Two-dimensional diffracted fields from semiinfinite conducting plane with a circular cylinder of various types at its apex are studied for the purpose of suppressing the backward radiations from the reflector antennas. The basic policy for the suppression of the diffracted fields was already obtained by the authors. It concludes that the electrically and magnetically conducting cylinders are most effective in suppressing the diffraction for the E and H wave incidence, respectively. From the practical point of view, the main difficulty in this policy is how to realize the magnetically conducting cylinder which suppresses the H wave diffraction. In this paper, a corrugated cylinder is adopted for the purpose of the suppression of the H wave diffraction. The characteristics of this cylinder are analyzed by the mode-matching techniques and it is indicated that the corrugated cylinder fairly suppresses the diffracted fields, not only for the H wave but also for the E wave incidence, to almost the optimal level. Additionally, the wideband frequency characteristics are introduced. All these theoretical results are confirmed by the equivalent two-dimensional experiments. At the end of this paper, the applicability of the corrugated cylinder to the suppression of the three-dimensional diffracted fields is suggested experimentally.