DesignCon 2002

Figure 3: Blade server simulated channel.
Post-layout modeling was achieved by extracting the Allegro CAD layout for each of the
three PWBs with Ansoft Links and then importing them into Ansoft’s SIwave.
SIwave was then setup to provide a channel model from DC to 20GHz utilizing the 24
layer stack-up for each board. The full-wave, package field solver models each PWB
using a two-dimensional Finite Element Method for all extracted plane geometries and
cavities. This is combined with a Method of Moments solution for each signal trace that
results in a very accurate touchstone or Full Wave Spice file that is used to determine the
system response of the BladeServer. To ensure passive and causal transmission line
responses, the full-wave, package field solver uses a Djordjevic [4] frequency-dependent
model for the dielectrics contained within the PWB.
Finally, time-domain simulations were run for all of the cases so that a prediction of the
system performance at 10 Gb/s could be obtained with and without equalization.
Statistical analysis methods were employed to assist in determining the sensitivity to
transmitter random jitter (TXRJ) and duty-cycle distortion (DCD). Feed forward
equalization and decision feedback equalization algorithms inherent to the circuit
simulator tool were utilized to determine tap weights and eye openings at the pad of the
silicon receiver.
Statistical Analysis – VerifEye
VerifEye is a new, statistical tool for generating contour eye diagrams and bathtub curves
for a channel. By combining the statistics of the bit stream with the variation in