Triple Band Fractal Koch Antenna for Wearable Application

This report presents Triple-band Fractal Koch Textile antenna using flrst iteration of Koch geometry of a dipole antenna structure for wearable applications. In order to reduce the overall length of the dipole antenna structure, the ∞are angle of the antenna design is varied to three difierent values which are 30, 45 and 60 degree respectively. The radiating elements of the antenna are made of adhesive copper fabric, whilst the substrate is given a property of denim textile material. The proposed antennas are simulated in CST Studio and have been optimized to operate within the ISM frequency bands (0.902{0.928GHz, 2.4{2.5GHz and 5.725{5.875GHz). The simulation results are then compared with valid measurements and the results are further discussed in this paper. 1. INTRODUCTION Development of wearable application systems have been rapidly increased within the area of wire- less communications technology. The integration between mobile electronic devices and sensors with wireless technology enable good growth for wearable applications. The wearable applications are widely used in the paramedic, monitoring, flre flghter and military sector for tracking, navi- gation, mobile computing and data collection activities. Nowadays, the performances of wearable devices are optimized by compact size, movable and robust. For example, body centric wireless communications are developed in medical applications. There are three types of communication systems, these are in-body, on-body and ofi-body (1,2). The properties of the antenna such as compact size, simple fabrications, mechanical ∞exibility, comfort to the user and low cost are the main requirements for all modern wearable application system (3). Many new designs of wearable antennas are developed by other researchers such as patches, button, wired and conductive tex- tiles (4). Textile antennas are proposed for wearable antenna because they can be easily integrated with clothing. A number of researches have working on designing various type of textile antenna for wearable applications such as planar, dipole, monopole and microstrip patch antenna. The size of the antenna became the main issue on the wearable antenna. The antenna must have a compact size while maintaining the antenna's performance. In order to produce a compact size antenna, fractal Koch antenna is introduced for size reduction (5). 2. MATERIAL AND METHOD The wearable, durable and ∞exible conductive materials are the most important aspect for textile antenna. A good material has the ability to overcome the impact of bending and can operate properly in close proximity to the human body. Permittivity and loss tangent are critical parameters to be considered when selecting material. Normally, textile materials have low dielectric constant which can reduce the surface wave loss and improving the impedance bandwidth of antenna. Denim textile, which has thickness of 0.78mm is proposed as the substrate for this wearable antenna. The permittivity of denim textile is 1.7 and the loss tangent is 0.025. The proposed textile antenna consists of conductive textile which is an adhesive conductive fabric as the radiating element and a non-conductive textile while denim fabric as the substrate. Technically, the conductive fabric is attached on the denim textile using iron with controlled temperature.