Measurement and computer simulation of discrete discontinuities along coupled PCB traces

Crosstalk among interconnects and printed circuit board (PCB) traces is a major limiting factor of signal quality in high-speed digital and communication equipment. The authors evaluate coupled surface microstrip transmission lines with periodical loading and coupling. The situation represents stray coupling and loading of digital buses due to connector pins and plated through holes at connector slots. It is shown that discrete periodical coupling along coupled surface microstrip transmission lines may be used to reduce far-end crosstalk. An expression is given to calculate the discrete coupling capacitance to achieve optimum far-end crosstalk-reduction. Discrete loading does not significantly reduce near-end crosstalk, but will introduce additional ringing in the time domain