Confined Modes Between a Lossy Slab Load and a Metal Plane as Determined by a Waveguide Trough Model

The particular mode types which can propagate in the region underneath a large thick food item in for example a microwave oven are investigated by a model using the geometry of a rectangular wave guide trough. The waves are trapped surface waves and may have inefficiently small losses to the load if there is no additional dielectric layer such as a shelf Too high losses, resulting in absorption of most of the energy in the outer parts of the load may, however, occur in slabs having dielectric properties corresponding to those of large frozen food items.