The following paper describes the valid optimization problem of multi-element circular array that contains 16 equal-length dipole antennas surrounding given two-spherical object. The task of the authors was to maximize the specific absorption rate (SAR) inside the inner object, while maintaining its minimum value in the external sphere. The proposed approach includes changes in the powers and phases of the voltage sources supplying individual dipoles of the antenna matrix. The shown method may have huge impact in localized tumor heating during thermal therapy.