Signal generators for electromagnetic heating and systems and methods of providing thereof

A signal generator comprising:

• a plurality of voltage sources for generating a plurality of source signals;
• a plurality of switch groups for converting the plurality of source signals into a plurality of modulated signals by actuating one or more switches of the plurality of switch groups, the plurality of modulated signals being capable of providing a desired power spectral density;
• at least one switch network driver for providing a plurality of modulation signals to the plurality of switch groups, the one or more switches of the switch groups being actuated by the plurality of modulation signals;
• a signal combining unit comprising at least one transformer, the signal combining unit for combining one or more of the plurality of modulated signals into a combined signal and transforming the combined signal to have the desired power spectral density, thereby providing at least one output signal;
• and
• a processor configured to:
• determine a desired output signal having the desired power spectral density;
• and
• control the plurality of voltage sources, the at least one switch network driver, and the signal combining unit based on the desired output signal;
• wherein when the at least one output signal is applied to a load having a frequency-dependent impedance, at least one standing electromagnetic wave is produced along a length of the load, the at least one standing electromagnetic wave comprises at least a partial standing electromagnetic wave.