Evaluation of HF Band NFC/RFID Antennas for Smart Shelf Applications Soheyl Soodmand 1 , Tim W. C. Brown 1 , Alexander Gluhak 1 1 Centre for Communication Systems Research, University of Surrey, Guildford, UK Abstract — a mass number of tagged items are predicted to be in use in future applications of HF RFID/NFC systems. One such application, where items such as books or other items contained on a shelf or in a cupboard, can use RFID technology to ascertain the position and logging of such items in addition to identifying their existence on the shelf hence defined as a smart shelf. In the first instance, a new theoretical approach is presented to increase bandwidth of RFID reader antennas operating at HF band to improve the reception of the backscattered RFID response. A prototype antenna is designed and evaluated by measurement for its capability in being used for smart shelf applications. The more bandwidth will support subcarrier frequencies for the all the existing HF RFID standards (ISO/IEC 15693 and ISO/IEC14443) to be detected more easily and thus leads to increased range of identification. Also, it is shown that in the presence of books, the HF RFID technology is capable of identifying the distance of a tag antenna based on the received H-field, which could be used in a smart shelf management system. Index Terms — Near-field radiation; Radio Frequency Identification Antennas (RFID antennas); Inductive Coupling I. INTRODUCTION A wireless system using radio frequency identification (RFID) consists of a reader/interrogator device and one or several transponders/tags. The RFID is a technology that communicates through radio waves to transfer data between the reader and the tag attached to an object for the purpose of identification and tracking. The rapid proliferation of passive RFID tags in the past decade has given rise to various concepts that integrate the physical world with the virtual one. One of the most popular is Internet of Things (IoT), a vision in which the Internet extends into our everyday lives through a wireless network of uniquely identifiable objects i.e. the IoT refers to uniquely identifiable objects (things) and their virtual representations in an Internet-like structure. If all objects of daily life were equipped with the RFID tags, they could be identified and inventoried by computers [1, 2]. In this type of RFID system, each physical object is accompanied by a rich, globally accessible virtual object that contains both current and historical information on that object’s physical properties, origin, ownership, and sensory context. Smart RFID reader systems are building blocks for the IoT [3] and recently the RFID smart-shelf system has received much attention because of increasing demands for large scale item-level management such as grocery products in the retail supply chain, large volumes of books in libraries and important documentation in offices [4-7]. Most of the previous works address the RFID application on the performance of ultra high frequency (UHF) band and less have been reported that are relevant to high frequency (HF) applications which use inductive coupling to operate i.e. HF RFID [8]. HF RFID technology has an operation range of up to 1~2 meters and has good performance in a crowded environment when compared with UHF RFID because the magnetic field is not affected by most of the surrounding dielectric materials [9]. In the recent two years renewed interest and rapid progress has been made in the application of HF RFID for the IoT purposes [10]. Numerous predictions are given that we’ll have hundreds of billions of RFID-tagged objects at approximately five cents per tag by 2015 [11]. Communications in such a crowded vast group of tags/readers as well as having more data transfer necessitate the need for reliable antenna to create smart RFID stock management, so a new design of HF RFID reader antennas is a critical issue. Bandwidth increment of HF RFID antennas will cause easier detection of subcarrier frequencies and thus increased range of identification. In this paper an approach to increase the bandwidth of HF RFID antennas is presented and then implemented in a prototype antenna. Better range of receiving subcarrier frequencies for the all of the existing HF RFID standards (ISO/IEC 15693 and ISO/IEC 14443) is obtained. The capability of the antenna to identify position of book is investigated. Good results are obtained for the received H-field by the tag and also return loss of the enhanced bandwidth reader antenna. The presented antenna is a suitable candidate to be used in a HF RFID smart shelf system. II. AN APPROACH TO INCREASE BANDWIDTH OF HF RFID ANTENNAS Previously, a procedure similar to the design of a bandpass filter is used to synthesize the matching network [12], for example 0.5λ or 0.25λ stubs are used at the input of antennas to increase their bandwidth [12-15]. Because 0.5λ or 0.25λ stubs have big length values at HF band it is nearly impossible to use them in a practical HF RFID antenna input in order to increase bandwidth. For example for a HF RFID antenna operating at 13.56 MHz frequency, the wavelength (λ) is about 22.5 m while the dimension of conventional HF RFID antenna is about 1 meter [16, 17], so with due attention to the volume limitations, using equivalent lumped elements of the stubs as a bandpass filter at input of the HF RFID antenna seems a better choice to achieve bandwidth increment. 978-88-907018-3-2/13 ©2013 IEEE 2013 7th European Conference on Antennas and Propagation (EuCAP) 1895