Suppression Effect of Emission from Printed Circuit Board Using Conducting Plate

For emission from a printed circuit board (PCB) by the common-mode current the suppression method based on the image theory by placing a conducting plate under the PCB is presented. In order to evaluate the suppression effect by this method the radiation power from the PCB is calculated by using FDTD method. The numerical results show that placing the conducting plate near the ground side of the PCB suppresses effectively the emission by the common-mode current. Especially, using the conducting plate bent the sides, it is possible to suppress the emission by the small conducting plate. Moreover, the method by bending the edges of the PCB is presented and is showed that large suppression effect is obtained using this method. Further, the experimental results of a maximum electric field intensity show the validity of the numerical results.