Coupling reduction in enclosures and cavities using electromagnetic band gap structures

The physical mechanism behind electromagnetic interference (EMI) is the coupling of energy between different primary and secondary sources of radiation and components within the package or chassis. This coupling can be either through conduction or radiation. However, regardless of the coupling mechanism, surface currents are needed to support the electromagnetic fields that eventually cause radiation, which in turn, constitute the EMI in the victim component. Minimizing these surface currents is considered a fundamental and critical step in minimizing EMI. In this work, we address novel strategies to confine surface currents. Unlike the traditional use of lossy materials and absorbers, which can be costly and can suffer from considerable disadvantages including mechanical and thermal reliability leading to limited life time, we consider the use of electromagnetic band gap (EBG) structures. These structures are inherently suited for surface current suppression. Their design is straightforward, and they are inexpensive to implement and do not suffer from the limitation of the previous methods used for the type of EMI suppression previously described. The effectiveness of the EBG as an EMI suppresser will be demonstrated using numerical simulations and measurements.