Modeling Electromagnetic Emissions From Printed Circuit Boards in Closed Environments Using Equivalent Dipoles

In this paper, a method for representing electromagnetic emissions from a printed circuit board (PCB) using an equivalent dipole model deduced from near-field scanning is proposed. The basic idea is to replace the PCB with a set of infinitesimal dipoles that generate the same radiated fields. Parameters of the equivalent dipoles are determined by directly fitting to the measured magnetic near fields. In closed-environment simulations, the equivalent method is extended to a dipole-dielectric conducting plane model to account for the interactions between the PCB and enclosure by including the basic physical features of the PCB. The electromagnetic emissions can then be predicted by solving the equivalent model with numerical methods, thereby, significantly reducing the simulation time and storage costs. A basic test board and a more complex practical telemetry PCB are modeled in different configurations and compared with measurements and full-field simulations, confirming the validity and efficiency of the model.

I. Introduction

For some design engineers, issues of electromagnetic compatibility (EMC) are only marginally considered. But the significant increase in clock frequency of electronic circuits to several gigahertz means that printed circuit boards (PCBs) have become efficient radiators of electromagnetic energy. Also, high-density packaging is widely applied to PCB design, leading to more electromagnetic interference problems between PCBs, particularly within enclosures. Hence, the consideration of EMC during the design phase of high-speed systems is becoming critically important. However, direct simulations, modeling PCBs with all their complexity in full-field solvers, is not feasible for EMC studies. This is because of the unrealistic demands on computational resources, unknown out of bound frequency characteristics, and commercial confidentiality. Therefore, it is useful to provide efficient simplified equivalent models to accurately predict the radiated emissions without reference to the exact details of the PCB. The equivalence principle has been successfully used to address practical EMC problems at the PCB level [1], [2].