Improvements of time-domain transmission waveform and eye diagram of serpentine delay line using guard trace stubs in stripline structure

Abstract

The utilization of guard traces with two ground vias at both ends to improve the eye opening and jitter for serpentine delay lines has been investigated. However, it is not easy to accomplish using normal manufacturing technology nowadays because the position of the pad of grounded via is surrounded by serpentine trace. This is especially true in normal manufacturing technology, in which size of the via pad is larger. Therefore, this study proposes crosstalk noise reduction of the time-domain transmission (TDT) waveform and eye diagram of the serpentine delay line by guard trace stubs, i.e. the guard trace of one end is grounded via and the other is open-end, with stripline structure. The crosstalk reduced efficiency for using guard trace stubs is the same as when using guard traces on the time domain of the serpentine delay line. This is because, the open-end leads to the noise cancellation mechanism of the guard trace stub. Based on HSPICE simulation, it demonstrates that the utilization of the guard trace stubs can reduce the original TDT crosstalk level by more than 50%, thereby greatly improving the eye opening and jitter. Finally, this study also performs time-domain measurement to validate the proposed analyses.