Crosstalk and Common Mode Noise Reductions in High-Speed Coupled Transmission Lines

Abstract

Today, the progress of modern technology has led to an increasing tendency toward higher speed, faster rising time, high density routing, and low-voltage operation; these trends will increase the difficulty of trace layout and chip placement, and it should make serious considerations of electromagnetic compatibility and common mode noise. In addition, signal integrity (SI) becomes more and more important design factors in high-speed board (PCB). In order to overcome these problems, differential signaling has been used since it has lower electromagnetic interference generation and higher common mode noise immunity. Because differential transmission lines offer a virtual ground in the middle between positive and negative lines, the differential signaling gradually becomes a common routing method and it is commonly used to high speed inter-connector interface, such as the universalserial- bus, digital-visual-interface, display-port, highdefinition-multimedia-interface, and so on. With such designs, the signal integrity (SI) problem in a poor highspeed printed circuit boards (PCBs) layout is affected by noise. Among these factors, crosstalk and common mode noise are major sources of noise to interfere with signal integrity (SI), and crosstalk problem and common mode noise are getting worse because layout density is increasing between connections of chips.