Abstract: This invention provides a microwave oven that is supplied with microwave energy through upper and lower feed openings in a side wall of the cavity. A wave guide is provided to feed those openings and is dimensioned to provide a resonance condition in the wave guide and a selected quality factor (Q-value) which is high in comparison with the Q-value of the oven cavity.

Abstract: In certain types of microwave ovens, e.g. ovens of the single-wall type, the manufacturing of the oven cavity (10) involves the forming of at least one groove-shaped recess (16) in at least one of the cavity walls (14). In order to substantially eliminate the disturbing effect of this recess (16) on the microwave field pattern in the oven cavity (10), a reflecting element in the shape of an elongated strip (18) of conductive material is provided in a position at the entrance opening of the recess (16), as seen from the oven cavity (10). The conductive strip (18) is preferably covered by dielectric material, e.g. in the shape of a dielectric plate (20) that also serves as support for the strip (18), and this strip (18) is so dimensioned and disposed at the opening of the recess (16) that it substantially reflects all incident microwave radiation coming from the oven cavity (10) at the operational frequency of the microwave oven.

Abstract: An arrangement for feeding microwave energy from a microwave source (14) to the oven cavity (10) of a microwave oven comprises an elongated groove-shaped recess (16) in one of the conductive cavity walls (17), into which recess (16) microwave energy is fed at a centrally located feeding point (15). At its open side the recess (16) is covered by a rotatable conductive plate (22) arranged very close to the cavity wall (17) so that the recess (16) together with the plate (22) will form a waveguide-like structure. The plate (22) is shaped so that during its rotation time-varying feeding passages between the recess (16) and the oven cavity (10) are formed at both opposite ends of the recess, the passages allowing the transfer of microwave energy from the recess (16) to the cavity (10). These measures result in a very simple and space-saving arrangement of the "dual feed" type.

Abstract: A microwave oven is shown which has a defrosting mode the length of which is determined solely by the humidity in the air in the oven provided by moisture from a frozen article, particularly frozen food, being defrosted in the oven.

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).

Abstract: A microwave heating applicator usable in preformed holes in mansonry and the like for heating and dehumidifying areas around the holes is formed from a length of coaxial transmission line. Radiating elements are formed in the outer conductor of the coaxial line for providing an asymmetrical radiation pattern. The radiating elements are provided by forming circumferential axial discontinuities in the outer conductor, each discontinunity having a pair of non-parallel cut edges formed in the outer conductor encircling the line, leaving an asymmetrical open area extending axially between the cut edges. One of the cut edges may describe a plane perpendicular to the coaxial line's z axis while the other cut edge describes a plane which is not perpendicular to the coaxial line z axis. The radiating elements may be provided at intervals along the coaxial line.

Abstract: A method and apparatus for the treatment of protein containing foodstuffs wherein the foodstuffs are pumped in a microwave transparent tube through an applicator for exposure to microwave TM.sub.021 energy. The foodstuffs may be in paste form. If the foodstuffs are eggs, the yolks and egg whites are pumped through concentric tubes before combination thereof in the applicator.