Measurement of the complex dielectric constant down to helium temperatures. I. Reflection method from 1 MHz to 20 GHz using an open ended coaxial line

The reflection off an open ended coaxial probe pressed against a material u nder test is used to determine the complex microwave (1 MHz-20 GHz) dielect ric response of the material. A full-wave analysis of the aperture admittan ce of the probe, in terms of the dielectric properties of the backing mater ial and the dimensions of the experimental geometry, is given. We discuss t he calibration procedure of the setup and present the complex dielectric re sponse of several materials determined from the measured reflection coeffic ient. The results obtained with the open ended coax interpolate well betwee n data taken at lower and higher frequency bands using different experiment al methods. We demonstrate that this method can be applied to perform diele ctric measurements at cryogenic temperatures. (C) 2000 American Institute o f Physics. [S0034-6748(00)04802-4].