MEASUREMENT OF DIELECTRICS AT 100-GHZ WITH AN OPEN RESONATOR CONNECTED TO A NETWORK-ANALYZER

A high-Q hemispherical open resonator is connected to an automatic net work analyzer to enable precise and fast determination of the permitti vity and loss tangent of low-loss dielectric materials at 100 GHz. Bot h scalar theory and vector theory with a frequency variation method ar e used to determine the dielectric properties of low-loss materials wh ich are used in quasioptical components, for example in fusion reactor windows and lenses for millimeter-wave receivers, The uncertainty of the measurement is 0.02% to 0.04% for epsilon'(r) (epsilon(r) greater than or equal to 2) and 6 - 40 x 10(-6) for tan delta (10(-4) less tha n or equal to tan delta less than or equal to 10(-3)).