Reflection Coefficient of Unequal Displaced Rectangular Waveguides (Letters)

The IEC has suggested that maximum allowable displacements of waveguide flanges should not cause the inherent return loss due to waveguide tolerances to degrade more than 1 dB. Calculations on displaced unequal waveguides at their extreme tolerances show that this leads to a maximum allowable displacement of 0.0175 of the broad (= a) dimension for a waveguide tolerance of ± a/500. The worst return loss under these conditions is approximately -41dB. However, it is suggested that this maximum allowable displacement is based on a statistically remote worse case condition, and relaxation to a value of 0.021a would be more realistic.