Abstract: This disclosure relates to a microwave heating device and a method for operating a microwave heating device. The microwave heating device comprises at least two radiating portions that are adapted to radiate microwaves to the heating chamber and can be operated according to operational configurations that differ in frequency and/or in phase shift(s) between the radiated microwaves. A learning procedure can be executed in relation with at least one product positioned in the heating chamber. The learning procedure can be executed by changing frequency and phase shift(s) to sequentially operate the at least two radiating portions in a plurality of operational configurations, in such a way that, for each frequency, the at least two radiating portions are operated in a number of operational configurations that differ in phase shift(s) from one another. An energy efficiency can be calculated for each of said plurality of operational configurations and the obtained data are saved.

Abstract: A method and an apparatus for heating a food product constituted of a sandwich or the like, before it is consumed, in which the food product 4 is enclosed between at least a first heating element 6 and a second heating element 7 facing each other, the first heating element 6 comprising a first plurality 8 of electrically conductive raised elements 9 protruding towards the second heating element 7, and the second heating element 7 comprising a second plurality 10 of electrically conductive raised elements 9 protruding towards the first heating element 6, and is radio frequency heated using the raised elements 9 as electrodes 11, 12.