Parameter Extraction of Coaxial via for Printed Circuit Boards with Reflection Measurement in Probing Approach

This paper shows the parameter extraction of the coaxial via (CV) used in printed circuit boards (PCBs), including the propagation constant and characteristic impedance, by using reflection coefficient measurements of four test structures in probing approach. In this study, the stack-up of the PCB is in six layers where the CV is arranged from layer-3 to layer-6 and layer-1 to layer-3 are used as the transition of the CV to the planar transmission line (TL). By measuring the reflection coefficients of the short structures at layer-1/2/3, as well as the open-end pad at layer-6, the characteristic impedance and propagation constant of the CV can be evaluated by analytic expressions, respectively. The proposed method is verified by the measured dielectric constant of the material filled between the inner and outer conductors of the CV with the manufacturer's data in good agreement.