Estudo de metamaterial têxtil para aplicação em substrato de antenas planares para tecnologia WBAN

Abstract

The constant development of implanted or wearable biometric sensors provided a increase of WBAN (Wireless Body Area Network) technology. WBAN can be used for many applications, such as physiological signal monitoring and industrial communication applications. In this context, the textile antenna is an important element in wireless communication in smart fabrics, being the object of recurrent research in industrial, military and medical applications. These antennas are flexible and, for this reason, it is convenient in applications where the rigidity of traditional antennas is considered an obstacle. The use of metamaterials in antennas can provide, among other characteristics, reduction of SAR (Specific Absorption Rate) and miniaturization of the device, important parameters for medical applications. This work presents the development of planar antennas with textile metamaterial substrate in the 5G frequency range for WBAN applications, showing since the substrate manufacture until antenna manufacturing and testing. Three types of textile substrate with different structure and composition were selected, and in each of them a conductive thread was inserted using different techniques (manual insertion, knitting and automatic sewing). The characterization of the materials was carried using simulations in HFSS® and the coaxial probe method, to obtain the electrical parameters. The antennas were designed and simulated to operate at 2.45 GHz and 3.5 GHz, with the best results being manufactured and tested in a Vector Network Analyzer (ARV). The results obtained in the simulations and tests were analyzed and the presence of metamaterial characteristic in the loop and straight stitch geometries was verified. The antennas with textile metamaterial substrate had a lower resonant frequency compared to those with a dielectric textile substrate, indicating the possibility of reducing device dimensions. Furthermore, after being curved and placed close to the human body, the antennas had a good performance, resonating below -10 dB with bandwidth above 2%.