Simulated scalar feed horn antennas are found to be exhibiting identical radiation characteristics of metallic corrugated feed horn antennas of same dimensions. Hence, in this paper, the e-plane radiation characteristics of a simulated scalar feed horn antenna is analyzed theoretically by extending the theory of metallic corrugated horn antennas. The theoretical e-plane radiation patterns at different frequencies in X-band are compared with that of experimentally obtained e-plane radiation patterns. Even though the nulls of the radiation patterns are not fully realized by the theory, the main beam characteristics are well explained.