Twisted differential line structure on high-speed printed circuit boards to reduce crosstalk and radiated emission

Abstract

Abstract-Differential signaling has become a popular choice for high-speed digital interconnection schemes on printed circuit boards (PCBs), offering superior immunity to crosstalk and external noise. However, conventional differential lines on PCBs still have unsolved problems, such as crosstalk and radiated emission. When more than two differential pairs run in parallel, a line is coupled to the line adjacent to it because all the lines are parallel in a fixed order. Accordingly, the two lines that constitute a differential pair are subject to the differential-mode crosstalk that cannot be canceled out by virtue of the differential signaling.To overcome this, we propose a twisted differential line (TDL) structure on a high-speed multilayer PCB by using a concept similar to a twisted pair in a cable interconnection. It has been successfully demonstrated by measurement and simulation that the TDL is subject to much lower crosstalk and achieves a 13-dB suppression of radiated emission, even when supporting a 3-Gb/s data rate.

40-Gb/s Package Design Using Wire-Bonded Plastic Ball Grid Array

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Common-mode noise reduction on broadside-coupled delay line

“…Moreover, differential delay lines are gradually becoming more common than single-ended delay line in high-speed routing, PCBs circuits, connectors and interconnect, such as universal-serial-bus (USB), high-definition-multimediainterface (HDMI), etc. Thus, differential delay lines have been widely used to high-speed routing, and some researchers have investigated in previous studies to show their advantages [2][3][4]. In the past, edge-coupled differential delay lines ideally maintained excellent SI and easy for production, delay line research always focused on crosstalk noise, mutual coupling, time-domain reflection (TDR) and time-domain transmission (TDT) waveforms, eye-diagrams and met purpose time delay [5][6][7][8].…”

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