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66 DESIGN007 MAGAZINE I AUGUST 2018 microstrip line, two pairs of back-drilled vias, 1.5" of stripline and four press-fit connectors and launches to do the measurements. The vias, trace size and shapes are adjusted to match the actual manufactured structures (remember, the boards are not manufactured as designed). The dielectric and conductor roughness models are identified with S-param - eters measured for two differential microstrip and two differential stripline segments using the generalized modal S-parameters (GMS- parameters) technique with proper loss dielec - tric and conductor loss separation (see details in the paper). As shown in Figure 2, the anal- ysis-to-measurement correlation in frequency domain was acceptable up to 30 GHz and TDR Figure 2: Analysis-to-measurement correlation in frequency domain is acceptable up to 30 GHz. Figure 3: The correlation is used to reliably predict the eye diagram for the 28 Gbps NRZ signal.