Multi-resonant microwave oven having an improved microwave distribution

Abstract

A microwave oven comprises an oven cavity (10) bounded by conductive walls (11-16) and a microwave source (17-19) situated such that microwave energy is fed from above into the oven cavity (10). A bottom plate (20) of a dielectric material is situated above the conductive bottom wall (16), on which plate (20) food to be heated (21) is placed. Two conductive ridges (24, 25) project from the conductive bottom wall (16), which ridges (24, 25) are situated adjacent and in parallel to the respective shorter conductive side walls (12, 14). The dielectric bottom plate (20) is placed and dimensioned such that a trapped TM resonant mode is generated in the space between the upper surface of the bottom plate (20) and the conductive bottom wall (16). This trapped TM resonant mode is excited via the bottom plate (20) and the ridges (24, 25) by the microwave field above the bottom plate (20), microwave energy from the TM resonant mode within and below the bottom plate (20) will 'leak' into the food (21) owing to its higher dielectric constant, whereby the food (21) will be subjected to an appreciable heating from below.