A Serpentine Guard Trace to Reduce the Far-End Crosstalk Voltage and the Crosstalk Induced Timing Jitter of Parallel Microstrip Lines

A serpentine guard trace is proposed to reduce the peak far-end crosstalk voltage and the crosstalk induced timing jitter of parallel microstrip lines on printed circuit boards. The vertical sections of the serpentine guard increase the mutual capacitance without much changing the mutual inductance between the aggressor and victim lines. This reduces the difference between the capacitive and inductive couplings and hence the far-end crosstalk. Comparison with the no guard, the conventional guard, and the via-stitch guard shows that the serpentine guard gives the smallest values in both the peak far-end crosstalk voltage and the timing jitter. The time domain reflectometer (TDR) measurement shows that the peak far-end crosstalk voltage of serpentine guard is reduced to 44% of that of no guard. The eye diagram measurement of pseudo random binary sequence (PRBS) data shows that the timing jitter is also reduced to 40% of that of no guard.