Application of EBG structure to the Reduction of Undesired EM Radiation

The power of undesired electromagnetic radiation from some wireless communication terminals such as a handy-phone and a personal computer tends to raise its level and to extend a frequency range. These terminals are composed of some printed circuit boards PCBs which contains many low-power LSIs, so that the immunity to the electromagnetic wave tends to fragile, and is some possibility of operating incorrectly. Therefore it is important to reduce the undesired EM field radiated from such devices and/or PCB´s. The purpose of this paper is to investigate an absorber housing in the terminal chassis. In general, the absorber made by the normal materials such as a ferrite tile and/or a carbon sponge have some disadvantages regarding its performance and /or its weight.In this paper, the absorption property of the EBG structure is investigated numerically using the FDTD method. In the first half of the paper, the absorption property of a PML (perfect matched layer) slab, which is difficult to realize using the normal material, is calculated. The PML medium may not be realized by the normal materials, but the calculation is to know the upper limit of the absorption efficiency. In the second half, the absorption properties of the EBG structure is calculated and compared with the ferrite slab.