Applied Electromagnetics

ABOUT THE AUTHOR Stuart M. Wentworth received his B.S degree in Chemical Engineering from Auburn University, Alabama, in 1982 and his M.S. (1987) and Ph.D. (1990) degrees in Electrical Engineering from the University of Texas at Austin. He has been a member of the Electrical & Computer Engineering faculty at Auburn University, Alabama since 1990. Dr. Wentworth's research has focused on the high frequency characterization of materials used for electronics packaging. He is the author of Fundamentals of Electromagnetics with Engineering Applications (Wiley). Dr. Wentworth has received numerous teaching awards at Auburn University, including the Birdsong Merit Teaching Award in 1999. He is a Senior Member of the Institute of Electrical and Electronics Engineers (IEEE).

• Chapter 1 Introduction 11.1 Electromagnetic Fields 2Electric Fields 3Magnetic Fields 4Field Linkage 41.2 The Electromagnetic Spectrum 51.3 Wireless Communications 61.4 Dealing with Units 81.5 Working with MATLAB 10MATLAB Programs 151.6 Wave Fundamentals 191.7 Phasors 26Summary 29Problems 29Chapter 2 Transmission Lines 312.1 Distributed-Parameter Model 32Coaxial Cable 34Telegraphist’s Equations 372.2 Time-Harmonic Waves on Transmission Lines 39Characteristic Impedance 42Lossless Line 432.3 Power Transmission 452.4 Terminated T-Lines 48Voltage Standing Wave Ratio 50Input Impedance 51Complex Loads 53Special Terminations 542.5 The Complete Circuit 552.6 The Smith Chart 62Smith Chart Derivation 62Using the Smith Chart 69Impedance Measurement 732.7 Impedance Matching 76Quarter-Wave Transformer 78Matching with the Smith Chart 79Admittance of Shunt Stubs 81Shunt Stub Matching 842.8 Transients 87Pulse Response 91Practical Application: Schottky-Diode Terminations 95Reactive Loads 96Time-Domain Reflectometry 992.9 Dispersion 101Summary 107Problems 108Chapter 3 Electrostatics 1143.1 Vectors in the Cartesian Coordinate System 1153.2 Coulomb’s Law 122Electric Field Intensity 124Field Lines 1253.3 The Spherical Coordinate System 1263.4 Line Charges and the Cylindrical Coordinate System 129Infinite Length Line of Charge 133Ring of Charge 1383.5 Surface and Volume Charge 139Volume Charge 145Practical Application: Laser Printer 1483.6 Electric Flux Density 1493.7 Gauss’s Law and Applications 153Coaxial Cable 1573.8 Divergence and the Point Form of Gauss’s Law 1613.9 Electric Potential 166Gradient 1713.10 Conductors and Ohm’s Law 176Current and Current Density 178Joule’s Law 1813.11 Dielectrics 182Practical Application: Electret Microphone 1853.12 Boundary Conditions 1863.13 Boundary Value Problems 1903.14 Capacitance 194Electrostatic Potential Energy 198Practical Application: Electrolytic Capacitors 199Summary 200Problems 202Chapter 4 Magnetostatics 2084.1. Magnetic Fields and Cross Product 209Oersted’s Experiment 2144.2 Biot-Savart’s Law 214Solenoid 221Surface and Volume Current Densities 2224.3 Ampe`re’s Circuital Law 2244.4 Curl and the Point Form of Ampere’s Circuital Law 234Stoke’s Theorem 2364.5 Magnetic Flux Density 2374.6 Magnetic Forces 240Force on a Current Element 241Magnetic Torque and Moment 246Practical Application: Loudspeakers 2504.7 Magnetic Materials 2514.8 Boundary Conditions 2514.9 Inductance and Magnetic Energy 261Mutual Inductance 264Magnetic Energy 2664.10 Magnetic Circuits 269Electromagnets 273Practical Application: Maglev 276Summary 278Problems 280Chapter 5 Dynamic Fields 2865.1 Current Continuity and Relaxation Time 2865.2 Faraday’s Law and Transformer EMF 288Transformer EMF 290Transformers 293Point Form of Faraday’s Law 2955.3 Faraday’s Law and Motional EMF 296Generators 2995.4 Displacement Current 3015.5 Maxwell’s Equations 3055.6 Lossless TEM Waves 3065.7 Time-Harmonic Fields and Phasors 312Summary 315Problems 316Chapter 6 Plane Waves 3206.1 General Wave Equations 321Time-Harmonic WaveEquations 322Propagating Fields Relation 3276.2 Propagation in Lossless, Charge-Free Media 3286.3 Propagation in Dielectrics 330Low-Loss Dielectrics 332Loss Tangent 3336.4 Propagation in Conductors 335Current in Conductors 3376.5 The Poynting Theorem and Power Transmission 342UPW Power Transmission 3446.6 Polarization 347Practical Application: Liquid Crystal Displays 3526.7 Reflection and Transmission at Normal Incidence 353General Case 353Standing Waves 3586.8 Reflection and Transmission at Oblique Incidence 359TE Polarization 360TM Polarization 366Summary 368Problems 370Chapter 7 Waveguides 3737.1 Rectangular Waveguide Fundamentals 374Wave Propagation 377Waveguide Impedance 381Practical Application: Microwave Ovens 3847.2 Waveguide Field Equations 385TM Mode 388TE Mode 3947.3 Dielectric Waveguide 398TE Mode 401TM Mode 403Field Equations 4047.4 Optical Fiber 407Numerical Aperture 410Signal Degradation 411Attenuation 412Graded-Index Fiber 4137.5 Fiber-Optic Communication Systems 413Optical Sources 414Optical Detectors 416Repeaters and Optical Amplifiers 417Connections 4187.6 Optical Link Design 419Power Budget 419Rise-Time Budget 420Summary 423Suggested References 424Problems 424Chapter 8 Antennas 4268.1 General Properties 428Radiated Power 428Radiation Patterns 429Directivity 431Impedance and Efficiency 436A Commercial Antenna 4458.2 Electrically Short Antennas 438Vector Magnetic Potential 438The Hertzian Dipole 441The Small Loop Antenna 4458.3 Dipole Antennas 447Derivation of Fields 448Antenna Properties 451Half-Wave Dipole 4588.4 Monopole Antennas 462Image Theory 462Antenna Properties 463Practical Considerations 4658.5 Antenna Arrays 467Pair of Hertzian Dipoles 469N-Element Linear Array 473Parasitic Arrays 4758.6 The Friis Transmission Equation 476Polarization Efficiency 476Receiver Matching 4838.7 Radar 484Doppler Frequency Shift 4868.8 Antennas for Wireless Communications 487Parabolic Reflectors 488Patch Antennas 489Slot Antennas 490Folded Dipole Antennas 491Summary 492Suggested References 494Problems 494Chapter 9 Electromagnetic Interference 4999.1 Interference Sources 500Lightning 500Electrostatic Discharge 500Power Disturbance Sources 501Radio Transmitters 5029.2 Passive Circuit Elements 503Conductors 503Resistors 506Inductors 510Capacitors 5139.3 Digital Signals 5179.4 Grounds 519Bond Wires 521Signal Grounds 521Loop Area 5249.5 Shields 524Shielded Cable 5319.6 Filters 531Reflective Filters 531Ferrite Chokes 537Summary 538Suggested References 539Problems 540Chapter 10 Microwave Engineering 54110.1 Microstrip 543Attenuation 549Other Planar T-Lines 55010.2 Lumped-Element Matching Networks 55110.3 Scattering Parameters 557Reciprocal Networks 562Lossless Networks 563Return Loss and Insertion Loss 564Shift in Reference Plane 565The Vector Network Analyzer 56710.4 Couplers and Dividers 568Circulators 568Three-Port Dividers 570Couplers 57110.5 Filters 576Simple Filters 579Multisection Filters 581High-Pass Filters 586Bandpass Filters 58810.6 Amplifiers 592Designing Matching Networks 596Balanced Amplifiers 60010.7 Receiver Design 602Oscillators 602Mixers 603Microwave CAD 605Practical Application: Radio Frequency Identification 606Summary 607Suggested References 608Problems 609Appendix A Vector Relations 614Appendix B Coordinate System Transformations 617Appendix C Complex Numbers 621Appendix D Integrals, Conversions, and Constants 623Appendix E Material Properties 625Appendix F Common MATLAB Math Functions 627Appendix G Answers to Selected Problems 628Index 650