The effect of flanges on the radiation patterns of waveguide and sectoral horns

Measurements are given of radiation patterns of open-ended rectangular waveguide with conducting flanges attached to the long edges of the aperture. In particular, the considerable effect of different flange lengths and included angles on the E-plane patterns is examined; these measurements are made at three frequencies in order to supplement data, already published, describing measurements made at a single frequency. A suggestion that the E-plane radiation pattern can be approximated by the radiation pattern of a primary source and two secondary sources near the end of the flanges has been substantiated if a suitable obliquity factor is assumed. Some E-plane patterns of flanged H-plane sectoral horns are also given. It is found that there are differences between these patterns and those of similarly flanged waveguide. The effect of flanges on the H-plane patterns of an E-plane sectoral horn is comparatively small, as was expected.