Measurement and simulation correlation of backplane serdes channel

Abstract

Serial data link has been widely used in telecom industry. The ability to accurately predict serdes channel insertion loss and return loss plays a critical role in prediction of serdes link performance. In a recent project we designed some test cards with the objective to characterize backplane serdes channel and conduct measurement to simulation correlation. The first part of the study is to try to correlate differential insertion loss (phase and amplitude) of 2D transmission lines between measurement and simulation. A wide band W element model extracted with Simbeor is verified and used in subsequent simulation. In the second part of the study, a full backplane serdes channel consists of daughter cards, backplane, connectors, vias, SMA launches is simulated and compared with TDR measurement. Each element is represented by a S parameter black box and cascaded together with verified W element model for PCB trace. Care must be taken when dealing with cascaded S parameter boxes in time domain simulation. Reasonable agreement is achieved on TDR/TDT signature, differential insertion loss and return loss. The final verification is an eye diagram simulation using real serdes device silicon model and compare eye diagram simulation based on measured s4p and that from S parameter model. In this paper, we presented the methodology and flow that was adopted in this study.