This paper introduces an improved transmission line NL-L (N ?? Z+, >2) de-embedding methodology by providing more stable and accurate transmission line characteristics, such as, Z0, phase and attenuation constants. More accurate results are achieved by using a deterministic matrix decomposition technique and also a more accurate ??-based circuit modeling of the parasitics for the probing pad adapters. Electromagnetic simulations (EM) and measurement results show that the inclusion of the improved parasitic model result in significantly more accurate de-embedding at mm-wave frequencies.