In 1990, Railton and McGeehan [118] presented the first FDTD model for thin sheets of conducting or dielectric material. In 1991, Tirkas and Demarest [119] presented an FDTD model for thin dielectric sheets that treated not only the tangential component of the electric field at the air/sheet interface, but also treated the normal component of the field in the sheet. Independently, in 1992 Maloney and Smith [120] presented a somewhat similar formulation, but also allowed for the modeling of thin conducting sheets. Luebbers and Kunz [121] and Boonzaaier and Pistorius [122] have also presented methods for treating thin material sheets, all of which treat only the tangential component of the electric field at the thin sheet/air interface. Finally, a comparison of the FDTD methods for modeling thin dielectric and conducting sheets was given by Maloney and Smith [123].