The adapted edition is primarily intended as a textbook for the undergraduate students of Electronics and Communication Engineering, Electronics and Telecommunication Engineering and Electronics Engineer-ing. The subject of antennas is a compulsory course in fifth or sixth semesters of B.Tech. This book will also prove to be beneficial for postgraduate students of M.Tech and M.Sc. (Physics) who opt to study wave propagation, microwaves, communication systems, astronomy, remote sensing, etc.

For the study of antenna, the students should have a basic knowledge of the electromagnetic fields.

Salient FeatureS

Some of the salient features of this edition are: d Content presentation supports outcomes based learning approach d New chapter on Antennas for Mobile Communication d Revised chapters on Radiation and Microstrip Antennas d Rich pedagogy with more than 700 questions including solved examples, unsolved problems and

objective type questions from GATE examination d Many topics, viz. Yagi Antennas, dipole, monopole, short dipole, Hertzian dipole and Feed Methods

are now discussed in detail d Brief summary comprising some important definitions, terms etc. are given at the end of each chapter d Appendices include useful tables and references, programs and answers to objective type questions d Additional reading material and web links are provided on Online Learning Center

What iS neW in the FiFth edition

This edition is completely student-centric as it follows the ‘Learning Outcomes’ approach. It contains 23 chapters each containing a set of learning objectives.

Preface to the Adapted Fifth Edition

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xxii Preface to the Adapted Fifth Edition

Learning Objectives Serve as Memory Flag

Each chapter begins with a clearly defined set of Learning Objectives (LOs) that provide a quick reference to the chapter’s key aspects. These help students better anticipate what they will be studying and help instructors measure student’s understanding.

Pedagogy as Per Blooms’ Taxonomy

The pedagogy is arranged as per the Levels of Difficulty (LOD) which is derived from Blooms’ Taxonomy.

S indicates Knowledge and Comprehension based easy-to-solve problems

M indicates Application and Analysis based medium-difficulty problems

D indicates Synthesis and Evaluation based high-difficulty problems.

Point Sources and Their Arrays

Chapter 5

Learning Objectives

After reading this chapter, you will be able to:

LO 1 Understand the point source radiatorsLO 2 Know arrays of two point sourcesLO 3 Explain the linear arrays of n point sourcesLO 4 Discuss the arrays with different types of amplitude distributionsLO 5 Describe the continuous arrays and Huygens’ principle

IntroductIon

In Chap. 2 an antenna was treated as an aperture. In this chapter, an antenna is first considered as a point source and later the concept is extended to the formation of arrays of point source. This approach is of great value since the pattern of any antenna can be regarded as produced by an array of point sources. Further the initial discussion relating to arrays is confined to isotropic point sources, which may represent different kinds of antennas. Later the discussion is extended to encompass more general case of nonuniform distribution.

With the information of this chapter and the computer programs on the book’s website, an array produc-ing almost any desired patterns may be designed.

5.1 PoInt Source

At a sufficient distance in the far field of an antenna, the radiated fields of the antenna are transverse and the power flow or the Poynting vector (W/m2) is radial as at the point O at a distance R on the observation circle in Fig. 5.1. It is convenient in many analyses to assume that the fields of the antenna are everywhere of this type. In fact, we may assume, by extrapolating inward along the radii of

LO1Understand the point source radiators

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Within the Chapter Exercises

More than 380 unsolved problems, prompt the stu-dents to apply the material as they read. This offers great retention through looping mechanism. More than 150 solved examples are given to develop a clear understanding of the concepts.

Emphasis on Crucial Concepts

Keywords and Concepts have been highlighted throughout the book to aid ease of understanding.

Antenna Basics 17

Solution (a) E(q) at half-power = 0.707. Thus, 0.707 = cos q cos 2q = 1/ 2 .

1

1

1 1cos 2 = 2 = andcos2 cos 2 cos

1 1= cos2 2 cos

q qq q

qq

-

-

Ê ˆÁ ˜Ë ¯

Ê ˆÁ ˜¢Ë ¯

Iterating with q¢ = 0 as a first guess, q = 22.5°. Setting q¢ = 22.5°, q = 20.03°, etc., until after next iteration q = q¢ = 20.47° @ 20.5° and

HPBW = 2q = 41° Ans. (a) (b) 0 = cos q cos 2q, so q = 45° and FNBW = 2q = 90° Ans. (b)

Important

Although the radiation pattern characteristics of an antenna involve three-dimensional vector fields for a full representation, several simple single-valued scalar quantities can provide the information required for many engineering applications. These are:

d Half-power beamwidth, HPBW d Beam area, WA d Beam efficiency, eM d Directivity D or gain G d Effective aperture Ae

The half-power beamwidth was discussed above. The others follow.

2.1.2.3 Beam Area (or Beam Solid Angle) WA

In polar two-dimensional coordinates an incremental area dA on the surface of a sphere is the product of the length r dq in the q-direction (latitude) and r sin q df in the f-direction (longitude), as shown in Fig. 2.5.

Thus, dA = (r dq)(r sin q df) = r2 dW (2.5)

where dW = solid angle expressed in steradins (sr) or square degrees (°) dW = solid angle subtended by the area dA

The area of the strip of width rdq extending around the sphere at a constant angle q is given by (2pr sin q) (r dq). Integrating this for q values from 0 to p yields the area of the sphere. Thus,

Area of sphere = 2 2 200

2 sin = 2 [ cos ] = 4r d r rp pp q q p q p-Ú (2.6)

where 4p = solid angle subtended by a sphere, sr.

FNBW� 90�

HPBW� 41�

E(�)� cos � cos 2�

�

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28 Antennas and Wave Propagation

If the same dipole is used at a longer wavelength so that it is only 0.1l long, the current tapers almost linearly from the central feed point to zero at the ends in a triangular distribution, as in Fig. 2.9.1(b). The average current is 1/2 of the maximum so that the effective height is 0.5l.

Interpretation Thus, another way of defining effective height is to consider the transmitting case and equate the effective height to the physical height (or length l) multiplied by the (normalized) average current or

av00 0

1= ( ) = (m)hp

e pI

h I z dz hI IÚ (2.46)

where he = effective height, m hp = physical height, m Iav = average current, A

It is apparent that effective height is a useful parameter for transmitting tower-type antennas.9 It also has an application for small antennas. The parameter effective aperture has more general application to all types of antennas. The two have a simple relation, as will be shown.

For an antenna of radiation resistance Rr matched to its load, the power delivered to the load is equal to

2 2 21= = (W)

4 4r r

V h EP

R R (2.47)

In terms of the effective aperture the same power is given by

2

0= = (W)e

eE A

P SAZ

(2.48)

where Z0 = intrinsic impedance of space (= 377 W)Equating (2.47) and (2.48), we obtain

2

20

0= 2 (m) and = (m )

4r e e

e er

R A h Zh A

Z R (2.49)

Thus, effective height and effective aperture are related via radiation resistance and the intrinsic imped-ance of space.

summary We have discussed the space parameters of an antenna, namely, field and power patterns, beam area, directivity, gain and various apertures. We have also discussed the circuit quantity of radiation resistance and alluded to antenna temperature, which is discussed further in Sec. 18.1. Figure 2.10 illustrates this duality of an antenna.

9 Effective height can also be expressed more generally as a vector quantity. Thus (for linear polarization) we can write V = he ¥ E = heE cosq where he = effective height and polarization angle of antenna, m E = field intensity and polarization angle of incident wave, V/m q = angle between polarization angles of antenna and wave, degIn a still more general expression (for any polarization state), q is the angle between polarization states on the Poincaré sphere (see Sec. 2.3.3).

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30 Antennas and Wave Propagation

where l = wavelength Iav = average current I0 = terminal current

The power density, or the Poynting vector, of the incident wave at the dipole is related to the field intensity by

2

= ES

Z (2.53)

where Z = intrinsic impedance of the medium. In the present case, the medium is free space so that Z = 120p W. Now substituting Eqs. (2.51), (2.52)

and (2.53) into Eq. (2.50), we obtain for the maximum effective aperture of a short dipole (for Iav = I0)

2 2 2

2 2em 2 2 2

120 3= = = 0.1198320

E lA

E l

p l l lpp

Ans. (a)

(b) 2

e2 2

4 4 0.119= = = 1.5AD

p p ll l

¥ Ans. (b)

attention A typical short dipole might be l/10 long and l/100 in diameter for a physical cross-sectional aperture of 0.001l2 as compared to the 0.119l2 effective aperture of Example 2.1.7. Thus, a single dipole or linear antenna may have a physical aperture that is smaller than its effective aperture. However, a broadside array of many dipoles or linear antennas has an overall physical aperture that, like horns and dishes, is larger than its effective aperture. On the other hand, an end-fire array of dipoles, as in a Yagi-Uda antenna, has an end-on physical cross-section that is smaller than the antenna’s effective aperture. Thus, depending on the antenna, physical apertures may be larger than effective apertures, or vice versa.

Example 2-1.8 Effective aperture and directivity of linear l/2 dipoleA plane wave incident on the antenna is traveling in the negative x-direction as in Fig. 2.11a. The wave is linearly polarized with E in the y-direction. The equivalent circuit is shown in Fig. 2.12b. The antenna has been replaced by an equivalent or Thévenin generator. The infinitesimal voltage dV of this generator due to the voltage induced by the incident wave in an infinitesimal element of length dy of the antenna is

2= cos ydV E dy

pl

(2.54)

dy

z

I0

I

y

RTIncidentwave

y

x(a) (b)

dV RA

dI

RT

�

�/2

Figure 2.12 Linear l/2 antenna in field of electromagnetic wave (a) and equivalent circuit (b).

M

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Point Sources and Their Arrays 141

Unsolved Problems for lo 2

*5-2.1 Two point sources (a) Show that the relative E(f) pattern of an array of two identical isotropic in-phase point sources arranged as in Fig. P5-2.1 is given by E(f) = cos[(dr/2)sin f], where dr = 2pd/l. (b) Show that the maxima, nulls and half-power points of the pattern are given by the following relations:

Maxima: arc sin lf Ê ˆ= ±Á ˜Ë ¯k

d

Nulls: (2 1)arc sin2

lf +È ˘= ±Í ˙Î ˚k

d

Half-power points: (2 1)arc sin4

lf +È ˘= ±Í ˙Î ˚k

dwhere k = 0, 1, 2, 3,…(c) For d = l find the maxima, nulls and half-power points, and from these points and any additional points that may be needed plot the E(f) pattern for 0° £ f 360°. There are four maxima, four nulls and eight half-power points, (d) Repeat for d = 3l/2, (e) Repeat for d = 4l, (f) Repeat for d = l/4. Note that this pattern has two maxima and two half-power points but no nulls. The half-power points are minima.

[Ans. (c) Max. at 0°, 180°, ±41.8°, ±38.2° Nulls at ±19.4°, ±90°, ±160.6°Half-power at ±9.6°, ±170.4°, ±30°, ±150°, ±56.5°, ±123.5°. (d) Max. at 0°, ±90°, 180°]

5-2.2 Two point sources (a) What is the expression for E(f) for an array of two point sources arranged as in the figure for Prob. 5.2.1? The spacing d is 3l/8. The amplitude of source 1 in the f plane is given by |cos f| and the phase by f. The amplitude of the field of source 2 is given by |cos(f – 45°)| and the phase of the field by f – 45°.

(b) Plot the normalized amplitude and the phase of E(f) referring the phase to the centre point of the array.

*5-2.3 Two-source broadside array (a) Calculate the directivity of a broadside array of two identical isotropic in-phase point sources spaced l/2 apart along the polar axis, the relative field pattern being given by

cos cos2

Ep qÊ ˆ= Á ˜Ë ¯ where q is the polar angle.

(b) Show that the directivity for a broadside array of two identical isotropic in-phase point sources spaced a distance d is given by

21 ( /2 )sin(2 / )

Dd dl p p l

=+

[Ans. (a) 2]

5-2.4 Two-source end-fire array (a) Calculate the directivity of an end-fire array of two identical isotropic point sources in phase opposition, spaced l/2 apart along the polar axis, the relative field pattern being given by

sin cos2

Ep qÊ ˆ= Á ˜Ë ¯ where q is the polar angle.

�

1

d

2

Fig. P5-2.1 Two-point sources

M

S

S

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Antenna Basics 29

SPACE QUANTITIES

PHYSICALQUANTITIES

CIRCUITQUANTITIES

• Field patterns• Size

• Weight

Currentdistribution

ANTENNA(transition

region)

• Polarization, LP, CP, EP

• Power patterns, Pn(�, �)

• Beam area, �A

• Directivity, D

• Gain, G

• Effective aperture, Ae

• Antenna impedance, ZA

• Antenna temperature, TA

• Radiation resistance, Rr

• Radar cross-section, �

E�(�, �)E�(�, �)

�(�, �)

All about antennas at a glance

Figure 2.10 The parameters or terminology of antennas illustrating their duality as a circuit device (with resistance and temperature) on one hand and a space device (with patterns, polarization, beam area, directivity, gain, aperture and radar cross-section) on the other. Other antenna quantities are its physical size and bandwidth (involving impedance, Q and pattern).

Example 2-1.7 Effective aperture and direc-tivity of a short dipole antennaA plane wave is incident on a short dipole as in Fig. 2.11. The wave is assumed to be linearly polarized with E in the y-direction. The current on the dipole is assumed con-stant and in the same phase over its entire length and the terminating resistance RT is assumed equal to the dipole radiation resistance Rr. The antenna loss resistance RL is assumed equal to zero. What is (a) the dipole’s maximum effective aperture and (b) its directivity?Solution (a) The maximum effective aperture of an antenna is

2

em =4 r

VA

SR (2.50)

where the effective value of the induced voltage V is here given by the product of the effective electric field intensity at the dipole and its length, that is,

V = El (2.51) The radiation resistance Rr of a short dipole of length l with uniform current will be shown later to be

22 22 2

av av2

0 0

80= = 790 ( )rI Il l

RI I

pll

Ê ˆÊ ˆ Ê ˆ WÁ ˜Á ˜Á ˜ Ë ¯Ë ¯ Ë ¯ (2.52)

M

Direction ofincidentwave

Shortdipole

z

yRr

l

I

x

Figure 2.11 Short dipole with uniform current induced by incident wave.

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8 Antennas and Wave Propagation

ObjecTive Type QueSTiOnS

1.1 The first antenna was built in (a) 1846 (b) 1866 (c) 1886 (d) 1906 1.2 The following is referred to as primary dimension (a) Area (b) Volume (c) Velocity (d) Length 1.3 The dimension of a virus corresponds to the wavelengths of (a) GHz wave (b) THz wave (c) PHz wave (d) EHz wave 1.4 The frequency (in Hz) of visible light is around (a) 1012 (b) 1015 (c) 1018 (d) 1020

1.5 The VHF band covers frequencies between (a) 30–300 MHz (b) 300–3000 kHz (c) 30–300 kHz (d) 3–30 GHz

referenceS

S

S

S

S

S

d The dimensions of length, mass, time, electric current, temperature and luminous intensity are considered as the fundamental dimensions.

d The derived dimensions, in terms of these, are referred to as secondary dimensions. d A unit is a standard or a reference by which a dimension can be expressed numerically. d The units for the fundamental dimensions are called fundamental or base units whereas those for

other dimensions are called secondary or derived units.LO 3: Identify the symbols, notations and numbering used in the text

d Different symbols and notations are used for scalar and vector quantities and for their units for easy differentiation.

d Article, table, figure and equation numbers are systematized for easy identification and reference.LO 4: Carry out the dimensional analysis

d The dimensional analysis is useful for determining the dimensions of a quantity. d For correctness, it is a necessary that every equation be dimensionally balanced; it is, however, not a

sufficient condition for correctness.LO 5: Discuss electromagnetic spectrum and the radio frequency bands

d Theoretically, electromagnetic spectrum encompasses all frequencies ranging from 0+ to infinity. d The segments and sub-segments of electromagnetic spectrum are referred to as frequency bands and

sub-bands.

Bose, J. C. Collected Physical Papers. Longmans, Green, 1927.Bose, J. C. “On a Complete Apparatus for the Study of the Properties of Electric Waves.” The London, Edinburgh and

Dublin Philosophical Magazine and Journal of Science 43 (October 1896).Brown, G. H. “Marconi.” Cosmic Search 2 (1980): 5–8.

Levels of DifficultyS Simple: Level 1 and Level 2 CategoryM Medium: Level 3 and Level 4 CategoryD Difficult: Level 5 and Level 6 Category

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Preface to the Adapted Fifth Edition xxiii

Chapter-End Exercises

Pedagogy includes Objective Type Questions, including questions from GATE examination, and References for additional reading.

80 Antennas and Wave Propagation

LO 9: Discuss the antenna applications d Various services operate in different frequency ranges d Antennas can be classified either in accordance with the frequency or applications

Objective type QueStiOnS

3.1 A point source is an antenna (a) Located at a point (b) Has point-like configuration (c) Observed from a far distance (d) Observed from a close distance 3.2 The radiation resistance of a dipole is (a) 73 W (b) 36.5 W (c) 50 W (d) 100 W 3.3 A wire antennas may be fed (a) In its centre (b) At its left end (c) At its right end (d) Anywhere 3.4 Loop antennas in conjunction with sense (wire) antennas are very frequently used as (a) Radio antennas (b) TV antennas (c) Mobile antennas (d) Direction finders 3.5 The vertical slots may result in (a) Vertical polarization (b) Horizontal polarization (c) Circular polarization (d) Elliptical polarization 3.6 Helical antennas are (a) Circularly polarized with high gain (b) Circularly polarized with low gain (c) Elliptically polarized with high gain (d) Elliptically polarized with low gain 3.7 Both loop and dipole have (a) Nonidentical field patterns but with E and H interchanged (b) Identical field patterns but with E and H interchanged (c) Perfectly nonidentical field patterns in all respect (d) Perfectly identical field patterns in all respect 3.8 Wideband antennas constancy of the following parameter(s) is maintained over a wide range of

frequency (a) Radiation resistance (b) Signal-to-noise ratio (c) Antenna temperature (d) Antenna impedance and radiation

characteristics.

reFerenceS

S

S

S

S

S

S

S

S

Baker, D. E., and C. A. Van der Neut. “A Compact, Broad-band, Balanced Transmission Line Antenna from Double-Ridged Waveguide.” Symposium on IEEE Antennas and Propagation Society, pp. 568–570, Albuquerque, 1982.Hoveinsen, S. A. Radar System Design and Analysis. USA: Artech House, 1984.Jesic, H. Antenna Engineering Handbook. USA: McGraw-Hill, 1981.

Kerr, J. L. “Short Axial Length Broad Band Horns.” IEEE Transaction on Antennas and Propagation AP-21 (Septem-ber 1973): 710–714.Shin, J. and D. H. Schaubert. “A Parametric Study of Stripline-Fed Vivaldi Notch-Antenna Arrays.” IEEE Anten-nas and Propagation 47 (May 1999): 879–886.

AWP-03.indd 80 7/19/2017 9:33:14 AM

Broadband and Frequency-independent Antennas 485

reFerenceS

Atia, A. E., and K. K. Mei. “Analysis of Multiple Arm Conical Log-Spiral Antennas.” IEEE Transaction on Antennas and Propagation AP-19 (May 1971): 320–331.Bawer, R., and J. J. Wolfe. “A Printed Circuit Balun for Use with Spiral Antennas.” IRE Transactions on Microwave Theory and Techniques MTT-8 (May 1960): 319–325.Brown, G. H., and O. M. Woodward. “Experimentally Determined Radiation Characteristics of Conical and Triangular Antennas.” RCA Review 13 (December 1952): 425–452.Butson, P. O., and G. T. Thomson. “A Note on the Calcula-tion of the Gain of Log-Periodic Dipole Antennas.” IEEE Transaction on Antennas and Propagation AP-24 (January 1976): 105–106.Carrel, R. L. “The Design of Log-Periodic Dipole Antennas.” IRE International Convention Record 1 (1961): 61–75.Chatterjee, J. S. “Radiation Field of a Conical Helix.” Journal of. Applied Physics 24 (May 1953): 550–559.Chatterjee, J. S. “Radiation Characteristics of a Conical Helix of Low Pitch Angle.” Journal of Applied Physics 26 (March 1955): 331–335.Cheong, W. M., and R. W. P. King. “Log Periodic Dipole Antenna.” Radio Science 2 (November 1967): 1315–1325.Deschamps, G. A. “Impedance Properties of Complemen-tary Multiterminal Planar Structures.” IRE Transaction on Antennas and Propagation AP-7 (December 1959): S371–378.DuHamel, R. H., and D. E. Isbell. “Broadband Logarithmi-cally Periodic Antenna Structures.” IRE National Conven-tion Record pt. 1 (1957): 119–128.Dyson, J. D. “The Equiangular Spiral Antenna.” IRE Transaction on Antennas and Propagation AP-7 (April 1959): 181–187.Dyson, J. D. “The Unidirectional Spiral Antenna.” IRE Transaction on Antennas and Propagation AP-7 (October 1959): 329–334.Dyson, J. D., and P. E. Mayes. “New Circularly-Polarized Frequency-Independent Antennas with Conical Beam or Omnidirectional Patterns.” IRE Transaction on Antennas and Propagation AP-9 (July 1961): 334–342.

Herbert, J. R. Very High Frequency Techniques RRL, Radio Research Laboratory Staff Chap. 4. United States: McGraw-Hill, 1947.Isbell, D. E. “Log Periodic Dipole Arrays.” IRE Trans-action on Antennas and Propagation AP-8 (May 1960): 260–267.Jordan, E. C., G. A. Deschamps, J. D. Dyson, and P. E. Mayes. “Developments in Broadband Antennas.” IEEE Spectrum, 1 (April 1964): 58–71.Kraus, J. D. “Helical Beam Antenna.” Electronics 20 (April 1947): 109–111.Mayes, P. E. “Frequency-Independent Antennas: Birth and Growth of an Idea.” IEEE Antennas and Propagation Society Newsletter 24 (August 1982): 5–8.Mayes, P. E., and J. D. Dyson. “A Note on the Difference between Equiangular and Archimedes Spiral Antennas.” IRE Transactions on Microwave Theory and Techniques MTT-9 (March 1961): 203–205.Mayes, P. E., and R. L. Carrel. “Log Periodic Resonant-V Arrays.” San Francisco Wescon Conference (August 1961).Mushiake, Y. J. IEE Japan, 69 (1949).Nakano, H., T. Mikawa, and J. Yamauchi. “Numerical Analysis of Monofilar Conical Helix.” IEEE AP-S Inter-national Symposium, 1 (1984): 177–180.Rumsey, V. H. (1) Frequency Independent Antennas. United States: Academic Press, 1966.Schellkunoff, S. A. Electromagnetic Waves Chap. 11. New York: Van Nostrand, 1943.Springer, P. S. “End-Loaded and Expanding Helices as Broad-Band Circularly Polarized Radiators.” Electronic Subdivision Technical. Report 6104, Wright-Patterson AFB, 1950.Uda, S., and Y. Mushiake. “Input Impedance of Slit Antennas.” Technology Reports of the Tohoku University 14, (1949) pp. 46–59.Vito, G. De., and G. B. Stracca.“Comments on the Design of Log-Periodic Dipole Antennas.” IEEE Transaction on Antennas and Propagation AP-21 (May 1973): 303–308; (AP-22 (September 1974) 714–718).

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Summary

A detailed chapter-end summary related to LOs covered in the chapter is provided for a quick review of the important concepts.

54 Antennas and Wave Propagation

➜Review

SummaryLO 1: Understand essential and important parameters of antenna from both circuit and field points of view

d Radio antenna is the structure associated with the region of transition between a guided wave and a free-space wave, or vice versa.

d Radiation resistance is a fictitious resistance which when substituted in series with an antenna will consume the same power as is actually radiated by the antenna.

d Solid angle (beam area) is the angle subtended by an area expressed in steradians of square degrees. d Radiation intensity is the power radiated by an antenna per unit solid angle. d Radiation pattern is the graphical representation of the field pattern of radiation from an antenna as

a function of direction/space coordinates. d E-field (radiation) pattern defined in terms of electric field strength E is called E pattern. d H-field (radiation) pattern defined in terms of magnetic strength H is called H pattern. d E and H patterns are also termed as radiation density patterns or spatial variation of E or H. d Power (radiation) pattern is the trace of received power P per unit solid angle (watts per steradians). d Beam width is the measure of directivity of an antenna or the angular measure of HPBW. d Half-power beam width (HPBW) of an antenna is the angular measurement between the directions

in which the antenna is radiating half of the maximum power. d Beam width between first two nulls (BWFN) is the angular measurement between the directions

radiating no power. d Antenna (total) efficiency is the ratio of the total power radiated by the antenna to the total power fed

to the antenna. It is the sum of radiation efficiency, conditional efficiency and dielectric efficiency. d Beam efficiency is the ratio of the main beam area to the total beam area. d Gain is the measure of squeezed/concentrated radiations in a particular direction with respect to an

omni (point source). d Power gain is the ratio of radiation intensity in a given direction to the average total power. d Directive gain is the ratio of power density in a particular direction at a given point to the power that

would be radiated at the same distance by an omni antenna. d Directivity is the maximum directive gain. d Effective height/length is the ratio of induced voltage at the terminal of the receiving antenna under

an open circuit condition to the incident electric field intensity or strength. d Effective (collecting) aperture is the ratio of power radiated in watts to the Poynting vector of the

incident wave. The effective aperture accounts for the captured/collected power. d Scattering aperture is the aperture which accounts for the scattered power in an antenna. d Loss aperture is the aperture which accounts for the power loss in an antenna. d Antenna (equivalent noise) temperature is the fictitious temperature at the input of an antenna, which

would account for noise DN at the output. DN is the additional noise introduced by the antenna itself. d Signal-to-noise ratio is the criterion of detectability of a signal or the measure of quality of network

vis-à-vis its deficiency and imperfections. d Front-to-back ratio is the ratio of power radiated in the desired direction to the power radiated in

the opposite direction. d Driving point or terminal impedance is the impedance measured at the input terminals of an antenna. d Self-impedance is the impedance of an isolated antenna, i.e. when there is no other antenna in its

vicinity.

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Chapter organiSation

The text of the present book is divided in to 23 chapters the contents of which are as under.

Chapter 1 includes a brief history of evolution of antennas, symbols, notations, units and dimensions of parameters, numbering of figures, examples, problems and equations, dimensional analysis, the Electromag-netic Spectrum and the Radio Frequency Bands.

Chapter 2 includes various antenna parameters, fields due to oscillating dipole, classification of polariza-tion and the antenna theorems.

Chapter 3 introduces various members of the antenna family and the antenna arrays. It also includes the applications of antennas in different frequency ranges.

Chapter 4 is devoted to understand radiation phenomenon with the aid of field relations mainly in terms of Maxwell’s equations and retarded (time varying) potential. It includes the field due to an alternating current element (oscillating dipole), electrostatic field, induction field, Hertzian dipole, the power radiated by this current element and the far and near fields due to sinusoidal current distribution.

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xxiv Preface to the Adapted Fifth Edition

Chapter 5 is solely devoted the point sources, their power, field and phase patterns and the radiation inten-sity. It includes a Power theorem and its application. It also discusses the array of two and n isotropic, non-isotropic, similar and dissimilar point sources. It also includes pattern multiplication and pattern synthesis. It describes arrays with various types of distributions, the Huygens’ principle and its application.

Chapter 6 mainly deals with various aspects of dipoles and their arrays. It describes the broadside and end-fire arrays formed from dipoles, their field patterns, gain and impedances and the effect of ground on their perfor-mance. Besides, it also discusses various types of antennas formed from wires. These include long-wire, Yagi-Uda, V, rhombic, beverage antennas and curtain arrays. It also includes Folded Dipole and the feed methods.

Chapter 7 discusses different aspects of loop, slot and horn antennas including their types, radiation patterns impedances and feeds. In connection with the slot antennas it describes the Babinet’s principle.

Chapter 8 discusses various aspects of helical beam antennas including their geometry and modes. It thorough-ly describes the monofilar axial-mode helical antennas, their design considerations, wideband characteristics and different applications. It also includes multifilar helical antennas and its comparison with the monofilar.

Chapter 9 describes various types of reflectors. These include flat sheet reflector, corner reflector, passive (Retro) corner reflector, parabolic reflector, paraboloidal reflector, spherical reflector and Cassegrain antenna. It includes their salient features, patterns and feed methods.

Chapter 10 discusses different types of lens antennas including non-metallic dielectric lens antennas. It further describes artificial dielectric lens antennas; E and H plane metal-plate lens antennas, reflector-lens antenna, Polyrod, multiple-helix, Luneburg and Einstein lenses.

Chapter 11 includes broad-band or frequency-independent antennas. These include conical, biconical, disk-cones, bow-tie, spiral, log-spiral, conical-spiral and log-periodic antennas. It also describes composite Yagi-Uda-corner-log- periodic array.

Chapter 12 deals with the various aspects of cylindrical antennas. It also includes integral-equation method and the moment method.

Chapter 13 describes various types of frequency-selective surfaces and periodic structures. It also includes their transmission and reflection properties, complementary surfaces, Babinet’s principle and polarizers.

Chapter 14 deals with the microstrip antennas, their types, salient features, basic structures, field distribution, mathematical relations, feed methods and arrays. It also describes methods for tuning, increasing bandwidth and analysis. It also includes advantages, limitations and applications of microstrip antennas.

Chapter 15 includes antennas for mobile communications systems viz. mobile terminal antennas, base sta-tion antennas, MIMO antennas, active antennas, reconfigurable antennas and EBG based antennas.

Chapter 16 describes various specialized and application-oriented antennas. It also includes antennas for satellite communication, landing, remote sensing and other applications.

Chapter 17 discusses various types of aperture distributions, efficiencies, surface irregularities and gain–loss, off-axis operation of parabolic reflectors, shaped reflectors and spherical reflectors, Cassegrain and offset feeds.

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Preface to the Adapted Fifth Edition xxv

Chapter 18 deals with the antenna temperature, system temperature, signal-to-noise ratio, passive remote sensing and the radar cross-section.

Chapter 19 deals with evaluation of self and mutual impedances of antennas and combinations thereof in different configurations.

Chapter 20 deals with the Fourier transform relation between various types of aperture distributions and the far-field patterns. It includes spatial frequency response and pattern smoothing, aperture synthesis and multi-aperture arrays and grating lobes.

Chapter 21 is solely devoted to various types of baluns, their salient features and applications.

Chapter 22 deals with the antenna measurements, the basic concepts and typical sources of errors involved therein. It includes measurement of ranges and different antenna parameters. It also describes the working of different instruments, analysers and anechoic chambers and absorbing materials.

Chapter 23 describes basics of wave propagation including the definition and classification. It also discusses wave environment, different modes of wave propagation and wave applications. This chapter thoroughly describes various aspects of the ground waves, space waves and the sky waves.

For the convenience of students this text also includes a number of appendices. Appendix A1 includes the Antenna system relations; A2, Transmission line formulae; A3, Reflection and transmission coefficients and VSWR; A4 Characteristic impedance of coaxial, two-wire and Microstrip transmission lines; A5, Characteristic impedance of transmission lines in terms of distributed parameters; A6, Material constants; A7 Permittivity relations; A8, Maxwell’s equations; A9, Bessel functions; A10 Value of x and A11, Value of n. Besides Appendix B1 includes the list of Books; B2, Video tapes; B3, Selected articles for further reading; C, Computer programs; D1, Absorbing materials; D2, Ferrite Materials; E, Measurement error and F, Answers to objective questions. In end, the book is aided with the subject and author indexes.

online learning Center SupplementS

The web supplements can be accessed at: http://www.mhhe.com/kraus/a5asie, which contain following material

For Instructors: d Solutions Manual, d PowerPoint Lecture Slides

For Students: d Chapters on Large and Unique Antennas, Terahertz Antenna and Antenna Array Analysis and Synthesis d Web links for useful reference material

aCknoWledgementS

I am thankful to all teachers, students and readers for valuable advice and suggestions, who used the ear-lier editions of this book. All these individuals have influenced this edition and I hope this support would continue in future as well.

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xxvi Preface to the Adapted Fifth Edition

I am thankful to the almighty God who gave me strength for the completion of this task. I express my gratitude to my (late) parents, my relatives, friends, colleagues and to all members of my family. I am indeed indebted to all my teachers, from primary to the university level, for enhancing my knowledge.

The following reviewers are greatly appreciated for providing their valuable suggestions and comments:

Jugal Kishore I.T.S. Engineering College, Greater Noida, Uttar PradeshNirmal Singh Haryana Engineering College, HaryanaAbhijeet Singh Shri Ramswaroop Memorial Group of Professional Colleges, Lucknow, Uttar

PradeshGyanendra Pratap Singh Vidya College of Engineering, Meerut, Uttar PradeshAnkit Ponkia Shantilal Shah Engineering College, Bhavnagar, GujaratS. Ramesh Valliammai Engineering College, Kattankulathur, Tamil Nadu N. Jayapal Kongunadu College of Engineering and Technology, Tholurpatti, Tamil NaduD. Selvaraj Panimalar Engineering College, Chennai, Tamil NaduHenridass Arun Sri Sai Ram Engineering College, Chennai, Tamil NaduLakshmi C Sriram Engineering College, Perumalpattu, Tamil NaduPremkumar. M SSM Institute of Engineering and Technology, Dindigul, Tamil NaduK. Vijaya B.M.S. College of Engineering, Bangalore, KarnatakaV. R. Anitha Sree Vidyanikethan Engineering College, Tirupati, Andhra Pradesh

Ahmad Shahid Khan

Publisher’s Note:

McGraw Hill Education (India) invites suggestions and comments, all of which can be sent to info.india@mheducation.com (kindly mention the title and author name in the subject line) or can be directly sent to the authors at ahmadshahidkhan@rediffmail.com.

Piracy-related issues may also be reported.

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