Measurement of Dielectric Loss and Wall Loss in a Dielectric-Filled Waveguide

A waveguide bridge capable of measuring dielectric loss down to 5 μrad at frequencies of 10-35 GHz is described. A major uncertainty was the value of the wall loss. This has been resolved by measuring the wall loss of the specimen arm both with air and dielectric filling. The results demonstrate that the wall loss of a dielectric-filled waveguide can be calculated from the theoretical expression corrected by a factor which is the ratio of observed to calculated loss for an air-filled guide. The uncertainty in the determination of dielectric loss is reduced to at most a few microradians.