A hybrid stack-up of printed circuit board for high-speed networking systems

Printed circuit board (PCB) design is getting critical as data rate approaching 25 Gbps (Gigabit per second) and beyond in networking systems. Channel loss, noise coupling and discontinuities are limiting the performance of high-speed channels. Equalization techniques including linear, feed forward and decision feedback are widely used in high-speed SerDes channels to compensate the channel losses. But these are still not sufficient for some extra long channels, and low loss PCB dielectric materials have to be used finally. The consequence is the cost of the networking system soaring significantly. In this paper, a hybrid stack-up is proposed for PCBs used in networking systems. Electrical performance of the hybrid stack-up is investigated in both frequency-domain and time-domain, and a positive conclusion for the hybrid stack-up is reached based on its cost and electrical performances.