Q-factor measurements of open resonators in the millimeter-wave range including coupling losses

The unloaded quality factor as well as the coupling coefficient of open resonators are determined by evaluating measured complex reflection coefficients. The cavity is described by an equivalent circuit, the parameters of this circuit are calculated by means of a least-square fit of the simulated to the measured reflection coefficients. The solution is obtained using the Householder-algorithm, which promises very fast and stable computation. This approach is capable of evaluating quality-factor measurements for each type of resonator, even with losses in the coupling aperture. Its validity is illustrated by measurements in the cm- and mm-wave range.