Precision Determination of the Dielectric Properties of Nonmagnetic High-Loss Microwave Materials

Abstract

New tests by the author to determine the, dielectric properties of high-loss nonmagnetic microwave materials used for waveguide absorbers and anechoic chamber linings reveal two significant results: dielectric parameters may be calculated from simple formulas without solving transcendental equations, and accuracy is limited only by the homogeneity of the sample and the precision of its fit in the waveguide. The technique used is based upon prior work by other researchers but is refined for materials with loss tangents exceeding 0.1. These previously have received little attention in the literature. Results of tests in the S-band yield loss tangents between 0.4 and 0.8, and dielectric constants from 1.5 to 2.0 for samples completely filling the cross section of WR284 waveguide. The author reviews other methods, analyzes error sources, and describes his laboratory work.