Comparison between flat spiral and serpentine differential delay lines on TDR and TDT

In contrast to the commonly employed single delay lines, differential delay lines may alleviate the occurrence of crosstalk and improve the signal integrity. This work investigates the TDR and TDT for differential delay lines with serpentine and flat spiral layout design. The TDR/TDT waveforms and TDT eye diagrams are simulated and presented to investigate the improvement in the signal integrity and noise margin. Signal waveforms and eye diagrams of four basic routing schemes are obtained by the detailed HSPICE simulation. It is found that the combination of differential signaling and flat spiral layout can exhibit the best delay line performance.