Radio Wave Propagation Fundamentals

Artem Saakian

A R T E C H H O U S E BOSTON|LONDON a r techhouse .com

Contents

Preface XI

CHAPTER 1

Inroduction

1.1 Historical Overview 1.2 Classification of Radio Waves by Frequency Bands 1.3 The Earth's Atmosphere and Structure 1.4 Classification of Radio Waves by Its Propagation Mechanisms 1.5 Interferences in RF Transmission Links

Problems References

1

1 3 5

10 14 17 18

CHAPTER 2

Basics of Electromagnetic Waves Theory 21

2.1 Electromagnetic Process 21 2.1.1 Maxwell's Equations of Electrodynamics 21 2.1.2 Boundary Conditions of Electrodynamics 25 2.1.3 Time-Harmonic Electromagnetic Process—Classification

of Media by Conductivity 30 2.2 Free Propagation of Uniform Plane Radio Waves 34

2.2.1 Uniform Plane Wave in Lossless Medium 38 2.2.2 Uniform Plane Wave in Lossy Medium 39

2.3 Polarization of the Radio Waves 45 2.4 Reflection and Refraction of Plane Radio Wave from the

Boundary of Two Media 49 2.4.1 Normal Incidence on a Plane Boundary 51 2.4.2 Oblique Incidence of Vertically Polarized Radio Wave 53 2.4.3 Oblique Incidence of Horizontally Polarized Radio Wave 56 2.4.4 Reflection of the Radio Wave with Arbitrary Polarization 57 2.4.5 Power Reflection and Transmission 58 2.4.6 Reflection of the Radio Wave from the Boundary of

Nonideal Dielectric Medium 60 2.5 Radiation from Infinitesimal Electric Current Source: Spherical Waves 61 2.6 Spatial Area Significant for Radio Waves Propagation 63

2.6.1 Principle of Huygens-Kirchhoff 63 2.6.2 Fresnel Zones 65 2.6.3 Knife-Edge Diffraction 70 2.6.4 Practical Applications of the Fresnel Zones Concept 75

VII

Contents

Problems 80 References 84 Appendix 2A Useful Mathematical Relations 84 Appendix 2B Polarization of Radio Waves 87 Appendix 2C Basic Relations in Infinitesimal Electric Current Source

Radiation Analysis 94 Appendix 2D Frsenel's Integrals 102

CHAPTER 3

Basics of Antennas for RF Radio Links 105

3.1 Basic Parameters of Antennas 105 3.1.1 Radiation Pattern and Directivity 105 3.1.2 Radiation Resistance and Loss Resistance 111 3.1.3 Antenna Effective Length and Effective Area of

the Aperture 113 3.2 General Relations in Radio Wave Propagation Theory 117

Problems 122 References 124

CHAPTER 4

Impact of the Earth Surface on Propagation of Ground Waves 125

4.1 Propagation Between Antennas Elevated Above the Earth's Surface: Ray-Trace Approach 125 4.1.1 Flat Earth Approximation Case Study 126 4.1.2 Propagation over the Spherical Earth Surface 134 4.1.3 Specifics of Propagation over a Rough

and Hilly Terrain 143 4.1.4 Optimal Path Clearance and Choice of the

Antenna Elevations 147 4.1.5 Propagation Prediction Models in Urban, Suburban,

and Rural Areas 149 4.2 Propagation Between Ground-Based Antennas over the Flat Earth 159

4.2.1 Antennas over the Infinite, Perfect Ground Plane 160 4.2.2 Leontovich Approximate Boundary Conditions and

Structure of Radio Waves Near the Earth's Surface 163 4.2.3 Propagation over the Real Homogeneous Flat Earth 169 4.2.4 Propagation Along the Real Inhomogeneous

Flat Earth: Coastal Refraction 173 4.3 Asymptotic Diffraction Theory of Propagation over the

Spherical Earth Surface 178 4.3.1 Basic Concepts 178 4.3.2 Propagation Between Ground-Based Antennas 183 4.3.3 Propagation Between Elevated Antennas 189 4.3.4 Specifics of Propagation Estimates in Penumbra Zone 191 Problems 196 References 197

Contents

Selected Bibliography 198 Appendix 4A Input Impedance of the Radiating Current

Element Above the PEC Ground Plane 199 Appendix 4B Diffraction of Radio Wave Around Earth's

Surface: Basic Theory 202

CHAPTER 5

Atmospheric Effects in Radio Wave Propagation 21 3

5.1 Dielectric Permittivity and Conductivity of the Ionized Gas 213 5.2 Regular Refraction of the Radio Waves in the Atmosphere 218 5.3 Standard Atmosphere and Tropospheric Refraction 220 5.4 Reflection and Refraction of the Sky Waves in the Ionosphere 225 5.5 The Impact of Earth's Magnetic Field on Propagation of the

Radio Waves in the Ionosphere 231 5.5.1 Longitudinal Propagation of the Radio Wave 233 5.5.2 Transverse Propagation of the Radio Wave 237 5.5.3 Propagation of the Radio Wave Arbitrary Oriented

Relative to the Earth's Magnetic Field 239 5.5.4 Reflection and Refraction of Radio Waves in the

Magneto-Active Ionosphere 242 5.6 Over-the-Horizon Propagation of the Radio Waves by the

Tropospheric Scattering Mechanism 244 5.6.1 Secondary Tropospheric Radio Links 244 5.6.2 Analytical Approaches in Description of the Random

Tropospheric Scatterings 246 5.6.3 Physical Interpretation of Tropospheric Scatterings 251 5.6.4 Effective Scattering Cross-Section of the Turbulent

Troposphere 254 5.6.5 Statistical Models of Tropospheric Turbulences 255 5.6.6 Propagation Factor on Secondary Tropospheric Radio Links 261 5.6.7 The Specifics of the Secondary Tropospheric Radio Links

Performance 266 5.7 Attenuation of the Radio Waves in the Atmosphere 271

5.7.1 Attenuations in Troposphere 271 5.7.2 Attenuations in Ionosphere 275 Problems 282 References 284 Appendix 5A Volumetric Spectrum for Autocorrelation

Function of Statistically Homogeneous and Isotropic Random Field 285

CHAPTER 6

Receiving of the Radio Waves: Basic Outlines 287

6.1 Multiplicative Interferences (Signal Fades) 287 6.1.1 Fluctuation Processes and Stability of Radio Links 287 6.1.2 Fast Fading Statistical Distributions 293

Contents

6.1.3 Slow Fading Statistical Distribution 302 6.1.4 Combined Distribution of Fast and Slow Fades 307

6.2 Additive Interferences (Noises) 314 6.2.1 Internal Noises of One-and Two-Port Networks 314 6.2.2 Noise Figure and Noise Temperature of the Cascaded

Two-Port Networks 317 6.2.3 Noise Figure of the Passive Two-Port Networks 319 6.2.4 Antenna Noise Temperature 322 6.2.5 Receiver Sensitivity and Signal Threshold Definition 323 6.2.6 Environmental (External) Noise 325

6.3 Methods of Improvement of the Radio Wave Reception Performance 333 6.3.1 Noise-Suppressing Modems in Analog CW Systems 334 6.3.2 Use of Spread-Spectrum Discrete Signals 336 6.3.3 Diversity Reception Technique 340 Problems 346 References 348 Selected Bibliography 349

List of Symbols 351

Acronyms 355

About the Author 357

Index 359