Research On Cavity Shielding Effectiveness Using Hybrid Fdtd Method

With the rapid progress and development of scientific technology , electromagnetic interference become more and more important in the complex electromagnetic environment. For the electromagnetic interference, it is not only reduced the performance of electronic equipment, but also interfered strongly or even seriously damaged electronic equipments and electric system working under nature conditions. In order to avoid the electromagnetic energy coupling, generally speaking, metallic enclosures wrapped the sensitive equipment to cut off the path of electromagnetic interference and shield the complex interference signal from outside. However, the metallic enclosures can not completely cut off the interference signal because in most applications, slots, holes, and even a window aperture have to be created on the walls of the enclosure for signal wiring, power supply, and heat dispersion. These slots, unfortunately, create electromagnetic energy coupling paths that allow outside electromagnetic waves to propagate into the enclosure; they thus degrade the shielding effectiveness (SE). As a result, many theoretical and experimental studies have been carried out to model, design, and optimize an effective metallic enclosure for different electronic systems.The finite-difference time-domain (FDTD) method has been proven to be very effective for computing the interactions of electromagnetic fields with various conductive composites. As a time-domain technique, FDTD directly computes the wideband responses and thus can provide results over a wide frequency range through a single simulation, including the shielding effectives. In this paper, we researched the thin slot subcellular models and calculated the cavity shielding effectiveness using it. Then we compared the numerical results and the measured results and verified the validity and accuracy of the algorithm. The thin slot subcellular models is not only reduced the computational complexity, but also decreased the computing time and memory.For the shielding effectiveness of metallic enclosures, this paper proposed a new definition, which is called the cavity average shielding effectiveness. New definition can better description the change of shielding effectiveness for the whole metallic cavity and it is more universal and general.This paper carried out to model realistic EMC shielding structures that had both thin slots and holes and calculated the cavity shielding effectiveness in different pulse parameter, different aperture array of cavity surface, different cavity sizes and different polarization angle of incident pulses etc. using hybrid FDTD. The results give a theoretical guidance for the design of high-performance shielded cavity.