A General Computer Program for Precise Calculation of Dielectric Properties from Short-Circuited Waveguide Measurements

Principles underlying the short-circuited-waveguide measurement method and a general computer program for precisely calculating dielectric properties of materials from such measurements are described briefly. The program facilitates the use of the widely applicable short-circuited-line technique for accurate work with high-loss as well as low-loss materials. The program is applicable to measurements taken on coaxial lines or on rectangular or circular-waveguide systems. Corrections are included for the influence of the slot in slotted-waveguide sections, and differences in the velocity of propagation in air and in a vacuum are taken into account. If these factors are ignored, errors of about 0.5 percent in the determination of the dielectric constant may result Corresponding errors in the dielectric-loss-factor and loss-tangent values can range up to 2 or 3 percent. Much greater errors result when certain approximations that are valid for low-loss materials are used for calculations on materials of higher loss. The program described avoids these problems through use of the general complex equations and exact relationships. Other general characteristics of the program include flexibility in the character and range of acceptable input data.