Some electromagnetic aspects of microwave filter design

There are two approaches to the problem of frequency selective device synthesis: the traditional one based on circuit theory, using the numerical solutions of boundary value problems only at the stage of the reconstruction of filter element geometry according to the requirements on its single-mode S-matrix; and a relatively new method based on methods of numerical optimization. However, there are some specific procedures that generate an intermediate way combining the wide intellectual basis of the first approach and the high accuracy of the second. The authors discuss such a technique for the design of waveguide band-pass filters.