Analysis and Reduction of Coupling Noise in Coupled Striplines With Inserted Guard Trace With Different Trace Spacings

This paper investigates how crosstalk coupling noise is generated in coupled striplines with inserted guard traces with different trace spacings. Design guidelines for reducing noise and the implemented noise reduction scheme, involving an additional grounding via on the guard trace, are proposed. A graphical method that is based on wave tracing is presented to illustrate the generation of crosstalk noise on the guard trace and the victim line. The results of simulations in the time and frequency domains, performed using HSPICE and the 3-D full-wave simulator high frequency structure simulator, are presented to elucidate the noise coupling. The 3-D full-wave simulator, computer simulation technology, is utilized to validate the time-domain simulation results. Approximate formulas for the amplitude of the induced crosstalk noise are presented. The magnitude of the time-domain crosstalk noise on the victim line is reduced by more than 70% using the reduction scheme with the additional grounding via. Moreover, in the frequency domain, the reduction of the magnitude of the first resonant crosstalk peak at approximately 1 GHz is over 25 and 35 dB for crosstalk noise at the near end and the far end, respectively. The maximum reduction of the measured common-mode current that is generated by the different trace spacings in the attached I/O cable exceeds 35 dB at the first resonant frequency. Finally, the frequency-domain measurements of crosstalk noise support the proposed analyses.