Evaluation of the Effect of Geometrical Configuration on FM‐Band Crosstalk Characteristics between Two Parallel Signal Traces Including Their Divided Ground Patterns on Printed Circuit Boards for Vehicles

SUMMARY Electromagnetic disturbances in vehicle‐mounted FM radios are mainly caused by conducted noise currents flowing through wiring harnesses from printed circuit boards (PCBs) with the slits of ground patterns. To suppress these noise currents from PCBs, we previously performed Finite‐Difference Time‐Domain (FDTD) simulation and measurement using multiple simple two‐layer PCB models in which the ground patterns were divided into two parts with different widths, and revealed that both results agreed well with the fact that crosstalk cannot always be reduced by increasing the width of divided ground patters, but had the smallest values (dipping point) at a specific spacing between the divided ground patterns. In order to clarify the above result, we calculated crosstalk using a formula developed from a simplified equivalent circuit model consisting of inductances, derived from their geometrical mean distances (GMDs) from the traces and ground patterns, and found that the calculation results also had dipping point. However, the specific spacing and crosstalk values were different from the simulations and measurements. In the present study, to improve calculation accuracy, we considered nonuniformity of the current distribution in the ground patterns instead of a uniform current distribution, and obtained crosstalk evaluation results which agreed better with simulations and measurements.