SUMMARYIn this paper, a highly accurate equivalent circuit is constructed that can calculate the transmission characteristics of the vias connecting the layers in multilayered printed circuit boards. Various factors of the vias affecting the transmission characteristics are discussed. The present equivalent circuit is based on the physical structure and the equivalent circuit parameters are determined by an optimization method. The equivalent circuit is applied to the vias in printed circuit boards with more than 10 layers. The results of evaluation of the transmission characteristics in the gigahertz range are verified by the FDTD method and by measurement so as to verify their validity. Further, by using the present equivalent circuit, the effects of various factors of the vias on the transmission characteristics are studied. It is demonstrated that the time needed for study by the equivalent circuit is less than that needed for numerical analysis.

This study was performed to design a practical printed wiring board in which the EMI from electronic equipments can be controlled. When the target board is connected to the cable under EMI test conditions, it is shown that the common mode current which is the main cause of radiation occurs with mismatching of an unbalanced degree between the board wiring and the cable. Furthermore, we use CMRR (Common Mode Rejection Ratio) as an index for evaluating the unbalanced degree, and propose the CMRR measurement method for board wiring based on a Faraday Cage and a network analyzer. By designing the board adjusted to the degree of unbalance of the connecting cable, it is expected that the common mode current will be suppressed and component parts for control of EMI can be reduced.