Multi-step slow-wave systems have found a number of applications in microwave techniques. Specifically, insignificant modification of conventional (single-step) slow-wave systems provides an opportunity of their dispersion properties control. The existence of fast waves in such systems opens up additional opportunities of their implementation in quasi-optical devices and antenna techniques.

The studies of multi-step slow-wave systems can be carried out by the analysis of the radiation field formed by such a system under different ways of excitation. The report presents consideration of directional radiation patterns of the open multi-step comb-type slow-wave system excited by a waveguide connected to one of its grooves. The analysis was based on the exact solution of the excitation problem obtained earlier [1-3].