Specific Absorption Rate (SAR) Evaluation of Textile Antennas

This paper presents a detailed and systematic investigation of the reproducibility of specific absorption rate (SAR) measurements using textile antennas and their simulation accuracy. The ability to accurately predict the SAR is very important for practical textile antenna designers since certified SAR measurements are costly. To that goal, the SAR values of a range of textile antennas operating in various bands of the IEEE 802.15.6 and 802.11 standards are evaluated. The selected textile antenna topologies for the evaluation differ in terms of the bandwidth behavior (broadband, dual band, and ultrawideband). They are chosen to be distinct, have been fabricated using an array of conductive textiles, and are benchmarked against similar structures made from a flexible conductor. SAR values are evaluated at three different frequencies, i.e., 2.45, 5.2, and 5.8 GHz, respectively, using a commercial electromagnetic solver and a certified experimental setup. Factors affecting the SAR behavior are presented and discussed. Results indicate that antennas without a rear ground plane are producing almost three times the SAR of textile antennas that feature a full ground plane. The results of this paper point out that the repeatability of the measurements is about 10% and that the agreement between simulations and measurements is on the order of about 17%.