Error Analysis for Waveguide-Bridge Dielectric-Constant Measurements at Millimeter Wavelengths

The use of the free-space waveguide-bridge dielectric-measurement technique is demonstrated for accurate complex-permittivity measurements at millimeter wavelengths. An error analysis is presented for applications of this technique with the sample rotated in the plane of incidence in order to avoid coupling between the sample and the horns, and to minimize the effects of multiple reflections from the two air/dielectric interfaces. Data are presented for slip-cast fused silica at 94 GHz to demonstrate the accuracy of the technique and to verify the error analysis.