Wireless communications are based on the launching, propagation, and detection of electromagnetic waves emitted primarily at radio or microwave frequencies. Their history can be traced back to the mid-19th century when James Clerk Maxwell formulated the basic laws of electromagnetism and Heinrich Hertz demonstrated the propagation of radio waves across his laboratory. Recent engineering breakthroughs have led to wireless communication systems that have not only revolutionized modern lifestyles, but have also launched new industries.Based on the author's course in the physics of wireless communications, "Physical Principles of Wireless Communications" provides students with a solid foundation in modern wireless communication systems. It offers rigorous analyses of the devices and physical mechanisms that constitute the physical layers of these systems. Starting with a review of Maxwell's equations, the textbook details the operation of antennas and antenna arrays, teaching students how to perform the necessary design calculations. It also explores the propagation of electromagnetic waves, leading to important descriptions of mean path loss. The text also reviews the principles of probability theory, enabling students to calculate the margins that must be allowed to account for statistical variation in path loss.In addition, it covers the physics of Geostationary Earth Orbiting (GEO) satellites and Low Earth Orbiting (LEO) satellites so students may evaluate and make first-order designs of satellite communications (SATCOM) systems.