for a description of these quantities). Antenna development required extensive testing and experimentation and was, therefore, funded primarily by governments. However, in recent years, dramatic growth in computing speed and develop- ment of effective computational techniques for realistic antenna geometries has allowed for low-cost virtual antenna design. Undoubtedly, the explosive growth of wireless communi- cations and microwave sensors, microwave imaging needs, and radars has been the catalyst for introducing a multitude of new antenna designs over the past decade and an insatiable desire for using modern computational techniques for low-cost designs. Requirements for ∗Heinrich R. Hertz was the first to demonstrate the generation of radio waves at UHF using a gap dipole in 1885– 1886 at Karlsruhe University (Germany). Hertz was able to detect radio waves 20 m away using a high-voltage electrical spark discharge to excite the dipole gap. From recorded conversations, Hertz did not seem to understand the impact of his experiments, but instead did it as a validation of the newly developed Maxwell’s equations. Within ten years, Tesla at the Franklin Institute in the U.S., Marconi in Bologna, Italy, Popov in Russia, and Bose in India, demonstrated wireless telegraphy. In 1892, Tesla delivered a widely distributed presentation at the IRE of London about “transmitting intelligence without wires,” and in 1895, he transmitted signals detected 50 miles (80 km) away. Concurrently, in 1894 Bose used wireless signals to ring a bell in Calcutta, and Popov presented his radio receiver to the Russian Physical & Chemical Society on May 7, 1895. Marconi is certainly considered the key individual for his contributions to the commercialization of radio waves, and he received the Nobel prize for his work in 1909. Nevertheless, Marconi’s widely advertised first radio wave transmission experiment was in 1895, and his British pat- ent application in 1897 was preceded by that of Tesla. A culmination of Marconi’s experiments was the December 12, 1901, trans-Atlantic radio wave transmission of the Morse code for the letter S. The success of this experiment is often disputed, possibly due to strong atmospheric noise during the time of the experiment, but by the 1920s the U.S. had hundreds of radio stations, and in 1922, the BBC began transmitting in England. Subsequent development of radio detectors, vacuum tubes, and the tiny transistor in 1947 played a critical role in the practical everyday use of radio waves for communication and wireless transmission of information. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2007 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website.

Fundamentals of Antennas, Arrays, and Mobile Communications FUNDAMENTALS OF ANTENNAS, ARRAYS, AND MOBILE COMMUNICATIONS 1-5 conformal antennas (non-protruding) for airborne systems, increased bandwidth require- ments, and multifunctionality have led to heavy exploitation of printed (patch) or other slot-type antennas4 and the use of powerful computational tools (commercial and noncom- mercial) for designing such antennas. Needless to say, the commercial mobile communications industry has been the catalyst for the recent explosive growth in antenna design needs. Certainly, the past decade has seen an extensive use of antennas by the public for cellular, GPS, satellite, wireless LAN for computers (WiFi), Bluetooth technology, Radio Frequency ID (RFID) devices, WiMAX, and so on. However, future needs will be even greater when a multitude of antennas are integrated into say automobiles for all sorts of communication needs and into a variety of portable devices and sensors for monitoring and information gathering. Certainly, future RFID devices will most likely replace the bar codes on all products while concurrently allowing for instantaneous inventorying. For military applications, there is an increasing need for small and conformal multifunctional antennas that can satisfy a plethora of com- munications needs using as little space as possible. In this first chapter of the handbook, we provide a summary of antenna fundamen- tals and introduce antenna parameters typically used for characterizing antenna properties often employed to evaluate the entire radio system. We start with the radiation of an ideal (Hertzian) or infinitesimal dipole and proceed to the resonant l/2 dipole, antenna arrays, and mobile communication concepts. 1.2 HUYGENS’ AND EQUIVALENCE PRINCIPLES The electromagnetic behavior and thus the functioning of antennas is governed by Maxwell’s equations,3 which must be solved for a particular antenna and a given excita- tion. Typically, exact solutions of Maxwell’s equations are not available and thus numerical modeling is often used to compute approximate solutions for practical configurations. A formal simplification of electromagnetic antenna problems can be achieved by employing the equivalence principle.3 If interest is restricted to the field solution in a limited region of space, the antenna configuration can be replaced by the equivalent electromagnetic sources located on the surface of a volume enclosing the antenna configuration (see Figure 1-1). Because the antenna materials are no longer there, these sources are usually radiating in a homogeneous solution space (such as free-space), and the corresponding fields can thus be calculated by evaluating the radiation integrals. The equivalent sources are not uniquely defined, and there are many different ways of constructing them. In general, the equivalent sources are a composition of electric and mag- netic surface current densities representing the excitation terms in Maxwell’s equations. A straightforward way of constructing equivalent sources is provided by Huygens’ principle.3 Huygens’ principle states that the field solution in a region V is completely determined by the tangential fields over the surface S enclosing V. The corresponding electric and mag- netic equivalent surface current densities are given by Electric current density: Magnetic current density: J = ˆn × H M = − ×ˆn E (1-1) (1-2) Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2007 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website.

Fundamentals of Antennas, Arrays, and Mobile Communications 1-6 CHAPTER ONE n S R = r − r r M z y J r x FIGURE 1-1 Replacement of an antenna by equivalent elec- tric and magnetic surface current densities where both J and H are expressed in amperes per meter (A/m) and M and E are expressed in volts per meter (V/m). For the problem of a radiating antenna, as illustrated in Figure 1-1, the outer boundary of V is assumed to be located at infinity, where the fields radiated by the corresponding equivalent sources can be neglected. As shown in the figure, the antenna can be replaced by equivalent sources on an arbitrary surface S enclosing it. As already mentioned, these equivalent sources reproduce the radiated fields of the antenna, and they can be assumed as radiating in homogeneous space. For a particular antenna configuration, the exact determination of J and M requires knowledge of the true field distribution on S. However, for many practical antennas, an approximate determination of J and M is pos- sible. For instance, placing S to coincide with a metallic section of the antenna structure causes M to vanish on these portions of S. The radiated fields from any antenna can be obtained by integrating the field contribu- tions of the equivalent electric and magnetic current densities using the well-known radia- tion integral:3 E = − ωµ j 0  J   ∫∫  S r ( ') − j e k π | 4 r-r | '| 0 r - r + ' | 1 2 k 0 ( ∇ ⋅ ' J r ( '')) ∇ − e π 4 '| r-r | j 0 k r - r |    ' | ds ' + ∫∫ M r ( ') × ∇ −e r-r '| | r - rπ 4 kj 0 | ' | ds ' which for the far-field (r → ∞) reduces to (see Figure 1-1) E = − where j k r 0 − e ωµ π j 4 r 0 ∫∫    (   I − ˆˆ) rr ⋅ J r ( ') − ε 0 µ 0 ˆ r × M r   ( ')   krj ˆ ⋅ r ' e ds ' I = unit dyad r = defines location of observation point (see Figure 1-1) r = distance (in m) to observation point r' = defines location of the integrated surface current densities ˆr = unit vector in radial direction e0 = free-space permittivity m0 = free-space permeability Z0 = µ 0 ε 0 = free-space impedance Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2007 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website.

Fundamentals of Antennas, Arrays, and Mobile Communications FUNDAMENTALS OF ANTENNAS, ARRAYS, AND MOBILE COMMUNICATIONS 1-7 0 =ωµ 0 k Z0 k0 = b = 2p /l l = wavelength (in meters, m) j = −1 E is given in volts per meter (V/m) H is given in amperes per meter (A/m) For the ideal (delta) or infinitesimal electric (Hertzian) or magnetic (Fitzgerald) dipole sources, the radiation integrals are eliminated and the fields can be given in closed forms. The resulting field expressions can then be used to extract and study the usual antenna parameters. 1.3 HERTZIAN AND FITZGERALD ELEMENTARY RADIATORS Considering the infinitesimal electric dipole J = ˆz Idz (z)δ , as illustrated in Figure 1-2, the resulting rms (root mean square) electric and magnetic field components are given by r = E k 2 0 µ Idz 0 ε π 2 0 E θ = j k 2 0 µ Idz 0 ε π 4 0 (         1 k r 0 2 ) − j k r 0 ( 3 )     cos θ e −− j k r 0 , 1 k r 0 − j k r 0 ( 2 ) − 1 k r 0 ( 3 )     sin − jθ e k r0 H φ = j k 2 0 Idz π 4     1 k r 0 − j k r 0 ( )22     E φ = H r = H θ = 0 where sin jθ e k r 0 , (1-3) , Idz = moment of the differential current element ( I is given in rms amperes, and dz is given in meters) FIGURE 1-2 Coordinate system for an electric dipole Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2007 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website.

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