Noise Coupling Prediction Inside a Small Shielding Box Based on Phaseless Near-Field Scanning

In this paper, a novel algorithm is proposed to predict the noise coupling between the electromagnetic interference (EMI) source and victim inside the same shielding box. Firstly, the unknown EMI source and victim are represented by equivalent dipoles. The phaseless near-fields radiated from the EMI source and victim under transmitting mode are used to construct the equivalent dipoles. To accurately consider the effect of the shielding box on the equivalent dipoles, the leaked near-fields from the shielding box are used to adjust the moments of the constructed dipoles. Furthermore, the Norton/Thevenin equivalent circuit of the victim is developed, where the excitation current/voltage is obtained by using the reciprocity theorem. Measurement results show the accuracy of the proposed algorithm.

I. Introduction

The miniaturization and high-speed development of modern electronic devices have complicated the electromagnetic environment of printed circuit board (PCB), posing new challenges for electromagnetic interference (EMI) design. Although shielding box can isolate the EMI coupling between inside and outside of the shielding box, the interference within the shield becomes increasingly crucial as components get closer and frequencies higher. Therefore, assessing the radiation emissions inside the shield is an urgent issue to address.