In this paper

the moment method

which is capable of being used to solve the problem of combination of a waveguide with a stratified dielectric loaded rectangular cavity

is used to calculate the distribution of microwave fields in the load of a stratified-Ioaded box-type microwave heater

excited by a waveguide

the fields and the input voltage standing wave ratio on the surface of the excited aperture. Optimization of some parameters such as the location and the orientation of the excited aperture is performed in accordance with the requirements of improving the heating uniformity for the load.