MEASUREMENT AND SIMULATION OF CROSSTALK REDUCTION BY DISCRETE DISCONTINUITIES ALONG COUPLED PCB TRACES

Crosstalk among interconnects and printed-circuit board (PCB) traces i s a major limiting factor of signal quality in high-speed digital and communication equipment. The paper evaluates coupled surface microstri p transmission lines with periodical loading and coupling. The situati on may represent stray coupling and loading of digital buses due to co nnector pins, plated through holes at connector slots, and stubs as we ll as the input capacitance of active devices. This paper shows that d iscrete periodical coupling along coupled surface microstrip transmiss ion lines may be used to reduce far-end crosstalk. An expression is gi ven to calculate the discrete coupling capacitance to achieve optimum far-end crosstalk reduction. The reduction of far-end crosstalk is ver ified by measurements, and the good agreement between the simulated an d measured data is shown. On the other hand, discrete loading does not significantly reduce near-end crosstalk, but will introduce additiona l ringing in the time domain.