Computer aided design of reentrant coaxial filters including coaxial excitation

An advanced EM based CAD tool is used for the detailed characterisation of a family of reentrant coaxial waveguide filters. The EM analysis includes the effects of tuning screws and of the input/output coaxial excitation. The software is essentially used as an efficient replacement for the traditional experimental characterisation procedure. As a result, design curves are obtained relating relevant electrical parameters to normalised structural dimensions. In addition to the theory, a four-pole filter structure has been built and tested demonstrating very good agreement between simulations and measurements.