Using rectangular-patches (RPs) to reduce far-end crosstalk noise and improve eye-diagrams on microstrip helix delay line

Delay lines are widely employed in high-speed circuit for delay time synchronization and timing skew minimization, popular schemes are serpentine and spiral routing. In order to reduce the manufacture cost and routing area, spacing between adjacent unit lines should be smaller, but it increases in electromagnetic coupling and crosstalk from adjacent lines. In conventional serpentine and spiral delay lines, near-end crosstalk (NEXT) is a main noise that accumulates at the receiving end and results in waveform degradation of time-domain transmission (TDT). Although there are many strategies for crosstalk noise reduction, yet the crosstalk noise like NEXT always exists and may affect system-level timing and cause error switching of logic gates. This paper proposes two novel structures; one is helix delay line, and the other is helix delay line with rectangular-patches (RPs). Compared with conventional serpentine and spiral delay lines, the far-end crosstalk (FEXT) is a dominant noise that accumulates at the receiving end. Simulation results show that FEXT noise in helix delay line with RPs structure can dramatically decrease 77.6%, eye-opening and eye-jitter can improve 28% and 33.4% compared with helix delay line without RPs.