In this work, some modal techniques for solving guided-wave problems have been developed and implemented. Waveguides are very popular in the microwave industry because of their high power handling capability. The modal analysis of the fields in guided-wave structures permits to decompose a complex device in several simpler elements, which can be analyzed by the best suited method. Basically, modal techniques can be divided among those which analyze waveguide junctions and those which analyze the propagation characteristics of a given waveguide. Then, the application of the generalized circuital theory permits to join those structures properly. An analysis of the bibliography in this subject has been performed. The techniques that have been considered to be best suited for each problema have been implementated, and they have been generalized to N-furcated junctions, which are an extension of the bifurcated waveguides. In those cases where the geometry does not allow an analytic treatment, an hybrid technique finite element/modal analysis has been used. With the aid of these tools, some microwave devides have been designed and their performance has been validated with the aid of commercial simulators. Some guidelines for future work in the matter have been proposed.