Comparisons of Improvements on Time-doma- in Transmission Waveform and Eye Diagram for Flat Spiral Delay Line between Two Types Guard Traces in High-speed Digital Circuits

This paper investigates the use of the guard traces to improve the Time-Domain Transmission (TDT) waveform and eye diagram for a flat spiral delay line. Two types of guard trace are adopted to implement and analysis in microstrip line and stripline structures. One is Two Grounded Vias type Guard Trace (TGVGT) and the other is Open-Stub type Guard Trace (OSGT). The timedomain analysis results by HSPICE and the associated simple circuit modeling is presented. According to the simulation results, the original TDT crosstalk noises can be reduced by about 80% when using TGVGTs or OSGTs in a stripline structure and by about 60% when using TGVGTs in a microstrip line structure. Additionally, the eye diagrams also can obtain improvement. The crosstalk noise cancelation mechanisms of the flat spiral routing scheme on TGVGTs and OSGTs are investigated by graphic method. In addition, how the degradation for the OSGT inserted into the flat spiral delay line in microstrip structure is clearly investigated. A flat spiral delay line inserted into TGVGTs and OSGTs both can obtain good improvements of the TDT waveform and eye diagram in a stripline structure. Moreover, adding OSGTs to the flat spiral routing scheme is easily accomplished due to the open end of OSGTs. Finally, HSPICE simulation and time-domain measurements of crosstalk noises of TDT waveforms, and eye diagrams are use to validate the proposed structure and analysis. Received 17 April 2011, Accepted 26 May 2011, Scheduled 4 June 2011 * Corresponding author: Guang-Hwa Shiue ([email protected]).