This text delves into the operation of the physical layer of modern wireless communication systems, including cell phones and wireless local area networks. Beginning with basic electromagnetism and probability theory, this book explores antenna design and the interference that waves encounter as they propagate through cities, inside buildings, or to and from satellites. It examines the physics of Geostationary Earth Orbiting and Low Earth Orbiting satellites to evaluate first-order designs of SATCOM systems. It also offers an historical view of wireless communications. Designed as a textbook for senior undergraduates or first year graduate students, this volume also serves as a useful reference for engineers in the wireless communications industry.