Use of Rod Reflectors for SAR Reduction in Human Head

An improved version of the compensation method based on rod reflectors is presented. In this version, one or more metallic rod reflectors are installed near a transmitting antenna in order to create an additional field needed for decreasing the antenna's field inside the user's head, hence removing the need for auxiliary radiators. Both single and double rod reflectors are investigated. It is shown that using two rod reflectors, the field at the compensation point decreases by at least 7.5 dB in the frequency range of 850-2200 MHz. Using a single rod the reduction factor is above 5.4 dB in the same frequency band. Using the proposed rod-antenna structure with a single reflector, the peak specific absorption rate (SAR1g) and the total SAR measured at 1 GHz were reduced by 7.7 and 8.9 dB, respectively. With two reflectors, the SAR reduction factor for peak SAR (1 g) and total SAR levels were, respectively, 9.5 and 10.2 dB. The simulations and experimental results obtained so far show that the developed rod-antenna structures can be used as an effective method for SAR reduction.