Theoretical performance of the overmoded right-angle corner

This potentially important component in overmoded waveguide is examined by a diffraction analysis, and by a cruder mirror analysis. A general symmetry relation for the corner is deduced, and the diffraction analysis, but not the mirror analysis, is shown to satisfy it. Nevertheless, they both give similar numerical values for the scattered modes, though the former indicates somewhat larger values. The diffraction method is beset with difficulties arising near shadow edges from the corners, and although this is overcome in the mutual-illumination part of the analysis, it reappears in the resulting calculation of the radiation into the guide. This part of the solution fails, in any case, for the modes near cut off, and is unusable beyond. A 10in guide with corner mirror is calculated to have a transmission loss of 0.9dB at 4.2GHz, and 0.2dB at 40GHz. Most of the loss appears in the lower-order forward-scattered modes.