Validation Methods for S-parameter Measurement Based Models of Differential Transmission Lines

Signal Integrity engineers are typically simulating systems using simulation models and measuring signals in systems using instruments. Often, during the design process, simulated models are replaced with measurement based models – those typically generated using a VNA or TDR. There is often confusion during this process for two reasons. First, the measurement based models often look different than the simulation models. Second, the measurement based models and simulation based models produce different waveform results in simulation. This is compounded by the fact that systems nowadays are usually differential. Engineers need some insight to validate measurement based models. This paper provides basic information on how to interpret s-parameter based models and how to create reasonable expectations on the measurement methods and on the models performance. It also provides methods to tie simulation and measurement together to validate models through time-domain co-simulation – the process of mixing real measurements and simulation techniques