Michael Steinberger, Lead Architect, SiSoft
Mike Harwood, Consulting Engineer, HSZ Consulting
Dai Fen, Signal Integrity Engineer, Huawei
Huang Chunxing, Project Leader, Huawei
Steve Hubbins, Senior Member of Technical Staff, Texas Instruments

Serial channels over a lossy cable path can have a much higher bit error rate than channels which use the same pin electronics over a PC board path with approximately the same loss. The problem is that the internal impedance of the cable conductors causes the impulse response of the channel to decay very slowly, resulting in a "long tail" effect.

This paper presents system measurements illustrating the long tail effect, a review of the physics involved, a description of four different methods for compensating for the long tail effect, and a performance analysis of these solutions.