Two techniques for intra-pair length matching of differential routing are proposed: Asymmetrical Dual Bend(ADB) and Hybrid U-Turn(HUT), in order to reduce the differential mode to common mode conversion in system. These layout techniques help in achieving lower EMI without impacting SI performance and with insignificant effect on PCB cost.
1. Four types of Asymmetric Dual Bend(ADB) designs are evaluated in this presentation by simulating the EMI and SI performance. The results illustrate that the asymmetric dual bend scheme can provide 10+ dB improvement for Scd21 in stripline layout and nearly 5dB improvement for microstrip layout, while no impact on SddSeveral PCB coupons were also made, and the results match quite well between simulation and measurement.
2. Hybrid U-Turn(HUT) is proposed in this presentation for intra-pair length matching as well as inter-pair skew simultaneously by introducing two different kinds of corners. The simulation results show nearly 10dB improvement in Scd21 and PCB coupon measurement also verify the performance.