Radio-frequency heating apparatus and radio-frequency heating method

A radio-frequency heating apparatus that heats an object placed in a heating chamber with radio-frequency power, said apparatus comprising:

• at least one radio-frequency power generation unit configured to generate radio-frequency power of a set frequency;
• a variable phase shift unit configured to change a phase of the radio-frequency power generated by said radio-frequency power generation unit;
• a plurality of radio-frequency power units each including (i) a radiation unit configured to radiate the radio-frequency power of a phase changed by said variable phase shift unit to the heating chamber, and (ii) a backward power detection unit configured to detect backward power constituting a part of the radio-frequency power radiated from said radiation unit and incident into said radiation unit from the heating chamber;
• and
• a control unit configured to set a frequency for said radio-frequency power generation unit and a phase shift amount for said variable phase shift unit,
• wherein said backward power detection unit is configured to:
• detect, in the frequency set for said radio-frequency power generation unit by said control unit, an amplitude and a phase of a reflected wave constituting the backward power inputted by reflection to said radiation unit of one of said radio-frequency power units, and an amplitude and a phase of a through wave constituting the backward power inputted to said radiation unit of the one of said radio-frequency power units, the reflected wave being part of the radio-frequency power radiated from said radiation unit of the one of said radio-frequency power units, and the through wave being part of the radio-frequency power radiated from a radiation unit of another one of said radio-frequency power units, and
• said control unit is configured to:
• (i) sequentially set a plurality of frequencies for said radio-frequency power generation unit, (ii) estimate by calculation an amplitude and a phase of the reflected wave and an amplitude and a phase of the through wave resulting from a given combination of the phase shift amounts in said variable phase shift unit, with respect to each of the frequencies that can be set for said radio-frequency power generation unit, by using, in said backward power detection unit of each of said radio-frequency power units, the amplitude and the phase of the reflected wave and the amplitude and the phase of the through wave with respect to each of the set frequencies, (iii) determine a frequency of the radio-frequency power to be generated by said radio-frequency power generation unit and a phase shift amount of said variable phase shift unit for heating the object such that a total amount of the reflected wave and the through wave of each of said radio-frequency power units is smallest from (a) the amplitude and the phase of the reflected wave and the amplitude and the phase of the through wave detected with respect to each of the frequencies, and (b) given combinations of the phase shift amounts in said variable phase shift unit, estimated with respect to each of the frequencies, and (iv) set the determined frequency and the determined phase shift amount for said radio-frequency power generation unit and said variable phase shift unit.