This book is based on the author’s nearly two decades of theoretical research in “signal integrity” and his experience accumulated in engineering design practice. It elaborates on the fundamental theory and design knowledge of “signal integrity” required for designing high-speed digital circuits, including relevant basic concepts, causes of problems, understanding and analysis methods, design countermeasures, and the technological evolution process. The book employs language that is as simple, straightforward, and comprehensible as possible to explain technically intricate and complex issues. Without any complex or lengthy mathematical derivations, the book uses simple dialogue-style explanations as well as visual and direct diagrams to analyze problems.