Analysis of electromagnetic coupling between microstrip line and ground slot on a printed circuit board

By advance of miniaturization of electronic devices, grounds of a printed circuit board are tend to be small and complicated and may have some defects, such as connectors or clearance halls of vias. In this paper, we analyzed the electromagnetic coupling between a microstrip line and a slot in a ground on a PCB using the multi-conductor transmission lines method to examine the signal integrity of the line. To calculate by using the MTL method, per-unit-length parameters, such as the self and mutual capacitances and inductances, of a microstrip line and a ground slot were calculated using the spectral domain approach. We calculated the coupling voltages in the ground slot excited by the microstrip line using the MTL method and the FDTD method and showed the validity of the proposed method by comparing the results of both methods when the microstrip line and the slot were located closely. Finally, we calculated the coupling voltages in the slot versus the space between a microstrip line and slot and showed that the coupling voltage was reduced as the thickness of the PCB decreased. And also, we showed that the accuracy of the MTL method is improved by applying a radiation loss from the ground slot.