S-Parameter-to-Impedance Conversion for High-Speed PCBs and Via-Breakout Optimization

Abstract

This study combines mixed-mode frequency-domain analysis over 0.005–4.000 GHz with a separate 4 Gb/s QuickEye comparison of conventional and near-via P/N compensation layouts. The four-port SIwave export shows the lowest sampled differential reflection at 1.134899 GHz and a selected local minimum at 2.950808 GHz. At the latter frequency, Sdd11=−0.006669+j0.004975, giving a differential input impedance of 98.670+j0.982Ω with a 100 Ω reference. In the paired layout simulations, differential return loss improves by 3.26 dB near 3 GHz, and Sdd21 changes from −1.01 to −0.99 dB at the cursor. Insertion loss does not improve consistently across 0–4 GHz. At the saved 250 ps unit interval (4 Gb/s), QuickEye eye width increases from 212.4549 to 219.0924 ps, and RMS jitter decreases from 6.2575 to 5.1513 ps. The 0–4 GHz sweep reaches the 4 GHz Nyquist frequency of PCIe 3.0, but the 4 Gb/s time-domain comparison remains below the 8.0 GT/s PCIe 3.0 line rate and does not assess compliance.