Measurement and simulation of crosstalk reduction by 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 paper evaluates coupled surface microstrip transmission lines with periodical loading and coupling. The situation may represent stray coupling and loading of digital buses due to connector pins, plated through holes at connector slots, and stubs as well as the input capacitance of active devices. This paper shows 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. The reduction of far-end crosstalk is verified by measurements, and the good agreement between the simulated and measured data is shown. On the other hand, discrete loading does not significantly reduce near-end crosstalk, but will introduce additional ringing in the time domain