On-Body Reduced Size AMC Design for Lowering Specific Absorption Rate in Wearable Antenna Application

Abstract

This manuscript investigates the design parameters of an Artificial Magnetic Conductor (AMC) and their impact on the Specific Absorption Rate (SAR) when integrated with a Coplanar Waveguide (CPW) antenna. The AMC was designed with periodic square patches of 10 mm x 10 mm on a grounded dielectric substrate with a thickness of 1.6 mm and a dielectric constant of 4.4. The AMC design was optimized using CST Microwave Studio to achieve a 0-degree reflection phase at the operational frequency of 2.4 GHz. The optimization process involved varying the dimensions of the patches and the spacing between them to minimize return loss and maximize radiation efficiency. The CPW antenna, with and without the AMC, was simulated in the presence of a realistic human chest model to evaluate SAR levels. The results indicate that the introduction of the AMC improved the impedance matching of the antenna, reducing the reflection coefficient (S11) from -10 dB to -20 dB at 2.4 GHz. Furthermore, the integration of the AMC increased the antenna gain from 2 dBi to 5 dBi. Most importantly, the peak SAR value in the human chest model was reduced from 1.8 W/kg to 0.8 W/kg over 1g of tissue, demonstrating the AMC's effectiveness in lowering RF exposure to human tissues. These findings highlight the potential of AMCs in enhancing the performance and safety of wearable wireless devices by effectively reducing SAR levels while improving antenna efficiency.