Abstract
It is well known that electromagnetic disturbances in vehicle-mounted radios are mainly caused by conducted noise currents flowing through wiring-harnesses from vehicle-mounted printed circuit boards (PCBs) with common slitting ground patterns. To suppress these kinds of noise currents from PCBs, we previously measured them for simple two-layer PCBs with two parallel signal traces and slitting or non-slitting ground patterns. The results revealed that making slits with open ends on the ground patterns in parallel with the traces can reduce the conducted noise currents. To verify the contributor factor, we then investigated the reduction characteristics of the FM-band cross-talk noise levels between two parallel signal traces on four simple PCB models using FDTD simulation. Each PCB model had different slitting ground patterns in which the slits were parallel to the traces but had the same planar dimensions. Another two simple PCB models in which the ground patterns were divided into two parts parallel to the traces were also investigated. As a result, we found that the contributory factor for the FM-band cross-talk reduction is the reduction of mutual inductance between the two parallel traces. Moreover, it is also interesting to note that the noise currents from PCBs can rather be suppressed even if the size of the return ground is small. In this study, to further confirm this finding, we simulated the characteristics of cross-talk reduction for additional six simple PCB models which have different ground patterns sizes and each ground pattern is divided into two parts parallel to the traces. The results also confirmed the interesting phenomenon of cross-talk reduction characteristics.
