Waveguide sections are now widely used both for commercial and military purposes. The trend of investigations in this field is to decrease the insertion loss and overall dimensions of microwave devices. But if high power of propagating waves is required (100W or more) it is impossible to use waveguide circuits based on the dielectric discontinuities or semiconductor active devices. In such a case the metal discontinuities (irises, plates, posts etc.) become alternatives. Metal plates are especially easy to manufacture and maintain into metal waveguide. The possibility of creation of phase shifters with excellent parameters on the base of such type of discontinuities was shown in [5].

This paper presents new results of FDTD analysis of such structures well described in [1, 2]. Actually, it’s hybrid method combining the implementation of impedance boundary conditions to standard FDTD technique with generalised scattering matrix modelling. This algorithm proves its efficiency for rigorous analysis of different types of complex waveguide discontinuities.