The development of a microwave system relies on CAD tools that are both accurate and fast. Through the use of computers, a set of theoretical tools can form the basis for efficient CAD tools for the design of modern microwave systems. This text aims to explain and analyze modern multimodal techniques for the design of waveguide components based on multimodal equivalent network representation. Divided into three sections, the book covers modal analysis of waveguides and cavities; presents a number of basic waveguide junctions and describes specific applications. Applications based software (supplied on disk) relevant to each section, is available with the book. This should assist readers to develop CAD tools, and provides executable programs compatible with each section of the book, allowing them to input their own data.