Energy Efficient Transfer of Microwave Power to Thin Lossy Dielectrics

Microwaves beamed on a dielectric are partly reflected on, and partly transmitted to the dielectric. If the dielectric has a finite thickness the microwaves propagating through the dielectric consists of forward as well as backward moving waves. The reflected wave on the dielectric means loss of energy, the backward components of the wave in the thin dielectric are causing strong oscillatory behavior of absorption in the dielectric which can lead to hot spots. For thin dielectrics, in general, the power penetration depth cannot be used to calculate the power absorption in the dielectric. In this paper it will be shown that with oblique incidence, in a special case, all power irradiated to a thin dielectric can be absorbed and that for this situation the power penetration depth can be used to calculate the power absorption because backwards waves are not present in the dielectric. It will be shown that this occurs also if a suitable medium is situated around the dielectric to be heated. Also in this case all power is absorbed by the dielectric and the power absorption can be described by the power penetration depth. Both possibilities mean a very efficient energy transfer to the dielectric. For thick dielectrics all energy beamed to the dielectric is absorbed.