Compact Cavity-Backed Antenna on Textile in Substrate Integrated Waveguide (SIW) Technology Riccardo Moro, Maurizio Bozzi Dept. Electrical, Computer and Biomedical Engineering University of Pavia Pavia, Italy riccardo.moro@unipv.it, maurizio.bozzi@unipv.it Sam Agneessens, Hendrik Rogier Department of Information Technology-IMEC Ghent University Ghent, Belgium sam.agneessens@intec.ugent.be, hendrik.rogier@ugent.be Abstract— In this paper a folded cavity-backed patch antenna implemented in substrate integrated waveguide (SIW) technology is presented. The antenna has been designed to operate at 2.45 GHz, in the industrial, scientific and medical (ISM) frequency band, and a textile substrate has been adopted for the realization of the component. This topology of textile antenna could be useful for the monitoring of the activities of rescue workers in emergency situations such as the localization of fire- fighters, and the communication in critical operations. The proposed antenna has been experimentally verified: the response of the antenna exhibits a small frequency shift, caused by a discrepancy between the nominal and the real value of electrical permittivity of the textile substrate. The measured radiation characteristics of the antenna show a good agreement with simulations, and a measured radiation efficiency of approximately 70%. Keywords—Substrate integrated waveguide; textile material; new and emerging technologies and materials; cavity-backed antennas; wearable antennas. I. INTRODUCTION In the last years, textile on-body radio systems have received an increasing interest and, nowadays, they represent an important field of research. In particular, different antenna typologies fabricated on textile materials were proposed in order to achieve not only good electromagnetic performance, but also robust and comfortable systems [1]. Applications such as the tracking of the position of rescue workers and the communication with fire-fighters in critical conditions motivate the research towards novel efficient radio systems. A key point in rescue operations is the monitoring of body functions of the fire-fighters together with the characteristics of the external environment. All the data collected by the sensors integrated in the suit of rescue worker should be transmitted in order to evaluate in real time the risk of the rescue operation. For this reason the system of communication requires an antenna which should assure sufficiently large bandwidth and high radiation efficiency. Moreover, the antenna should be integrated into jackets of fire-fighters but it should not disturb their movements. The use of textile materials as substrate enables the fabrication of light and flexible components which are, at the same time, robust and reliable, and which can be easily integrated into garments [2]. A variety of patch antennas on textile, operating in the ISM band (2.4–2.4835 GHz), have been proposed [1,3]. Recently an SIW cavity-backed slot antenna was presented, demonstrating the feasibility of combining the fabrication of textile components with substrate integrated waveguide technology (Fig. 1) [4]. The SIW technology permits to integrate into a single substrate different components such as passive and active devices, as well as antennas. Therefore, in an entire system, the number of transitions between elements is limited and a reduction of losses is guaranteed [5]. Furthermore, by adopting SIW technology, we increase the efficiency and minimize the physical dimensions of the complete system. The choice of the substrate integrated waveguide technology for the implementation of the proposed antenna is motivated by the simple and low cost fabrication process and by its potential to easily realize multilayer structures. Moreover, the characteristics of SIW structures appear suitable for implementation of components on textile material because the flexibility of the substrate is preserved and conformal structure can be fabricated. In this paper a folded cavity-backed patch antenna realized in substrate integrated waveguide technology is presented. The integration of a patch antenna in an SIW cavity allows to reduce the surface wave effects and, consequently, to increase the radiation efficiency. In addition, thanks to the structure of the cavity, the designed antenna exhibits a high front-to-back ratio, which is an essential property for limiting the radiation towards the fire-fighter body. The proposed folded SIW cavity-backed patch antenna was fabricated: it results Fig. 1. Photograph of the SIW cavity-backed slot antenna (from [4]). 71.5mm 978-2-87487-031-6  2013 EuMA 7 -10 Oct 2013, Nuremberg, Germany Proceedings of the 43rd European Microwave Conference 1007