Design and Implementation of an E-Textile SSPP-Based Low-Pass Filter for Advanced Wearable Applications

This paper presents the design and implementation of an electronic textile (e-textile) low-pass filter (LPF) based on Spoof Surface Plasmon Polaritons (SSPPs), achieving a cutoff frequency of 6.47 GHz for advanced wearable applications. The proposed filter comprises m-shaped unit cells designed to be patterned on the top side of a denim substrate, complemented by a complete ground plane on the back side. The dimensions of the filter are $2.15 \lambda_{0} \times 0.539 \lambda_{0} \times 0.034 \lambda_{0}$, where $\lambda_{0}$ is the wavelength corresponding to the cutoff frequency. Simulation results reveal a passband frequency range extending from 0 GHz to 6.47 GHz, with a -10 dB impedance bandwidth of 6.47 GHz and a stopband attenuation of -45 dB at 6.90 GHz. The filter demonstrates low insertion loss within the passband, with a maximum value of just 0.8 dB. Finally, the Specific Absorption Rate (SAR) values of $0.0268 \mathrm{~W} / \mathrm{kg}$ and 0.0125 $\mathrm{W} / \mathrm{kg}$ for both the 1 g and 10 g standards, respectively indicate compliance with safety regulations, affirming its suitability for wearable applications on the human body. The e-textile design and SAR analysis ensure that the filter remains both flexible and comfortable, making it well-suited for integration into smart clothing and other wearable devices.