Auto-load impedance matching device of a microwave oven

A microwave oven comprising:

• a heating chamber having a side wall and a bottom surface;
• at least one opening in said side wall of the heating chamber;
• a wave guide located at said side wall of the heating chamber;
• a turntable mounted above said bottom surface of the heating chamber for placing food thereon, said turntable being rotatable by a turntable driving means located beneath the heating chamber;
• key signal input means for receiving external key signals from a user and providing a first output;
• load sensing means for sensing a load of food in the heating chamber and providing a second output;
• matching means movably mounted in the wave guide;
• power supply means;
• driving means for moving said matching means;
• a microcomputer for controlling the power supply means and the driving means in response to said first and second outputs of the key signal input means and the load sensing means, respectively;
• a magnetron driven by the power supply means for generating microwaves to be directed into the heating chamber through the wave guide and through said at least one opening;
• a variable vane mounted in one opening of the heating chamber;
• and
• a variable vane driving means for turning the variable vane at a predetermined angle under the control of the microcomputer in response to said second output of the load sensing means.