978-1-5090-5306-3/16/$31.00 ©2016 IEEE Design of a 5.2 GHz Circularly Polarized Textile Patch Antenna for On/Off Body Radio Propagation Channel Evaluation M. Abdulmalek, N. Abdulaziz, H. Rahman Faculty of Engineering and Information Science, University of Wollongong in Dubai, Dubai, UAE. H. A. Rahim, M. Fie, P. J. Soh School of Computer and Communication Engineering, Universiti Malaysia Perlis, Pauh Putra, Arau, Perlis, Malaysia . Abstract— This paper presents a lightweight and simple structure of slotted circularly polarized (CP) patch antenna using conductive textile. ShieldIt Super is used as a conductive textile and felt is used as a substrate of the antenna. The prototype is designed with a total dimension of 36 mm × 36 mm and spaced by a 3 mm thick felt fabric for Body-centric Wireless Communication (BCWC) operating in the 5.2 GHz Industrial, Scientific and Medical (ISM) Hyper Local Area Network (LAN) band. A parametric study has been carried out in order to investigate the antenna basic characteristics, thereby enhancing the antenna performance. The proposed antenna is benchmarked against the without slot circularly polarized textile patch antenna. The measured results show that the slotted CP patch textile antenna produces better performance compared to the without the slot CP patch textile in terms of bandwidth with an acceptable 3-dB axial ratio bandwidth and gain. Keywords—component; Circularly polarized antenna; textile antenna; patch antenna; body-centric wireless communication; Hyper Local Area Network (HyperLAN); healthcare wireless system. I. INTRODUCTION The miniaturization of wearable hardware, embedded software, and digital signal processing has made it possible to integrate onto the human body. BCWC has been expanding in a wide range of fields, such as medical monitoring and sensing, emergency response, military, sports, and in the multimedia field [1-5]. An antenna with circular polarization is favoured over linear polarization for wireless on-body communication due to its independence of orientation. The axial ratio is an indicator of the quality of circular polarization and the circularly polarized antenna normally is being considered to have a good axial ratio when its value is below 3 dB. Modifications are necessary in ensuring a patch antenna to generate circular polarization such as cutting a notch at the opposite corners or having 90 o out phase feedings at orthogonal edges [6-7]. However, the drawbacks of these designs are complicated and have very limited bandwidth. On top of these, proximity of the human body and the narrow bandwidth of a patch due to bending condition may worsen the detuning effect by shifting the resonant frequency when the user is moving [8]. Consequently, the efficiency of healthcare monitoring system may degrade at the desired frequency. Limited work has been done in designing circularly polarized textile antennas where high performance wide-slot circularly polarized antennas have been proposed, e.g. by implementing annular ring slot [9], single-feed aperture coupled slotted [10] and coplanar waveguide fed (CPW) [8][11]. One effective method in producing high performance wide-slot circularly polarized antenna is the CPW-fed technique due to its robust tolerance on difference body’s conditions and single layer of metal usage. Despite its high performance, the main disadvantage of CPW-fed based technique is the missing ground plane on its topology, and thus causing higher frequency detuning effect due to the body coupling when the antenna is placed close to the human body. This work proposes a lightweight and robust against the human body which is made purely from the textile. This work aims to achieve broad impedance and axial ratio bandwidths so as to ensure its robustness to be implemented for BCWC application at 5.2 GHz HiperLAN, such as in-home healthcare wireless wearable sensor system. II. CIRCULARLY POLARIZED ALL-TEXTILE ANTENNA TOPOLOGY Two antenna topologies are investigated in this work which is with and without slot textile antennas. The geometries of with and without slot antennas, designed with a commercial electromagnetic solver, CST Microwave Studio software, are shown in Figure 1 (a) and (b). The proposed antenna uses ShieldIt Super textile with 0.17 mm thickness and conductivity σ =1.18x10 5 Sm -1 . ShieldIt Super is an electrotextile made by LessEMF Inc, where it is used for the conducting antenna parts. ShieldIt Super is a ripstop, woven polyester textile plated with copper and nickel with a thickness t of 0.17 mm and an estimated weight of 230 g/m 2 . Its surface resistance R s is smaller than 0.05 Ω/sq. The overall topology of the antenna consists of a full ground plane and a patch, sandwiched with a single layer of felt fabric that acts as its substrate. The felt fabric has a relative dielectric permittivity İ r = 1.44, with 3 mm thickness and loss tangent tanį = 0.044 [12].