4 Cross Talk Mitigation

PCIe Gen5 cross talk needs to be mitigated, meaning there is a total channel loss that needs to be considered. We must allow at least 4 to 5 dB increased signal strength versus total system loss. This mitigation can be achieved by reducing differential signal loss insertion loss (SDD21) or improving cross talk. This 4 to 5 dB of signal strength improves the signal to noise ratio and thus improves the targeted BER (1E-12). To reduce the effect of cross-talk, maximize pair-to pair spacing, ground stitching, and the optimization of via anti-pads – more details about the listed topics are discussed in later paragraphs. Typically, it is advised to use closely coupled strip line to reduce the effect of cross-talk . However, vias and anti-pads need to be designed carefully. The DS320PR1601 TI EVM is designed using a co-planar GND reference waveguide, which reduces the effects of cross-talk.