Field theory analysis of rectangular and circular waveguide discontinuities for filters, multiplexers and matching networks




Varailhon de la Filolie, Benoît

Journal Title

Journal ISSN

Volume Title



Progress in integrating microwave circuits depends largely on the development of computationally effective and accurate numerical methods. These methods allow a miniaturization of microwave components and their utilization at higher frequency. In this thesis, the application of the mode matching method is described as well as their modification to different kinds of structure in rectangular and circular waveguides. The task is to design and optimize filters, multiplexers and impedance matching networks. In its most general form, the mode matching method at waveguide discontinuities requires the matching of four field components. However, to improve computational efficiency, the effect of matching only two field components (versus four field components) is investigated and successfully exploited for selected discontinuities. To satisfy space requirements, low loss, compact, and lightweight diplexer, triplexer and quadriplexer structures in rectangular waveguide technology are designed and optimized. The analysis is made possible by decomposing the structure into simple discontinuity sections such as discontinuity in width, height or bi- and tri-furcations. Three different types of discontinuities in coaxial waveguide are investigated: the outer step, the inner step and the gap discontinuities. By cascading such discontinuities, filters or matching networks can be obtained. Finally, a new type of circular waveguide bandpass filter using printed metal inserts is developed and designed in Ka-band. A comparison between theoretical results and measurements shows excellent agreement.



Electric filters, Wave-guide