Design of Passive RFID Sensor Tags Enhanced by a Novel Logical Communication Procedure over LLRP

Over the past decade, electromagnetic and communication science societies, along with improving the classical RFID technology, have put in a great deal of effort in designing novel and more complex UHF RFID tags with augmented capabilities. Novel tags offer additional functionalities besides identification by embedding sensors, actuators, and processing units. In this work an enhanced version of one of such devices, called SPARTACUS, is presented. While being completely passive, it conjugates identification, sensing, local computing, and actuation control and enables a proactive communication with any standard RFID reader. The paper presents details on a novel logical communication procedure over Low Level Reader Protocol (LLRP), besides discussing system validation and performance evaluation

Smart Prototyping Techniques for UHF RFID Tags: Electromagnetic Characterization and Comparison with Traditional Approaches

Over the last few years, the active and growing interest in Radiofrequency Identification (RFID) technology has stimulated a conspicuous research activity involving design and realization of passive label-type UHF RFID tags customized for specific applications. In most of the literature, presented and discussed tags are prototyped by using either rough-and-ready procedures or photolithography techniques on rigid Printed Circuit Boards. However, for several reasons, such approaches are not the most recommended, in particular they are rather time-consuming and, moreover, they give rise to low quality devices in one case, and to cumbersome and rigid tags in the other. In this work, two alternative prototyping techniques suitable for cost-effective, time-saving and high-performance built-in-lab tags are introduced and discussed. The former is based on the joint use of flexible PCBs and solid ink printers. The latter makes use of a cutting plotter to precisely shape the tag antenna on thin copper sheets. Afterwards, a selection of tags, designed and manufactured by using both traditional and alternative techniques, is rigorously characterized from the electromagnetic point of view in terms of input impedance and whole tag sensitivity by means of appropriate measurement setups. Results are then compared, thus guiding the tag designer towards the most appropriate technique on the basis of specific needs

Durability of Wearable Antennas Based on Nonwoven Conductive Fabrics: Experimental Study on Resistance to Washing and Ironing

Adhesive nonwoven conductive fabrics are appealing materials for fabricating fully textile antennas for wearable wireless systems. Wearable antennas should be flexible, lightweight, and mechanically resistant. Additionally, the antenna performance should be robust to activities related to daily use of garments, such as washing and ironing. Accordingly, in this work, the results of several washing tests performed on fully textile antennas fabricated by exploiting three different adhesive nonwoven conductive fabrics are reported

A Network Approach for Wireless Resonant Energy Links Using Relay Resonators

In this paper, a network approach for the analysis of a wireless resonant energy link consisting of N inductively coupled LC resonators is proposed. By using an artificial transmission line approach, the wireless link is modeled as a transmission line described by effective parameters. It is shown that the analyzed system exhibits a passband filter behavior. More specifically, the reported results demonstrate that in the wireless link passband the effective parameters assume negative values resulting in a negative phase delay. Useful design formulas are derived and validated by comparisons with the experimental data

A Wearable Wireless Energy Link for Thin-Film Batteries Charging

A wireless charger for low capacity thin-film batteries is presented. The proposed device consists of a nonradiative wireless resonant energy link and a power management unit. Experimental data referring to a prototype operating in the ISM band centered at 434 MHz are presented and discussed. In more detail, in order to facilitate the integration into wearable accessories (such as handbags or suitcases), the prototype of the wireless energy link was implemented by exploiting a magnetic coupling between two planar resonators fabricated by using a conductive fabric on a layer of leather. From experimental data, it is demonstrated that, at 434 MHz, the RF-to-RF power transfer efficiency of the link is approximately 69.3%. As for the performance of the system as a whole, when an RF power of 7.5 dBm is provided at the input port, a total efficiency of about 29.7% is obtained. Finally, experiments performed for calculating the charging time for a low capacity thin-film battery demonstrated that, for RF input power higher than 6 dBm, the time necessary for recharging the battery is lower than 50 minutes

Electromagnetic Performance Estimation of UHF RFID Tags in Harsh Contexts

Radio-Frequency Identification (RFID) technology is a consolidated example of electromagnetic system in which passive labels equipped with flexible antennas, called tags, are able to use a portion of the electromagnetic energy from the reader antennas, power-up their internal circuitry and provide the automatic identification of objects. Being fully-passive, the performance of RFID tags is strongly dependent on the context, so that the selection of the most suitable tag for the specific application becomes a key point. In this work, a cost-effective but accurate system for the over-the-air electromagnetic characterization of assembled UHF RFID tags is firstly presented and then validated through comparison with a consolidated and diffused measurement systems. Moreover, challenging use-cases demonstrating the usefulness of the proposed systems in analyzing the electromagnetic performance of label-type tags also when applied on materials on different shape or embedded into concrete blocks have been carried out

On the use of a reliable low-cost set-up for characterization measurements of antennas

In this paper, a low-cost time domain-based approach to antenna characterization is presented. The goal is to prove that time domain-based antenna measurements, after appropriate processing, represent an accurate and more practicable alternative to the universally accepted (yet highly expensive) antenna measurements in anechoic chamber, and provide information just as complete. Measurements on two commercial antennas are carried out in the time domain (in a non-controlled environment) and in the frequency domain (in an anechoic chamber): experimental data obtained from the two approaches are compared in terms of Return Loss. Results show that reliable results can be extracted from time domain data, and that a good insight into the antenna characteristics can be obtained even without using highly expensive facilities

Using Battery-Less RFID Tags with Augmented Capabilities in the Internet of Things

Driven by user demand for new smart systems in the framework of the Internet of Things (IoT) and fueled by technological advances in Radiofrequency Identification (RFID), an increasing number of new IoT-oriented RFID-based devices has appeared in recent years in scientific literature. Some of them conjugate canonical RFID identification with extra functionalities such as sensing, reasoning, memorization, and actuation. In this way, IoT challenging applications can be developed, which distribute processing load till to the extreme nodes of the network, while lying upon the well-established RFID infrastructure. In this work, a reasoned panoramic on the potentialities in the IoT framework of augmented RFID tags is presented and classified. Two applicative scenarios are envisioned, presented and discussed, to illustrate how augmented RFID devices may support advanced IoT systems