Optimal design of focused arrays for microwave-induced hyperthermia

This study studies optimal design of focused antenna arrays for microwave-induced hyperthermia. The phases and amplitudes of the driving signals of array elements are determined by optimising the power transmission efficiency of the system consisting of the transmitting antenna array, a receiving antenna located in the target area, and an equivalent phantom representative of human tissues. On the basis of the proposed technique, a 4 x 2 focused patch array is designed to operate on a fat-mimicking phantom with working frequency at 433 MHz. The measured patterns for specific absorption rate indicate that the energy is focused in the desired spot and are in close agreement with simulations, which validate the optimisation method in a medium with low permittivity and low loss. A 4 x 3 focused patch array operating on a human body phantom with same working frequency is then designed, in which an air space and two additional dielectric layers have been introduced between the planar array and the body-mimicking phantom for impedance matching. A good focal performance at desired spot is also achieved, and the simulated and measured specific absorption rate patterns agree very well. This demonstrates the validity of the proposed design method in a medium with high permittivity and high loss.