Embroidery leaf-shaped dipole antenna for wearable communication system

Abstract

The fast development of technology and the demand of mobile wireless communication have increased due to the advancement of wearable devices. Industries are continuing to search for devices that are compact, robust, portable, unobtrusive, cost-effective and easy to use. The feature of fabric antenna technology is responding well to the current trend towards wearable and flexibility materials due to its flexibility and convenient to users. Therefore, this thesis focuses on designing and analysing the type of embroidery antenna using conductive threads. Embroidery is usually used in the clothing industry to incorporate complex patterns into garments. A leaf-shaped dipole textile antenna at Industrial, Scientific and Medical (ISM) band is chosen to be further investigated. The proposed dipole antenna is designed to operate at 2.45 GHz. The effect of conductive threads with three different types of stitching is analysed. The first type of stitching leaf-shaped dipole antenna is circular followed by vertical and horizontal stitch respectively. These three types of embroidery antenna are investigated in terms of bending, crumpling and wetness. From the return loss measurement, the antenna bandwidth with circular stitch shows better performance with optimum resonances compared to the vertical and horizontal stitching. The bandwidth of circular stitching for bending and crumpling investigation process shows 25% and 40% improved performance respectively. In wetness investigation, the presence of water has modified the properties of the substrate yields change in the operating frequency. The antenna performance after the wetness is not as similar to the earlier state (before wetness experiment) due to the shrinking effect and slight property changes on the fabric material. The measured results confirm that the circular stitch is more suitable for leaf-shaped dipole antenna design. Thus, it can be concluded that different stitches give different results for leaf-shaped dipole antenna. These results are in good agreement to the previous work where stitching types are important aspect to be taken into account to ensure good antenna performances.