The main objective of using microwave in hyperthermia for cancer therapy is to help achieve heating of deep-seated tumor without overheating the surrounding healthy tissue by utilizing the difference of the thermal sensitivity between tumor and normal tissue. The special requirements of antenna in living tissue are that antenna is small, produces confined near-field pattern, and presents low return loss at the input port to avoid excessive heating of the coaxial feed-line for the high input power. In this paper, an insulated monopole antenna with cap and balun at 2.45 GHz is designed for these purposes. The commercial numerical program is used to show characteristics of the designed antenna, and simulated results agrees well with the experimental results for which the infrared(IR) camera is used to measure the heat pattern in the biological tissue-equivalent phantom.
Measured data shows that well confined heat pattern which peaks at the middle of the monopole(broadside) and ties out smoothly at the both ends of the monopole(cap and balun). This antenna shows the input reflection coefficient of -30dB and the temperature of the tissue phantom rises linearly with input power peaks about 46℃ at the 20W RF input power.