Microwave oven having resonant antenna

摘要

A circularly polarized microwave oven. Microwave energy is coupled from a waveguide above the ceiling to the cavity by a rotatable vertical probe extending through a circular aperture in the cavity. A strip conductor closely spaced to the ceiling to limit radiation therefrom conducts the microwave current to an air dielectric patch antenna radially offset from the axis of the probe. A vertical section of the strip conductor spaces the patch antenna more than one-eighth wavelength from the ceiling which functions as a ground plane. The patch antenna is rectangular and the dimensions of its sides are selected to be respectively resonant above and below the operating frequency of the oven. More specifically, the dimensions are selected so that the orthogonal currents parallel to the rectangle sides produce orthogonal radiated components that are equal in magnitude and separated by 90 DEG in phase. Accordingly, the resonant patch or flag antenna radiates substantially circular polarization. The probe is supported on a vertical post of a support cradle suspended from the ceiling and the patch antenna is rotated about the axis of the probe.