دانلود کتاب Electromagnetic Waves, Materials, and Computation with MATLAB

The subject of electromagnetics is still a core subject of the undergraduate electricalengineering(EE) curriculum; however, at most of the universities in United States, the timeallotted to teach it is cut into half (one 3-credit course instead of two). The present graduateswith BS degree in EE being rushed through the same curriculum content in a shorter timeoften miss the concepts and depend on a lot of formulas which they use as a recipe for somecalculations based on an example worked out in the book. Some of them are fortunate totake a follow-up special elective course in microwaves or RF design or antennas or fiberoptics, and so on, thus partly reinforcing one application area. Readily available commercialsoftware allows them to do routine calculations and design without having a conceptualunderstanding of the expected solution. The commercial software is so user-friendly thatwe usually get a beautiful colored visualization of the solution, even if it is a wrong simulationof the physical problem. After getting one or two mild reprimands from the boss in anew employment after graduation, the new graduate realizes the need to have a fairly goodidea of what is the appropriate model to be simulated and what qualitative result is to beexpected. Though the software is very useful, it is not a substitute for a conceptual understandingof the steps involved in solving the problem. Fortunately, for him, there is probablya university which offers graduate courses and there is an instructor or professor whounderstands that these bright students recruited by some of the top companies are not lesssmart than the employees recruited by the company, say a decade or two ago. On the otherhand, they are very knowledgeable and comfortable using the computers and onlineresources. They are willing to challenge themselves to learn quickly to think in terms ofconcepts and analysis rather than routine calculations; however, they would like to learnthese through examples that connect them to a technological application. Also, they find itinteresting if they find that the technique they learnt in one technological area by an indepthstudy of that particular area can be applied to another technological area having thesame basis of engineering science, in this case electromagnetics. Such graduate students,even if they enjoy the electromagnetics per se, cannot afford to take more than one or twograduate courses in electromagnetics before specializing in one of the technological areasfor which electromagnetics is a base.In a discipline as classical as electromagnetic theory, there are many excellent textbooks.Many of us who teach and do research in electromagnetics had the benefit of thesegraduate-level courses based on classical textbooks, which are precommercial electromagneticsoftware. Those who are motivated to continue this classical mode of learning anddoing research in electromagnetics will continue to be inspired by the thorough mathematicaltreatment of all aspects learning them from these classical graduate-level textbooksover a period of 2 or 3 years.I believe that in teaching electromagnetics to EE students as opposed to the physics students,we can make some subtle changes in the presentation of the material. The firstchange is to exploit the strong circuit background of the EE students and treat transmissionlines as distributed circuits.Given below are some thoughts on the motivation, reasoning, and general themes indeveloping the material in this book presented in Parts I through V.1. Transmission lines as distributed circuits are a logical extension of the lumpedparameter circuit theory. For electrical engineers, scalar waves on the transmissionlines with voltage and current as the dependent variables somehow seem tobe less abstract and give the basic framework (clutch) in which electrical engineerscan think. Transmission line analogies even if they are not physical (artificial)seem to help electrical engineers to grasp more abstract concepts.2. I have taken the liberty of defining a simple electromagnetic medium as one whereε, μ, and σ are all scalar constants. This is to correspond to the gross parameterdescription of the circuits as capacitance C, inductance L, and conductance G, orresistance R. It also roughly corresponds to the problems we usually solve in theundergraduate course. Some purists may object to this definition. They may liketo think of a free-space medium as the only simple medium. They are willing toextend the definition of a simple medium to an ideal isotropic dielectric. Anythingbeyond isotropic dielectric is a complex media.3. I have taken a utilitarian view in distinguishing the simple medium problemfrom the complex medium problem. The four Maxwell’s equations are the samefor both, and the electromagnetic properties of the materials are introducedthrough constitutive relations. Specification of the boundaries and the sourcescompletes the specification of the problem. Many practical problems can involvecomplex media as well as complicated boundaries. However, from the pedagogicalview point, one can classify the problems as (a) involving a simple mediumwith complicated boundaries or (b) a complex medium bounded by simple boundaries.For example, a simple boundary may be a planar surface, allowing Cartesiancoordinate descriptions.4. Part I of this book deals with electromagnetics of bounded simple media. Afterintroducing the equations in the time domain, the time-harmonic equations, wavepropagation solutions, and their applications are obtained for one-dimensional,two-dimensional, and then three-dimensional problems. In one-dimensionalproblems, planar boundaries and then the cylindrical boundary problems andapplications are considered. Starting from the first principles, the process ofobtaining the one-dimensional model (for the z-component of the vector potential,Az ) for the ideal problem of an infinitely long conducting filament along the z-axisexcited by a harmonic current is explained. Then considering the symmetriesinvolved in the problem, it is shown that Az is at the most a function of the cylindricalradial coordinate ρ. This is a simple example of building a model appropriateto the objectives of the investigation rather than getting bogged down withunnecessary details, which could increase the complexity of the problem. As anexample of increasing the complexity, one could solve the same problem by consideringa differential length of the filament as a Hertzian dipole and do the integrationwith infinite limits for the infinitely long filament.5. The ordinary differential equation of the above-mentioned problem is shown tohave a singularity at the origin and is shown to have two independent solutions,one of them having a singularity at the origin. After mentioning that the solutionto such equations can be obtained by power series, the series solution is given anddesignated as the Bessel function of the first kind of zero order. Bessel functionsare thus introduced, compared with trigonometric functions, and their applicationsare illustrated.6. The rectangular and cylindrical waveguides are used as examples of two-dimensionalproblems. After defining the waveguide problem, the well-knownseparation of variable–product solution technique of solving partial differential(PD) equations is illustrated. It is shown that the technique converts the PD equationsto the ordinary differential equations with constraints on the separation constants.In the discussions of special functions, the emphasis is on developing aninterest for these functions, facilitating their use in obtaining the eigenvalues, andeigenvectors of the ordinary differential equations. Use of fractional Bessel functionsis illustrated through sector waveguides. In these examples, the technique ofchoosing the appropriate functions from a template of admissible functions for theproblem based on given and implied (based on the physics of the problem) boundaryconditions are illustrated.7. Chapter 4 deals with a rectangular cavity as an example of a three-dimensionalproblem. The well-known approximation technique of obtaining the fields (eigenvectors)and resonant frequencies (eigenvalues), assuming the boundaries are perfectconductors, and then calculating the losses based on the surface current-flowon the walls of the cavity is illustrated. Homework problems are given to test whetherthe students are able to write by inspection, the solution for a cylindrical cavity.8. The waveguide and cavity problems of Chapters 4 and 5 are essentially based on thesolution of a scalar Helmholtz equation for the potential (Ez for the TM problemsand Hz for the TE problems). It became possible to do such decomposition becausefor these problems we could identify a longitudinal direction and a transverse plane.In the spherical geometry, we do not have such easily identifiable scalar potentials.In principle, the more general vector Helmholtz equation for the fields has to besolved. The mathematics thus becomes more involved. We can relate to the previoustechniques by first considering the solution F of the scalar Helmholtz equation inspherical coordinators and then relating it to the TMr and TEr modes through thedefined vectors M and N. In a one-semester course, one can omit this chapter sinceit can distract a student from a simpler conceptual understanding aimed so far.9. Chapter 6 approximates the scalar Helmholtz equation to the Laplace equationfor low-frequency (quasistatic) or static applications. A quick review of the onedimensionalproblems, the technique of using the template of the admissible functionsin the three main coordinate systems, and the expansion of an arbitraryfunction in terms of the orthonormal functions which were the modes (eigenvectors)of the solutions in Chapters 3 and 4 are illustrated. A large number of homeworkproblems are given to illustrate the application to the electromagneticproblems. Miscellaneous topics on waves, particularly Section 7.2, is written at acomparatively intuitive and comfortable level suitable for an undergraduate EEstudent. Section 7.3 is particularly interesting for those who would like to extendtheir strength in circuits and networks to high-frequency engineering. Sections 7.5through 7.7 are usually studied in greater depth as separate courses and areincluded here as an introduction to these topics. This concludes Part I of this book,dealing with the electromagnetics of simple bounded media.10. Part II of this book deals with electromagnetics of complex media. At least one ofthe electromagnetic parameters is not a scalar constant. Chapter 8 develops theconstitutive relations for various complex materials, including superconductors,mostly using classical simple models for the microscopic interactions.11. Effects of temporal dispersion, spatial dispersion, nonhomogeneity, and anisotropyon wave propagation are investigated taking cold plasma, warm plasma, magnetoplasma,anisotropic crystals as examples. A special case of time-varying mediumproblems, that is, a moving medium, is discussed in Chapter 14. Several techniquesof electromagnetic analysis are considered in some depth. Electromagnetic modelingand experimental simulations of plasmas, chiral materials, and left-handedmaterials are discussed in Chapter 9, under the heading of Artificial ElectromagnetMaterials.12. In Part II, the dominant effect of each kind of complexity is brought out. The goalof this part is to bring the system approach of relating the kind-of-complexityresultantdominant effect as an input–output description of a system element. Acombination of the system elements through interconnection of the system elementsin an approach of synthesis can bring a desired output. Section 10.10 mentionsone example: the combination of two undesirable dominant effects of (a)dispersion in broadening the pulse and (b) the nonlinearity in steepening thepulse into a desirable overall effect of preserving the pulse shape in the propagationof a soliton in the dispersive nonlinear medium.13. The purpose of Part III, Electromagnetic Computation, is to bring out the basis ofthe engines of various commercial electromagnetic software, widely used in theindustry. Algorithms of finite differences, moment method, finite-element method,and finite-difference time-domain method are developed and illustrated. Handcomputedsimple examples and MATLAB®-coded simple examples with only afew elements are used to explain the concepts behind the algorithms. The codingis also kept very simple translating the equations of the algorithm as directly aspossible. A few case studies of practical examples from transmission lines, waveguides,and electrostatic problems are given so that the student is able to developthe code and solve the problems. The students are encouraged to run the sameproblems on the commercial software to verify their result and get a feel for thealgorithm. Of course, some of the Commercial software have a lot more postprocessingcapabilities and more efficient and accurate engines, and the purpose ofthis part was not to discourage the student from using these commercial softwaresbut to use them with greater confidence and satisfaction.The three parts have enough material to serve as a textbook for two senior-level/firstyear-graduate-level courses, each of three semester credits. At the University ofMassachusetts Lowell, the material in various versions was used for such a purpose duringthe past 24 years (for the courses 16.507: Electromagnetic Waves and Materials, 16.532:Computational Electromagnetics). In each of these classes, about two-thirds of the studentswere from industries based on electromagnetic technologies.Part IV consists of appendices for various chapters. Some of them contain the details ofa derivation or explanation that is not central to the concept and likely to distract the readerfrom the main point being made and hence relegated to the appendix for completeness. Onthe other hand, some of the appendices contain advanced topics or newer topics of interestto a subset of the students. It gives the instructor a choice of advanced topics he caninclude as examples of topics of current research interest to the electromagnetic community.A third category of appendices are a basic exposure to an electromagnetic topic.Advanced discussion of the topic is not pursued but it is pointed out that it can proceed onlines very similar to the one in the chapter. For example, Chapter 13 deals with “OpticalWaves in Anisotropic Crystals.” The analysis is based on a constitutive relation relating Dwith E through permittivity tensor. Appendix 13A formulates the permeability tensor forthe complex medium of a ferrite in the presence of a background static magnetic field.Part V is an important pedagogic tool containing homework problems, 15-minute quizzes,and take-home examinations. The author used them in the following fashion. Afterthe lecture, some problems are assigned as homework, in the next class, the homework isbriefly discussed mostly to tell the importance of the problem in terms of a technologicalapplication, modeling tip, and the solution outline is provided. A quiz of 15-minute durationis administered periodically (every third or fourth 50-minute lecture class to checkwhether the central concepts in the homework are learnt). Midway through the semesterand at the end of the course, take-home or open-book examination is given where moresubstantial problems are set. The feedback from the students was always positive with thecomment that the questions in Part V was the most effective way they learnt the deeperimplication of the material in the other parts of the book.The solutions to the questions in Part V will be provided to the instructor through thedownloadable online component of this book. This book is so structured that a courseoutline can be picked from the table of contents to serve the needs of courses of three tosix semester credits with different starting points on different aspects of electromagnetics.Examples of such courses-outline will be included in the online component of this bookfor the benefit of the instructor. These are (UML stands for University of MassachusettsLowell):Course Outline A: one-semester 3-credit senior-elective-first-year graduate coursewith a prerequisite of one-semester 3-credit core undergraduate course inelectromagnetics;Course Outline B: (UML 16.507 Electromagnetic Waves and Materials) one-semester3-credit senior-elective-first-year graduate course with a prerequisite of twosemester3-credit each core undergraduate course in electromagnetics (UML16.360, UML 16.461);Course Outline C: (UML 16.532 Computational Electromagnetics) one-semester3-credit senior-elective-first-year graduate course with a prerequisite of twosemester3-credit each core undergraduate course in electromagnetics (UML16.360, UML 16.461);Course Outline D: (UML 16.607 Electromagnetics of Complex Media) one-semester3-credit second-year advanced graduate course in electromagnetics with a prerequisiteof first-year graduate course in Electromagnetics 16.507. This courseincludes an additional project/extra material.Though the book contains more material than can be reasonably covered in a one-semester3-credit course, I contend that this book is useful even for students who take onlyone graduate course in electromagnetics, since any of the course outlined above sets thetone and the rest of the material can be understood in a self-study as and when needed bythe student. I believe a graduate-level book should also serve as a starting point for someof the current and active research areas as well as spark an interest in such areas.This book is a companion to my research monograph (K10882) Electromagnetics ofTime-Varying Complex Media: Frequency and Polarization Transformer, Second Edition, which waspublished by CRC Press (Taylor & Francis Group) in April 2010. The connection betweenthe publications is established through the common theme of a few chapters in the twobooks. Chapters 10, 12, 19, and Appendix 10E of this book are the modified versions ofChapters 2, 6, 11, and Overview of the book K10882, respectively.This book aims to strike a balance between theory, intuitive approximate solutions, andthe use of commercial software and interpretation of the software solutions, of electromagneticproblems.