This book explores the fundamentals of electromagnetic fields and waves, focusing on passive linear devices used in antenna-feeder systems and fiber-optic communication lines. It provides insights into analysis methods, technical specifications, and design features of such components, including regular waveguides and microwave devices. Designed for university students studying "Design and Technology of Radio Engineering Systems" (specialization 210200) and "Design and Technology of Electronic Devices" (specialization 211000), it serves as a comprehensive resource for understanding these essential elements of modern radio and communication technology.