Design and relative permittivity determination of an EBG-based wearable antenna

This paper presents a simple technique for determining the permittivity of a textile material, and the use of this material in the design of a wearable antenna based on Electromag- netic Band Gap (EBG) structures. Finding the permittivity of some types of textile is usually a challenge. Knowing the exact permittivity value is very important to prevent the operation frequency of textile-based antennas from deviating from the intended design frequency. A patch antenna that resonates at 1.575GHz is designed on a Cordura fabric dielectric material, assuming a permittivity ("r) of 1.9. Copper tapes are used as the conductive material. In the design, an EBG layer is incorporated halfway between the patch and the ground plane. A prototype of the designed antenna is fabricated, and its re∞ection coe-cient measured. Results show a shift in the resonant frequency to 1.74GHz, implying a lower substrate permittivity than originally assumed. The same design is simulated for several values of "r and the attained results show resonance at 1.74GHz for a permittivity of 1.5. The patch is then redesigned for 1.575GHz taking "r = 1:5, where the measurements of the newly fabricated prototype show agreement with the simulated ones.