A microwave heating apparatus has a heating chamber in which an object is to be heated both dielectrically by microwave and by radiant energy. A microwave generator for generating microwaves is disposed above the heating chamber, and a radiant energy heater is located within the heating chamber. A rectangular wave guide extends between the generator and an opening in the chamber for guiding the microwaves generated by the generator into the heating chamber from above, the wave guide being bent generally in the shape of the letter Z and the portion of the wave guide other than the portion adjacent the opening into said heating chamber being spaced from the walls of the heating chamber. Thermal insulation is provided between the chamber and the portion of the wave guide spaced from the walls of the chamber.

A system for improving the uniformity of distribution of microwave power in a microwave cavity, includes a magnetron, a wave guide extending between the magnetron and the interior of the microwave cavity for coupling microwave power into the microwave cavity and drive means operative coupled to the wave guide to vary the direction in which microwave power is introduced into the cavity.

A microwave oven, which has a circular polarized wave stirrer for uniformly heating food, is disclosed. The microwave oven includes a magnetron generating electromagnetic waves, a waveguide guiding the electromagnetic waves generated from the magnetron to a cavity, and a stirrer formed to an outlet of the waveguide, receiving electromagnetic waves from the magnetron, and generating two polarized waves having different electric field directions and phases.

The present invention relates to an apparatus for heating a sample, such as chemical reaction mixtures, whose dielectric properties varies during the heating process. In particular, the present invention relates to a microwave heating apparatus comprising a microwave generator, a waveguide for guiding the generated microwaves to an applicator, and a deflector formed by a closed loop defining a plane, said deflector having an inherent resonance frequency and a thickness in a direction normal to said plane, the deflector being rotatable around an axis being at least substantially parallel to said plane, the deflector being positioned in the waveguide so as to form a resonant cavity with the sample and the waveguide applicator. The resonance conditions of the resonant cavity and the coupling factor of radiation from the waveguide to the cavity are easily adjustable by rotation of the deflector. The resonance conditions and the coupling factor can be adjusted in response to the dielectric properties of the sample in order to optimise the amount of absorbed power and thereby obtain control of the sample heating process.

An apparatus and method for heating a sample, such as chemical reaction mixtures are disclosed. The apparatus may include at least a microwave generator, a waveguide for guiding the generated microwaves to an applicator, and a deflector formed by a closed loop defining a plane. The deflector may have an inherent resonance frequency and a thickness in a direction normal to the plane. The deflector may be rotatable around an axis being at least substantially parallel to the plane, and positioned in the waveguide so as to form a resonant cavity with the sample and the waveguide applicator. The resonance conditions of the resonant cavity and the coupling factor of radiation from the waveguide to the cavity may be easily adjustable by rotating the deflector. The resonance conditions and the coupling factor may be adjusted in response to the dielectric properties of the sample in order to optimize the amount of absorbed power and thereby obtain control of the sample heating process.