LTCC Dielectric Constant and Loss Tangent Extraction by Thru-Line Method in Stripline

摘要

Stripline can support pure TEM mode propagation but its signal trace is embedded inside substrate. GSG probe pad, microstrip line and via transitions are designed to allow GSG probing on substrate surface to measure S-parameters of stripline. The mismatch of transitions are removed by thru-line method to yield complex propagation constant of stripline. As propagation constant is measured, the εr and tanδ of the substrate can be calculated by closed-form equations. Measurement results of a low εr and low loss LTCC substrate show that longer LINE circuits can give more stable results in εr and tanδ.