Multi-gigabit communications present many challenges to cable manufacturers. How can bandwidths higher than 10Gbps required by new standards such as HDMI and DisplayPort be achieved over low cost cables? What are the core technical problems with achieving these high data rates and what technologies can be used to address them? How can manufacturers achieve solutions which are less dependent on copper pricing? How can reliability issues be resolved without the need to use thicker cables? Cable manufacturing techniques have evolved to try to meet the challenge, but semiconductor solutions are emerging as promising alternatives and can be expected to play a significant role in solving these issues.
This article explains the physical problems faced by cable manufacturers, in particular differential skew and limited bandwidth. The origins and implications for both problems are explained using eye diagrams. The article presents a silicon solution for these problems, discussing the challenges associated with circuits which automatically de-skew and the requirement for equalization to address the limited bandwidth problem. Data recovery is shown to be dramatically improved when adaptive de-skew and equalization is applied.
Cost-effective silicon embedded in a cable bulk-head, combined with low-cost manufacturing techniques (high AWG cables, etc), provide cable manufacturers with a competitive solution in terms of performance and cost.
Cable Manufacturers need to embrace semiconductor technology. Embedded silicon can answer the commercial and technical issues facing the industry today.
The Cable Problem
The main challenge for cable manufacturers is to solve the issue of propagation delay difference and high frequency suppression problems associated with the eternal need for increased data-rates. Propagation delay difference varies with cable length and dielectric constant and causes increased common-mode noise (cross-talk, EMI) and reduced transmission margin. High frequency suppression is a function of conductive loss (skin-effect and shield current) and causes increased rise times and reduced amplitude on the transmitted signal.
To combat these effects, manufacturers need to optimize the selection of cable type (moving away from STP to TWINAX or SCTC), dielectric performance (use mechanical foaming) and conductive material (use solid and not stranded material and move to low AWGs). These solutions are expensive and bring other challenges to the cable (bulkiness, weight, rigidness, solder-cracking in connector, etc). An alternative approach is to consider cost-effective embedded semiconductor solutions such as RedMere's MagnifEye Repeater, MagnifEye Switch and Cable MagnifEye solutions which solve these intra-pair skew and high frequency attenuation problems for different cable applications, allowing cable manufacturers to work with thin low-cost cables such as 36 AWG.
