An approximate generalization of Schelkunoff's horn-gain formulas

Schelkunoff's (1943) classical horn-gain formulas are applicable only to pyramidal and H-plane sectoral horns, which satisfy the Kirchhoff approximation. In this paper, a general gain formula is proposed that would be applicable also to E-plane sectoral horns and open-ended rectangular waveguides. The new formula is obtained by incorporating the "edge effect" into the classical formulas. Whereas for large apertures the new solution gives the same values as the conventional formulas, for small apertures it gives significant improvement over them and compares well with other improved gain formulas.