A simple estimation and verification technique for electrical characterization of textiles

In this paper, a simple method to estimate the relative permittivity ε_r and the tangential loss tan(δ) of wearable textiles is presented. Quarter-wavelength stub-line band-stop filters, based on jeans and cordura textiles, are designed assuming reasonable initial values of ε_r and tan(δ), fabricated and experimentally tested. The filter designs are then re-simulated, by tweaking the values ofε_r and tan(δ), until the computed results are matched to the already obtained measured ones. The parameters ε_r and tan(δ) of the jeans textile are studied in the 800MHz band. Results indicate that the difference between their initial values and the obtained actual estimates is large in this band. The study is repeated for both jeans and cordura textiles in the 2.4 GHz band. In this band of interest, the deviation of the initial ε_r and tan(δ) from their actual values is small. To verify the reliability of the obtained estimates, jeans- and cordura-based wearable antennas are designed for operation in the 2.4 GHz band. Prototypes of these antennas are fabricated. A good agreement between measured and simulated results is revealed, thus verifying the correctness of the proposed electrical characterization method.