PREFACE

This textbook on radiowave propagation is designed for use at the college senior and first-year graduate school level. It should also be useful to practicing engineers, particularly antenna and telecommunication systems engineers, who need a good understanding of propagation but may not have had sufficient exposure to this subject. The number of antenna courses taught in American universities seems to exceed greatly the number of propagation courses; this text is intended to encourage more radiowave propagation course offerings.

We have tried to achieve a balance between the theoretical developments, that is, the physics of radiowave propagation, and the many applications. The theory is necessary for a thorough understanding of the propagation phenomena and, especially, the limitations of various methods for predicting system performance. Although the discussions of applications are intended to be useful in themselves, they also contribute to the general understanding. A broad spectrum of applications is considered, as opposed to focusing only on a specific technology, such as cellular systems. Of course, a text of this size cannot cover all applications in complete detail. Fortunately, the recommendations of the Radiocommunication Sector of the International Telecommunication Union (ITU-R) are a repository of the currently recommended practices, and the student is often referred to these recommendations for details beyond the scope of this book.

In writing this book, we have reviewed some basic material that is all too often slighted in courses on electromagnetic theory and antennas. For example, in treating the behavior of dielectrics, electromagnetic theory courses often proceed very quickly to free space or very simple media to lay the groundwork for antennas and transmission lines. However, radiowave propagation media often are not simple: they can be anisotropic, inhomogeneous, lossy, dispersive, and time varying. Therefore, Chapter 2 treats dielectrics with such properties in mind. Similarly, Chapters 3 and 4 review plane wave theory and antenna and noise concepts from the propagation point of view. Chapter 6 reviews basic refraction and reflection concepts before applying them to propagation over terrain. In the same spirit, Chapter 8 includes a brief introduction to the probability theory concepts necessary to characterize fading.

Since the late 1950s, courses in Radiowave Propagation have been given regularly at The Ohio State University (OSU). An initial set of course notes appeared in 1961 after one of the authors attended an intensive and well-documented three-week course given by the staff of the Central Radio Propagation Laboratory of the National Bureau of Standards in Boulder, CO. Needless to say, there have been many additions and changes over the years as new applications (e.g., satellite and cellular communications) and new tools (e.g., computer programs for ionospheric predictions) became available and others waned in importance and as the instructors for the course changed. Substantial changes were also made in converting the course notes into a book. Each of the authors has had experience in teaching the course. We are grateful to many generations of students for their comments and suggestions, and we look forward to the inputs of future generations.

We wish to express our appreciation to those who were especially helpful in the making of this book. A sabbatical year at the National Center for Atmospheric Research as Senior Post-doctoral Fellow helped Prof. Levis broaden his understanding of atmospheric effects and research; he is indebted to many members of the staff, but especially to Dr. Ray Roble for insights into the dynamics of the upper atmosphere and to Dr. Pauline Middleton for general guidance and friendship. Later, most of a year as Invited Guest Worker at the Institute for Telecommunication Sciences (ITS) of the National Telecommunications and Information Administration (NTIA) was similarly stimulating, with access also to the staff of the National Geophysical Data Center (NGDC) of the National Oceanic and Atmospheric Administration (NOAA). Many staff members were helpful, but special thanks are due to Dr. James R. Wait, Dr. George Hufford, Dr. Hans Liebe, and Dr. Kenneth Allen at ITS and to Dr. Kenneth Davies and Mr. Ray O. Conkright at NOAA. Prof. Levis also acknowledges help from Reference Librarian Jean Bankhead. He is also grateful for the support and friendship of Alan and June Roberts who opened their home and their hearts to him.

Prof. Teixeira is grateful to the Department of Electrical and Computer Engineering of OSU for providing him with a sabbatical leave in 2009 for the completion of this book. We thank Ms. Lisa Stover of the OSU ElectroScience Laboratory (ESL) for editorial assistance and Ms. Mengyuan Guo, also of ESL, for help in the preparation of many of the figures. We also thank the staff at John Wiley & Sons, Inc., including our editor, George Telecki and his assistant, Lucy Hitz; production manager Danielle Lacourciere, and project manager Nitin Vashisht.

We are ever so grateful for the support of our wives and our families, and for their patience while we were preoccupied with teaching and writing.

Curt A. Levis
Joel T. Johnson
Fernando L. Teixeira