Frequency (GHz)Fig. 1. The extracted inductance of a spiral inductor as a function of reference impedance. • No ren orm. • l ref = 20 ... Z = Z -5% ref 0 • Z = Z + 5% ref 0 Zref = Re 2 0 2.5 4.5 I 4 cThe only method that does not need the characteristics of the reflection calibration standards is the Thru-Reflect-Line (TRL) method [6], [7]. However, the reference impedance in the TRL calibration corresponds to the characteristic impedance of the lines used in the calibration. This in general complex impedance is usually not known. In Fig. 1 the influence of the reference impedance on the extracted inductance of a single layer spiral inductor is shown. If we use the Y 11 -based definition of the inductance L = Im(Yii 1 ) / w we get(1 -8 11 )(1 + 8 22) + 8 12821where 8 i j are the S-parameters referenced to Zo impedance. This means that the accuracy of the inductance determination is directly proportional to the impedance accuracy. Thus, the accurate determination of the complex characteristic impedance is of great importance, since this value determines the accuracy of the RLCG-parameter de-embedding. Moreover, Abstract-Accurate determination of the characteristic impedance determines the accuracy of the characterization of transmission lines and passive devices. In this paper, we present a novel, time-domain based procedure for the complex characteristic impedance determination. The method is insensitive to changes in the reference plane and the parasitic shunt admittance at the probe tips. For highly accurate passives characterization, a modification of the Thru-Refleet-Line (TRL) calibration algorithm is proposed. It enables the use of the TRL method to deembed components having the ports on different metallization levels. Additionally, a comprehensive overview and evaluation of both frequency and time-domain methods for characteristic impedance determination is included for completeness. We present measurement results of transmission lines and spiral inductors fabricated in MCM-D technology on low-and highresistivity substrates up to 65 GHz.