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20 The PCB Design Magazine • October 2014 feature nector and then matched both magnitude and phase of the reflection and transmission of the measured S-parameters and the circuit model of the back-to-back structure [5] . In addition, mod- els for all launches (PCB part) were built with the 3D electromagnetic solver as a part of the post-layout electromagnetic decompositional analysis in Simbeor. That eliminated the error- prone de-embedding step. Technically, comparison of the magnitudes and phases of S-parameters is sufficient to either make a decision on the accuracy or spot a prob- lem. However, comparison in time domain is usually also needed and may reveal additional tion. This is due to large manufacturing and di- electric properties variations in the test fixtures typical for PCB realm. Thus, we proceed with the second option: validation for the complete link path. All mea- surements for the step 1 were done with the 2.92 mm SMA connectors and 2.92 to 2.4 coaxial adapters; no models were available for both. To overcome this obstacle, the model of the con- nector with the adapter was simply synthesized from S-parameters measured for two connec- tors and two adapters connected symmetrically back-to-back. We used cascaded connection of four coaxial sections to model adapter and con- SINk OR SWIM AT 28 GBPS continues Figure 5: Model-to-measurement validation results for microstrip link with two capacitive vias (Figure 1, structure 1): Magnitudes of the transmission and reflection parameters (top left); group and phase delays of the transmission (top right), TDrs computed with 20 ps rise time Gaussian step (bottom left); eye diagrams for 28 Gbps PrBS signal (bottom right, on top of each other).