Promoting Axial, Uniformity in Radio Frequency Heating of a Lossy Material in a Waveguide by Introduction Of an Insulating Gap

It is shown that the introduction of an insulating gap in a parallel plate waveguide filled with lossy material produces an axial electric field in addition to the transverse electric field already present. When the waveguide is terminated in an open or short circuit, then the standing wave patterns created by the transverse and axial electric fields have interleafing nodes, so that the node of one standing wave pattern is coincident with the antinode of the other. This phenomenon leads to radio frequency heating of the lossy material that is much more uniform in the axial direction than would be the case if the lossy material were to fill the entire space in the waveguide. The technique is applied to show how to heat oil sand deposits fairly uniformly with radio frequencies to aid in the recovery of the resource. It is equally applicable in other areas, for example the radio frequency heating of industrial materials, food stuffs, and biological tissue.