Broadband Dielectric Measurement Of LCP Substrate Materials By Differential Phase Length Method

Liquid crystal polymer (LCP) is a material that has gained attention as a potential microwave and millimeter-wave substrate and package materials. The differential phase length method has been proposed to determine the dielectric constant of LCP substrate ranging 10MHz-40GHz. In this paper, the results shown that the dielectric constant keeping stable in a bandwidth frequency is about 3.2, and the measurement can be strongly affected by transition of probe-to-GCPW in the test circuits. Meanwhile, the improvement result for the circuits with the difference length of 20 mm is obtained, whose dielectric constant with a little changing in a wide band range.