I. Introduction
High frequency measurement of transmission line structures is critical to characterization and development of signal integrity analysis in high speed digital circuits. Due to measurement features, transmission lines are customarily embedded into test fixtures to allow pre-requisite interfaces for measurements. However, the discontinuities introduced by test fixture (e.g. connectors, vias) are usually an unavoidable challenging for designers [1] [2]. Therefore, de-embedding is an indispensable procedure for obtaining the scattering parameters (S-parameters) of a device under test (DUT) transmission line. Although classic calibrations could be performed (SOLT, TRL, LRM, LRRM) for removing undesired test fixtures, these often require a number of precisely designed and manufactured patterns, which consume precious design space as well as measurement time. Numerous calibration patterns also require that each interconnect between measurement instruments and DUTs maintain consistency, which is a challenge—particularly in modern micro-probing application where different landing locations may introduce discrepancies into de-embedded results. For reducing the amount of calibration patterns, modeling equivalent lumped circuit [3]–[5] or equivalent networks, such as open-short [6], [7] and NL-L [8] of test fixtures are a mainstream on-going research topic for transmission line de-embedding. Typically, most of them are either assuming that test fixtures are electrically small or putting unrealistic physical design constraints.