Multimode High-Density Link Design Methodology and Implementation

As higher density of interconnects and packages is demanded, crosstalk noise is becoming more important. Multimode or modal signaling offers the ability to improve wiring density with significantly reduced crosstalk by coding the signals using fundamental modes of propagation only. Past work has demonstrated this on uniform channels. This paper presents a design methodology for designing practical nonuniform high density links using multimode signaling. A channel that consists of printed circuit board (PCB) and package routing, and vertical interconnects is designed to achieve highest density and low crosstalk-induced jitter. Compared to the baseline benchmark channel, the optimized channel demonstrates 4x, 4x, and 2x density improvement of PCB and package vertical and package horizontal routing, respectively, and at the same time achieves a 42% RMS jitter reduction. This new approach significantly improves the ability to design high-density low-crosstalk interconnect subsystems in practical scenarios.