A strategy to optimize Modal Signaling over microstrip lines with spacing variability

Recently, Modal Signaling has emerged as a method for reducing far-end crosstalk in high-speed single-ended signaling channels. Modal Signaling utilizes the orthogonality of fundamental multiconductor transmission line modes to minimize far-end crosstalk over interconnects with inhomogeneous medium, such as microstrip lines on printed circuit boards. A limitation of Modal Signaling is that the channel must be characterized before the appropriate encoder/decoder can be designed. Random variations in the channel characteristics will impact the effectiveness of crosstalk cancellation. This paper explores a variability-aware strategy for designing the Modal Signaling encoder/decoder such that the far-end crosstalk cancellation benefits can be maximized over the manufacturing tolerance range.