# Design and SAR Analysis of a Dual Band Wearable Antenna for WLAN Applications
## 1 Introduction
High impedance surfaces or EBG structures are used to minimize this degradation in performance [14]. EBG structures are artificial materials used as a ground plane for antennas. These structures enhance the overall performance of an antenna by providing in-phase reflection and surface wave suppression [19; 20; 21; 22]. Another aspect of EBG can be found in array antennas. Mutual coupling is a severe problem in array antennas or multiple antenna systems [23; 24]. This problem of mutual coupling between multiple antenna elements can be overcome by utilizing EBG [25; 26]. Instead of EBG, the same objective can be achieved by using defected ground structures (DGS) [27]. However, in some cases, as in [28], the gain of the array antenna may be significantly reduced by using DGS. Therefore, EBG is a better choice compared to DGS. In most of the work in literature, only flat antenna conditions are usually considered for the antenna performance [29] and SAR measurements [30; 31]. However, due to the flexibility of wearable antennas, it is not possible for these antennas to maintain their flat conditions all the time on a wearer's body. Moreover, the SAR value is a function of the bending radius of a specified body organ [32]; the smaller the bending radius, the worse the SAR value. Furthermore, crumpling and bending an antenna may reduce its performance, as reported in [33]. Therefore, in this paper, we provide a comprehensive SAR analysis as well as the impact of other antenna parameters on both flat and bending conditions. In addition, we consider antenna bending conditions based on various wearable antenna radii sizes specified on the basis of the corresponding human arms and legs on which they are wrapped. In this work, a very compact size dual band wearable microstrip patch antenna operating at 2.5 and 5.196 GHz is designed. In order to improve the performance of antenna in terms of directivity, gain and bandwidth, two types of EBG ground planes were designed for the proposed conventional antenna. The antenna is low profile and conformable and is composed of a textile material called polyethylene foam, having a relative permittivity of 1.05. The proposed antenna is bent around human legs and arms of different radii, and its operation is studied under various bent conditions. For the on-body simulation, two types of body phantoms are modeled. The first one is a flat body phantom (used for the chest) consisting of three layers, whereas the second one is a cylindrical body phantom (used for the arms and legs) consisting of four different layers. The proposed antenna is placed on the flat body phantom as well as bent around arms (of different radii) and legs, and its SAR analysis is carried out. We use CST MWS software for all the simulations and analysis in this work. The rest of the paper is organized into the following sections. Section 2 provides our design methodology using various approaches. In Section 3, we present the human phantom modeling approach and describe our simulation results based on off-body and on-body analyses. Furthermore, we thoroughly discuss the impact of various antenna positions. In Section 4, we conclude the paper and discuss some open questions.