Microwave heating device and method for operating a microwave heating device

A microwave heating device, comprising:

• a heating chamber which is designed to receive at least one product to be heated;
• a microwave generating system designed to generate microwaves and including at least two radiating portions that are adapted to radiate microwaves to the heating chamber, a radiated power being associated with the radiated microwaves and, in use, a share of radiated power being reflected by the heating chamber;
• and
• a control unit;
• the microwave generating system being configured to radiate, via the at least two radiating portions, respective microwaves having a same frequency and different phases, wherein one of the radiating portions can be taken as a reference radiating portion and the microwaves radiated by the other radiating portion(s) can have respective phase shift(s) from the microwaves radiated by the reference radiating portion, the frequency value and the phase shift value(s) defining an operational configuration of the microwave generating system, an energy efficiency being associated with each operational configuration, the energy efficiency being inversely related to a ratio of reflected power over radiated power;
• the control unit being configured to operate the microwave generating system and to change the frequency and the phase shift(s) of the microwaves radiated by the microwave generating system;
• the control unit being configured to obtain data of energy efficiency, as a function of operational configurations, relating to the at least one product to be heated;
• the control unit being configured to run a selection procedure, in which:
• an operating frequency is selected, the frequency selection being based on the obtained data of energy efficiency;
• a reference operational configuration is selected, being the operational configuration with the maximum energy efficiency at the selected operating frequency;
• a plurality of operational configurations are chosen, each one having the selected operating frequency and respective phase shift(s) that is/are chosen around the respective phase shift(s) of the reference operational configuration, the phase shift(s) of each operational configuration of said plurality having a phase shift distance from the respective phase shift(s) of the reference operational configuration, such that, in the space of the phase shifts, the reference operational configuration is surrounded by the operational configurations of said plurality;
• the control unit being configured to run a heating procedure, in which the microwave generating system is sequentially operated in said plurality of operational configurations chosen in the selection procedure.