A method of coherently controlling irradiation of an object in an enclosed cavity by at least two radio frequency (RF) feeds includes setting an amplitude, a phase and a frequency for each of the RF feeds; actuating all of the RF feeds with the respectively set amplitudes, phases and frequencies to irradiate the object; measuring a reflected power at each of the RF feeds; characterizing a complete scattering parameter matrix of the enclosed cavity while the object is being irradiated; and adjusting the power, the phase and the frequency for each of the RF feeds based on the complete scattering parameter matrix and values of the power, the phase and the frequency of the RF feeds before adjusting.