Effects of weaving structures and parameters on the radiation properties of three-dimensional fabric integrated microstrip antennas

In smart textile systems, the wireless communication between the wearer and the wider environment plays an important role, especially in medical applications. This can be achieved by integrating an antenna in textile materials. The low-profile microstrip antenna is a desirable choice for textile antennas and integrating this type of antenna into the three-dimensional woven fabric achieves the most integrated textile antenna structure up to now. Different from traditional antenna structures, the three-dimensional woven fabric integrated microstrip antenna has the radiation patch and ground plane totally woven with the yarns, where the radiation properties would strongly depend on the weaving structures and parameters. In this paper, a 1.9 GHz single patch microstrip antenna was designed and six types of antennas with different combinations of woven patches and ground planes were compared. The measured results showed that the three-dimensional woven antenna had adequate performance. In addition, the three-dimensional woven antenna with warp yarns parallel to the feeding direction exhibited a better return loss and radiation pattern than the antenna with weft yarn parallel to the feeding direction, due to the longer current path for the latter antenna based on simulated current distribution analysis. Furthermore, the effects of conductive yarn parameters on the antenna properties were discussed and yarn structures were suggested to obtain relatively ideal antenna performances.