Mixed-signal equalization architectures for printed circuit board channels

This paper develops mixed-signal equalization solutions for gigabit communications in printed circuit boards (PCBs). The PCB channel, composed by vias and interconnects, distorts, and produces signal reflections that deteriorate quality of high-speed data transmission. Analog signal processing architectures are necessary to combat the inter-symbol interference effects introduced by the channel since high-speed analog-to-digital conversion is a very expensive solution. A novel system implementation and circuit-level architecture that performs mixed-signal feedforward (FF) and feedback (FB) equalization in the transmit end is introduced. System level simulations show how this combined FF-FB transmit equalizer outperforms the conventional pre-emphasis structures presented in previous works, with a reasonable compromise in circuit area. In addition, practical constraints like the maximum output signal, the filter coefficients spread, and the sensitivity of the solution with respect to components variation are presented, demonstrating the robustness of the proposed architecture.