This part of IEC 1580 gives the means for determining the reflection coefficient at the junction of two similar rectangular waveguides due to the following imperfections:
a) differences in the waveguide internal dimensions;
b) lateral displacement between the waveguide axes in either the H or E plane;
c) angular misalignment between the waveguide axes.
IEC 61580-9:1996 history
1996IEC 61580-9:1996 Methods of measurement for waveguides - Part 9: Reflection coefficient at rectangular waveguide interfaces