Gaetano Marrocco

The art of UHF RFID antenna design: impedance-matching and size-reduction techniques

Radio-frequency identification technology, based on the reader/tag paradigm, is quickly permeating several aspects of everyday life. The electromagnetic research mainly concerns the design of tag antennas having high efficiency and small size, and suited to complex impedance matching to the embedded electronics. Starting from the available but fragmented open literature, this paper presents a homogeneous survey of relevant methodologies for the design of UHF passive tag antennas. Particular care is taken to illustrate, within a common framework, the basic concepts of the most-used design layouts. The design techniques are illustrated by means of many noncommercial examples.

Gain-optimized self-resonant meander line antennas for RFID applications

New meander line antennas with improved gain are proposed as low-profile self-resonant tags for application in passive radio frequency identification. Antenna shape and size is optimized by genetic algorithm, taking conductor losses into account. Examples are presented for application at 869 MHz with antennas of different materials and sizes.

RFID Technology for IoT-Based Personal Healthcare in Smart Spaces

The current evolution of the traditional medical model toward the participatory medicine can be boosted by the Internet of Things (IoT) paradigm involving sensors (environmental, wearable, and implanted) spread inside domestic environments with the purpose to monitor the users health and activate remote assistance. RF identification (RFID) technology is now mature to provide part of the IoT physical layer for the personal healthcare in smart environments through low-cost, energy-autonomous, and disposable sensors. It is here presented a survey on the state-of-the-art of RFID for application to body centric systems and for gathering information (temperature, humidity, and other gases) about the users living environment. Many available options are described up to the application level with some examples of RFID systems able to collect and process multichannel data about the human behavior in compliance with the power exposure and sanitary regulations. Open challenges and possible new research trends are finally discussed.

RFID Antennas for the UHF Remote Monitoring of Human Subjects

This paper addresses the design of passive and semi- passive transponder antennas for radio frequency identification applications involving the human body as the object to be tagged or bio-monitored. A planar tag antenna geometry, that is based on a suspended patch fed via a nested slot and is able to host sensors and electronics, is here introduced. Guidelines for conjugate impedance matching are given for different kinds of microchip transmitters, within power limitations as well as space constraints. Finally, the antenna matching performance is experimentally evaluated utilizing a body-tissue phantom.

Modeling, Design and Experimentation of Wearable RFID Sensor Tag

Design of effective wearable tags for UHF RFID applications involving persons is still an open challenge due to the strong interaction of the antenna with the human body which is responsible of impedance detuning and efficiency degradation. A new tag geometry combining folded conductors and tuning slots is here discussed through numerical analysis and extensive experimentation also including the integration of a passive motion detector. The achieved designs, having size comparable with a credit card, may be applied to any part of the body. The measured performance indicates a possible application of these body-worn tags for the continuous tracking of human movements in a conventional room.

Pervasive electromagnetics: sensing paradigms by passive RFID technology

Things equipped with electronic labels having both identification and sensing capability could naturally be turned into digital entities in the framework of the Internet of Things. Radio frequency identification (RFID) technology offers the natural background to achieve such functionalities, provided that the basic physics governing the sensing and electromagnetic interaction phenomena are fully exploited. The sensing of Things is here reviewed from an electromagnetic perspective with the purpose of showing how advanced performance may be achieved by means of low-cost batteryless devices. A possible classification of basic sensing modalities is introduced, and many ideas, at different stages of maturity, are then discussed with the help of examples ranging from the sensing of non-living Things up to the more challenging sensing of Humans.

Passive RFID Strain-Sensor Based on Meander-Line Antennas

The processing of backscattered signals coming from RFID tags is potentially useful to detect the physical state of the tagged object. It is here shown how to design a completely passive UHF RFID sensor for strain monitoring starting from a flexible meander-line dipole whose shape factor and feed section are engineered to achieve the desired sensing resolution and dynamic range. This class of devices is low-cost, promises sub-millimeter resolution and may found interesting applications in the Structural Health Monitoring of damaged structures and vehicles as well as during extreme and adverse events.

Multiport Sensor RFIDs for Wireless Passive Sensing of Objects—Basic Theory and Early Results

A new family of passive sensor radio-frequency identification devices is here proposed for applications in the context of wireless sensor networks. The new tags, working in the ultra-high frequency band, are able to detect the value or the change of some features of the tagged body without using any specific sensor. Such tags are provided with multiple chips embedded either within a cluster of cooperating antennas or in a single multiport antenna, and exploit the natural mismatch of the antenna input impedance caused by the change of the tagged object. A basic theory of multiport sensor tags is formulated with the purpose to describe the possible classification and detection performances in a unitary context. Some numerical examples and a first experiment corroborate the feasibility of the idea.

RFID Grids: Part I—Electromagnetic Theory

The close displacement of UHF RFID tags can be considered as an electromagnetic interconnected system having specific properties. The so denoted RFID Grid includes single-chip tags in close mutual proximity or a single tag with a multiplicity of embedded microchips. A multi-port scattering framework is used to derive the macroscopic parameters governing the system response which could be optimized for the specific application. Moreover, unique features are introduced, such as the possibility to improve the power scavenging and the generation of analog identifiers and fingerprint. The last ones are electromagnetic responses independent on the position and orientation of the reader and on the nearby environment, with great relevance for Sensing and Security.

Estimation of UHF RFID Reading Regions in Real Environments

The reading range is one of the most critical performance indicators of radio-frequency identification (RFID) systems. It depends on many physical and geometrical parameters. Typically, in the ultra-high-frequency band (UHF: 860 MHz to 960 MHz), the maximum size of the reading region is estimated by the free-space propagation model. This is based on the Friis formula, even if much more accurate predictions may be accomplished nowadays by time-consuming electromagnetic simulations, accounting for the antennas and the interaction with the nearby environment. This paper proposes a general parameterization of the three-dimensional reading region. This done having introduced all of the accessible system data, such as the emitted power, the reader and tag-over-object radiation patterns, and also the interrogation duty cycle, the scenario features, and the safety regulation constraints. Within this framework, the opportunity and some improvements of the free-space model are analyzed. They are compared with measurements and with more-accurate three-dimensional simulations of realistic environments. The discussion demonstrates the validity range of the free-space approximations, and evaluates the improvement achieved by including the main interactions with the environment. The derived formulas are ready to use and to be applied for the planning and optimization of reader-tag networks.