BACKGROUND

The present device generally relates to a method and device for electromagnetic cooking, and more specifically, to a method and device for determining and controlling the resonant modes within a microwave oven.

A conventional microwave oven cooks food by a process of dielectric heating in which a high-frequency alternating electromagnetic field is distributed throughout an enclosed cavity. A sub-band of the radio frequency spectrum, microwave frequencies at or around 2.45 GHz cause dielectric heating primarily by absorption of energy in water.

To generate microwave frequency radiation in a conventional microwave, a voltage applied to a high-voltage transformer results in a high-voltage power that is applied to a magnetron that generates microwave frequency radiation. The microwaves are then transmitted to an enclosed cavity containing the food through a waveguide. Cooking food in an enclosed cavity with a single, non-coherent source like a magnetron can result in non-uniform heating of the food. To more evenly heat food, microwave ovens include, among other things, mechanical solutions such as a microwave stirrer and a turntable for rotating the food. A common magnetron-based microwave source is not narrowband and not tunable (i.e. emits microwaves at a frequency that is changing over time and not selectable). As an alternative to such a common magnetron-based microwave source, solid-state sources can be included in microwave ovens which are tunable and coherent.

SUMMARY

According to one aspect of the present invention, an electromagnetic cooking device is provided having a cavity in which a liquid is placed and a plurality of RF feeds configured to introduce electromagnetic radiation into the cavity for heating the liquid. A controller is provided and is configured to: analyze forward and backward power at the plurality of RF feeds to calculate efficiency; determine and monitor a coefficient of variation of the efficiency; detect a boiling state in the liquid based on changes in the coefficient of variation; and adjust a power level of the electromagnetic radiation in response to detection of the boiling state to prevent the liquid from splattering.

According to another aspect of the present invention, a method of controlling cooking in an electromagnetic cooking device is provided. The electromagnetic cooking device has a cavity in which a liquid is placed and a plurality of RF feeds configured to introduce electromagnetic radiation into the cavity to heat the liquid. The method includes the steps of: analyzing forward and backward power at the plurality of RF feeds to calculate efficiency; determining and monitoring a coefficient of variation of the efficiency; detecting a boiling state in the liquid based on changes in the coefficient of variation; and adjusting a power level of the electromagnetic radiation in response to detection of the boiling state to prevent the liquid from splattering.

According to yet another aspect of the present invention, an electromagnetic cooking device is provided having a cavity in which a liquid is placed and a plurality of RF feeds configured to introduce electromagnetic radiation into the cavity for heating the liquid. A controller is provided and is configured to: analyze forward and backward power at the plurality of RF feeds to calculate efficiency; determine and monitor a coefficient of variation of the efficiency; detect a boiling state in the liquid based on the coefficient of variation satisfying a threshold condition; and adjust a power level of the electromagnetic radiation in response to detection of the boiling state to prevent the liquid from splattering.

