Low-SAR Antenna Design and Implementation for Mobile Phone Applications

This paper presents a novel approach for designing low-SAR (specific absorption rate) terminal antenna. First of all, the relationship between the magnetic field and the SAR value is deduced by using the electric field formula of SAR and Maxwell's equations. Then, by using the boundary conditions of the medium, the interaction mechanism between the radiated magnetic field of the antenna and the magnetic field inside human tissue is studied. Next, the relationship between the surface current and the radiated magnetic field of antenna is constructed. The approach of reducing the antenna radiated magnetic field is proposed by directly adjusting the antenna surface current, so that the SAR of human tissues is reduced. Finally, two low-SAR antennas are designed according to the proposed approach. The simulation and measurement results of the two low-SAR antennas show that the -6 dB bandwidth of both antennas is 2.4-2.49 GHz, which can meet the 2.4 G WLAN frequency band. At the same time, compared with the reference antenna, the peak values of 10 g average SAR of two antennas are reduced by more than 30%. In addition, the measured efficiencies of the two low-SAR antennas are higher than 40% in the operating frequency range. The validity of the proposed approach is proved by the simulation and measurement results of the antenna, which can be used to guide the SAR reduction design of mobile terminal antennas.