Least-square estimation of the equivalent circuit parameters of a via-hole from a TDR reflectogram, including on-board rise time and delay estimation

Two different time-domain reflectometry (TDR)-based methods for estimating the equivalent circuit parameters of a via hole are presented. The first method is semigraphical, the second is a numerical estimation technique. Estimation is not restricted to equivalent circuit parameters, but onboard unknown rise times and delays are also included. Two possible models for a via hole are compared: a single capacitor model and a pi -network, with two capacitances and an inductance. For certain categories of via hole, the inductive component turns out to be rather important.>