Microwave feeding system

A microwave feeding system for a microwave oven or an oven with microwave heating function, said feeding system being disposed in a wall of an oven cavity and comprising:

• a magnetron, a rectangular wave guide and a cylindrical cavity all made of metal and all connected in series, the magnetron having a magnetron antenna that penetrates into the rectangular wave guide,
• a rotational omnidirectional quadrupole antenna arranged inside said cylindrical cavity and having a rotation axis corresponding with a symmetry axis of said cylindrical cavity, said antenna being driven by a motor arranged above the cylindrical cavity, a shaft interconnecting said motor and said antenna, said antenna and said shaft both being formed from metal, said antenna having four coplanar blades extending in a plane that is parallel to a longitudinal axis of said rectangular wave guide and perpendicular to said rotation axis, said antenna in operation being effective to act as a continuous phase shifter for microwaves in said cylindrical cavity, an inner diameter of said cylindrical cavity being 1.5-2 times a wavelength of said microwaves to be guided within said cylindrical cavity;
• an inner cavity formed as a cylindrical metal barrel and arranged inside said cylindrical cavity, said inner cavity being coaxial to said cylindrical cavity and enclosing said shaft, an inner diameter of said inner cavity being 2-4 times a diameter of said shaft;
• and
• a choke filter having a cylindrical shape and being arranged between said motor and said cylindrical cavity, said choke filter being coaxial to said cylindrical cavity;
• wherein in operation the microwaves emanating from said cylindrical cavity into said oven cavity are elliptically polarized TEM electromagnetic waves whose electric field vector extends parallel to a bottom wall of the oven cavity;
• and wherein in operation an efficiency of real power absorbed by a load within said oven cavity relative to microwave power delivered by the magnetron is more than 80%.