Asymmetric, multi-conductor low-coupling structures for high-speed, high-density digital interconnects

Small inter-line spacings and high switching speeds emphasize the problems of crosstalk and coupling distortion in high-speed, high-density digital interconnects. The use of substrate compensation allows the design of structures in which crosstalk and coupling can be essentially eliminated, even for inter-line spacings of less than one center conductor width. Characteristics of this novel method are presented for both symmetric and asymmetric multiline geometries. Pulse distortion and crosstalk on a four-line, symmetric structure are analyzed, showing how crosstalk and coupling distortion are reduced by substrate compensation. Pulse distortion on symmetric coupled lines is studied, showing that it is possible to choose a substrate combination which significantly reduces coupling and crosstalk for a wide range of conductor configurations