Using Rectangular-shape Resonators to Improve the Far-end Crosstalk of the Coupled Microstrip Lines

Modern electronic products must have high-speed, high-density layout, small size, faster rising time and lower voltages supply. With such design, signal integrity (SI) becomes a very important factor because sensitive equipment is afiected by electromagnetic interference (EMI) and noise interference. Crosstalk is a major factor in SI from printed circuit boards (PCBs). Crosstalk noise is usually represented in terms of near-end crosstalk (NEXT) and far- end crosstalk (FEXT). In order to cost concerns, microstrip line is widely used for PCBs because it's easy to manufacture. In microstrip line structure, FEXT is induced by the difierence between the capacitive coupling ratio (Cm=CT) and inductive coupling ratio (Lm=LS). In earlier research, however, many researchers had proposed solutions that are guard trace which are used to reduce NEXT and FEXT. Since a large number of shorting-via degrades the SI and reduces the ∞exibility of the circuit routing. Another technique to reduce the FEXT noise is serpentine guard trace, but this kind of guard trace requires to be terminated with matched resistances at both ends of guard trace. In this paper, we propose a method to reduce the far-end crosstalk by using rectangular-shape resonators (RSR) structure. In which, the shorting-via and resistance are not necessary to be used for improving the FEXT. The frequency-domain simulation of HFSS shows that the S41 of RSR structure is decreased more than 7dB compared to the 3-W rule. The time- domain simulation of ADS shows that the peak of far-end crosstalk voltage of RSR structure is improved to 54% compared to the 3-W rule.