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A four-port single radiator ultrawideband (UWB) multiple input–multiple output (MIMO) footwear antenna for wearable applications is presented. The antenna is printed on the flexible polyethylene foam, which can be easily integrated into the footwear. The antenna element (AE) consists of a circular patch that offers better impedance matching over the UWB range without the use of a feeding line. The four AEs are arranged across the four edges of common square-shaped ground to design the MIMO antenna. The presented antenna is analyzed in both flat and bent states. The antenna offers a bandwidth of 12 GHz (2–14 GHz) and isolation >15 dB in the flat state and >20 dB in the bent state. For specific absorption rate (SAR) analysis, the antenna is simulated for 1 g of tissue over a foot phantom, and it is found to be less than 1.6 W/kg at different frequencies within the UWB frequency range.
Jayant et al. (Mon,) studied this question.