Scrambling data signals for EMC compliance

This paper discusses the benefits of scrambling high-speed data signals for reducing the electromagnetic radiation from the electrical interconnects that propagate these signals. It is shown how maximum length sequences, generated through the use of tapped shift register scrambling structures, can significantly mitigate the electromagnetic interference from data signals that are inherently periodic in the time-domain. Specifically, it is shown how a 7-bit scrambler enabled the EMC margin of a system to be increased from -3.5dB without the scrambler, to +5.5dB with the scrambler, resulting in a +9dB improvement in the EMC performance of the system.