Swastika Slot UWB Antenna for Body-worn Application in WBAN Vivek Kumar Research Scholar: Dept. of ECE, Birla Institute of Technology, Mesra Ranchi, India mr.vivek.1988@ieee.org Bharat Gupta Associate Professor: Dept. of ECE, Birla Institute of Technology, Mesra Ranchi, India bharatg@bitmesra.ac.in Abstract— Advances in sensing, computing and communication technologies coupled with the need of cost reduction, and level of comfort have led to the development of Wireless Body Area Networks (WBAN). Ultra-wideband (UWB) technology is one of the fastest growing technologies for WBAN. The increasing demand of compact size, portable, body-worn, and lightweight electronic devices for the WBAN applications requires the design of miniature antennas. Therefore, in this paper, we present a novel swastika slot UWB antenna with the concept of modified ground plane. Furthermore, a swastika slot UWB antenna and its radiation characteristics over free space and body-worn (human phantom model) scenarios are simulated for WBAN applications. The antenna designed in such a way that it can give acceptable performance both over free space as well as body-worn scenarios without any prerequisite. Most importantly, we have analyzed the effect of specific absorption rate (SAR) on the human body due to the radiation of UWB antenna, considering the human body as homogeneous and layered heterogeneous phantom models. Keywords- Healthcare Monitor, Wireless Body Area Networks (WBAN), Body-worn antennas, Ultra wideband (UWB), Specific absorption rate (SAR), Human tissue. I. INTRODUCTION The body-worn antenna and body-centric communication systems has received much attention over the past few years for healthcare monitoring applications. Such systems are gained much concern for other applications such as sports and fitness, gaming, lifestyle and entertainment, military health. These applications have included WBAN, a highly localized wireless networks which gather information on entities of interest by multiple distributed sensor elements, to monitor the health condition pervasively and ubiquitously [1], [2]. An UWB technology is the one of the most anticipating solution for WBAN. In February, 2002, the Federal Communications Commission (FCC) amended the part 15 rules and releases the UWB standards. UWB covers a huge bandwidth of 7.5 GHz (from 3.1 GHz to 10.6 GHz) for communication. One of the main advantages of UWB technology is low power emission density (−41.3 dBm/MHz). UWB technology possesses a feature of variable data rate from few Kbps to Mbps. This features opened a new possibilities for potential application of UWB technology for healthcare, thus, ensuring low interference with other neighboring wireless devices [3]. Designing a body-worn antenna for body-centric communications would have to face several issues and challenges. The antenna needs to fulfill numerous desirable requirements, like small size, high radiation efficiency, occupy entire UWB frequency spectrum, better on-body propagation, and optimized characteristics in time and frequency domain [4]. The human body is complex structure comprised of several layers like skin, fat, muscle, and bone etc. These body layers have different dielectric constant, conductivity and thickness and acts as a non- uniform medium for RF wave propagation. Therefore depending upon the frequency of operation and most importantly presence of human body, which leads to high losses such as power absorption, destruction in antenna radiation pattern, shift in resonance frequency, reduced efficiency, and variations in feed- point impedance. The UWB technology and applications in healthcare field have been experiencing tremendous interests in both industrial and scientific research. However, there are still some hindrances (as discussed earlier), which restrict its full potential deployment. One of the important challenges in antenna design is to occupy the entire UWB frequency spectrum (from 3.1 GHz to10.6 GHz) with better radiation efficiency. The classical broadband antenna system such as dipole antenna [4], [5] exhibits lower complexity but lower bandwidth (narrowband) restrict its use towards such application where high data rate is prime necessity. Though the folded dipole antenna [6] has gained much concern over classical one, but the spurious radiation efficiency over entire spectrum is still open research challenges. Some other well-known antenna configuration such as vivaldi antenna and biconical antenna [7], [8] has also gained huge popularity. The directional approach (vivaldi antenna) and size (biconical antenna) limits it application for body-worn or implanted application for healthcare monitoring. Compact planar antennas have played a key role towards achieving desirable performance in portable and mobile applications. The concept of slotted ground plane with feed gap enhances the impedance bandwidth of antenna. The modified slotted ground plane acts as an impedance matching element. Since making slots can nullify the inductive behavior of patch by creating a capacitive load and thus achieving a wide bandwidth. In [8], the authors investigate the input impedance of two planar UWB antennas over human tissue model, in order to find shortest antenna-body operating distance.