Microwave Vacuum Electronic Devices (VEDs) encompasses VEDs operating in the microwave to terahertz frequency regime. The book aims to equip students, teachers, scientists, and engineers with an understanding of the concepts and physical principles underpinning VEDs. VEDs have manifold applications for technologies used in the defence, civilian, medical, scientific, and industrial sectors. The authors build confidence among the readers seeking to design and develop VEDs in these sectors by presenting the enabling concepts and step-by-step guides to the mathematical formulations used in VEDs in the microwave, millimeter-wave and terahertz frequency range. Chapters covering important physical principles, including space-charge waves, cyclotron waves, and electron bunching (both relativistic and non-relativistic), are followed by discussions of techniques for improving the performance of VEDs. The book will be a useful reference for advanced undergraduates, postgraduates and industry professionals seeking to understand and develop their own VEDs.Key Features:Discusses practical concepts that enable readers to develop independent thinking in the design and development of VEDs.Provides detailed mathematical steps that make the design and development of VEDs easier to understand.Presents end-of-chapter questions and hints throughout to aid teaching and learning.