While there are so many books on general electromagnetic theory for graduate-level students, there are significantly fewer that concentrate on the radiation aspects as does this well-known work. Interfacing physics and electrical engineering, Dr. Papas's clearly written text discusses highly important topics in the theory of electromagnetic wave propagation and antennas in a way that reveals the inherent simplicity of the basic ideas and their logical development from the Maxwell field equation.
Chapter 1: Maxwell's field equations and those parts of electromagnetic field theory necessary for understanding the remainder of the book.
Chapter 2: How the dyadic Green's function can be used to compute radiation from monochromatic sources.
Chapter 3: Problems of radiation emitted by wire antennas and antenna arrays from the viewpoint of analysis and synthesis.
Chapter 4: Two methods of expanding a radiation field in multiples — one based on the Taylor expansion of the Helmholtz integrals and the other, on all expansion in spherical waves.
Chapter 5: Wave aspects of radio-astronomical antenna theory.
Chapter 6: Theory of electromagnetic wave propagation in a plasma medium describing the behavior of an antenna immersed in such a medium.
Chapter 7: Covariance of Maxwell's equations in material media and its application to phenomena such as the Doppler effect.
By unifying various topics under the single mantle of electromagnetic theory, Professor Papas has made the contents of this book easy to learn and convenient to teach. In addition, the book assembles much data previously available only in scattered research literature. The result is a superb graduate-level text that can also lend itself to self-instruction by researchers.
In this introductory chapter some basic relations and concepts of the classic electromagnetic field are briefly reviewed for the sake of easy reference and to make clear the significance of the symbols.
1.1 Maxwellâs Equations in Simple Media
In the mks, or Giorgi, system of units, which we shall use throughout this book, Maxwellâs field equations1 are
where E(r, t) =
electric field intensity vector, volts per meter
H(r, t) =
magnetic field intensity vector, amperes per meter
D(r,t) =
electric displacement vector, coulombs per meter2
B(r,t) =
magnetic induction vector, webers per meter2
J(r,t) =
current-density vector, amperes per meter2
Ï(r,t) =
volume density of charge, coulombs per meter3
r =
position vector, meters
t =
time, seconds
The equation of continuity
which expresses the conservation of charge is a corollary of Eq. (4) and the divergence of Eq. (2).
The quantities E(r,t) and B(r,t) are defined in a given frame of reference by the density of force f(r,t) in newtons per meter3 acting on the charge and current density in accord with the Lorentz force equation
In turn D(r,t) and H(r,t) are related respectively to E(r,t) and B(r,t) by constitutive parameters which characterize the electromagnetic nature of the material medium involved. For a homogeneous isotropic linear medium, viz., a âsimpleâ medium, the constitutive relations are
where the constitutive parameters
in farads per meter and Ό in henrys per meter are respectively the dielectric constant and the permeability of the medium.
In simple media, Maxwellâs equations reduce to
The curl of Eq. (9) taken simultaneously with Eq. (10) leads to
Alternatively, the curl of Eq. (10) with the aid of Eq. (9)...
