An accurate broadband measurement of substrate dielectric constant

An improved two-microstrip line method is proposed for a simple and accurate measurement of the dielectric constants of substrates, The errors due to the transition mismatches and connection repeatability are removed by using the selection algorithm of the best data set in multiple measurements, based on the minimum error cost concept, The measurement data for CGP-500 substrate in broad frequency range (0.5-25.5 GHz) are shown and the result agrees quite well with the theoretical one.