Thesis (M.A.)--Boston UniversityEssentially, this paper deals with the design and development of a specialized type of waveguide directional coupler commonly known as a hybrid. A preliminary discussion concerning Maxwell's Equations and the portion of the electromagnetic spectrum with frequencies from 1,000-30,000 megacycles, known as the microwave region, is presented as necessary background material. The phenomenon of skin effect and other undesirable complications present at these high frequencies is considered. As a solution to some of these problems, improved transmission lines in the form of coaxial cables and rectangular waveguide are treated at length; the emphasis being mainly on waveguides