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Numerical and Experimental Characterization of Wrist-Fingers Communication Link for RFID-based Finger Augmented Devices

S. Amendola, V. Di Cecco, and G. Marrocco, IEEE Transactions on Antennas and Propagation, October 2018

Radiofrequency-Identification Finger-Augmented Devices (R-FAD) identify a particular wearable technology suitable to turn the human fingers into enhanced sensing surfaces to restore lost senses in impaired people as well as to augment the existing ones. The communication channel of R-FAD, involving a reader’s antenna placed onto the wrist and tag antennas stuck onto the fingers, is here characterized in the UHF RFID band by means of both numerical simulations, accounting for several options of the system, and an experimental campaign with volunteers asked to reproduce natural gestures of the hands. The study identifies the most appropriate placement of the devices and, above all, it quantifies the robustness of the link against the human variability. The channel follows a Lognormal Cumulative probability law indicating that the minimum required power to establish a reliable RFID link is 18-27 dBm depending on the chip sensitivity. Measurements finally revealed a remarkable correlation of the minimum required power from the reader with the volume of the hand.

Design and Experimentation of a Batteryless On-skin RFID Graphene-Oxide Sensor for the Monitoring and Discrimination of Breath Anomalies

M. C. Caccami, M. Y. S. Mulla, C. Occhiuzzi, C. Di Natale, and G. Marrocco, IEEE Sensors Journal, August 2018

Real-time and comfortable monitoring of the human breathing could allow identifying anomalies in the rhythm and waveform to be correlated with several pathologic disorders of respiratory and cardiovascular systems. A wireless sensor based on a flexible kapton substrate, suitable to be stuck over the face skin like a plaster and provided with a graphene-oxide (GO) electrode, is here proposed for application to the monitoring of the moisture emitted during inhalations and exhalations. The GO-based electrode increases its DC resistance when exposed to humidity with a sensitivity of 60 Ohm/RH. The device is compatible with the Radiofrequency Identification (RFID) standard in the UHF band. When used in battery-less mode it can be read up to 60 cm. The RFID sensor has been successfully experimented in a measurement campaign involving ten volunteers asked to reproduce a set of predefined normal and pathological breaths. The resulting resistance traces permit to well clusterize the breath patterns with respect to the respiration rate (extracted by an FFT) and to the average peak variation of the sensor’s resistance with an accuracy close to 90%.
cavity A Passive Wireless Sensor Network for the Temperature Mapping Inside a Shielded Coaxial Enclosure

S. Lopez-Soriano, I.P. Spassovsky, J. Parron, and G. Marrocco, IEEE Journal of Radio Frequency Identification, to appear

This contribution addresses the electromagnetic feasibility of the wireless temperature monitoring inside a coaxial cavity resembling a portion of a high-power high- frequency Cyclotron Auto-Resonance Maser (CARM) for plasma heating in the new generation of DEMO TOKAMAK machines. The scenario is investigated as a potential communication channel for a UHF RFID sensor network where cavity probes are used to both excite the coaxial cavity and to collect the temperature data scattered back by sensor antennas. By using a theoretical near-field analysis of a simplified model of the cavity and of the reader/sensor devices it is demonstrated that a two-probes architecture is suitable to interact with more than N=16 equally spaced RFID temperature sensors (having power sensitivity of -8.3dBmW) over the surface of a 0.5 m tube by using less than 20dBmW power emitted by the reader. The theoretical results are corroborated by experimental data with a mock-up of the cavity and realistic prototypes of miniaturized RFID radio- sensors and excitation probes.
mesh Inkjet-printed RFID-Skins for the Detection of Surface Defects

S. Nappi, G. Marrocco, URSI AT-RASC, Gran Canaria, June 2018

Hydrogel-based smart wound dressings that combine the traditional favourable properties of hydrogels as skin care materials with sensing functions of relevant biological parameters for the remote monitoring of wound healing are under development. In particular, lightweight, ultra-high frequency radiofrequency identification (UHF RFID) sensor are adjoined to xyloglucan-poly(vinyl alcohol) hydrogel films to battery-less monitor moisture level of the bandage in contact with the skin, as well as wireless transmit the measured data to an off-body reader. This study investigates the swelling behavior of the hydrogels in contact with simulated biological fluids, and the modification of their morphology, mechanical properties, and dielectric properties in a wide range of frequencies (100-106 Hz and 108-1011Hz). The films absorb simulated body fluids up to approximately four times their initial weight, without losing their integrity but undergoing significant microstructural changes. We observed relevant linear increases of electric conductivity and permittivity with the swelling degree, with an abrupt change of slope that is related to the network rearrangements occurring upon swelling.

Development and Characterization of Xyloglucan-poly(vinyl alchohol) Hydrogel Membrane for Wireless Smart-wound Dressing

A. Ajovalasit, M. C. Caccami, S. Amendola, M. A. Sabatino, G. Alotta, M. Zingales, D. Giacomazza, C. Occhiuzi, G. Marrocco, C. Dispenza, European Polymer Journal, Elseview, to appear

The aging of polymer-based objects (tires, cable harness, paints, gaskets) may appear as the formation of surface defects like cracks and scratches. An early detection of such signs may support the Predictive Maintenance of critical polymeric devices before the occurrence of a severe damage. Inkjet printed Space Filling Curves (SFC) are here proposed as an artificial electric skin, suitable to be integrated with an RFID tag, at the purpose to detect and remotely transmit the presence of small aging signs of a surface. Thanks to the particular properties of the Gosper SFC, the size and space resolution of the skin can be easily controlled by few parameters. The idea is corroborated by preliminary experimentations with low-cost inkjet printed traces that easily enable to monitor the presence of a defect from a distance of 10 m and more.

Electromagnetic Modeling of Self-tuning RFID Sensor Antennas in Linear and Nonlinear Regimes

M. C. Caccami and G. Marrocco, IEEE Transaction on Antennas and Propagation, Vol.66 - Early access, March 2018.

Multi-state chips for UHF Radiofrequency Identification ensure self-compensation of the variations in antenna impedance. This self-tuning capability can provide a digital information about the change in local boundary conditions within the vicinity of the tag. This feature can be exploited further for low-cost wireless sensing applications. An electromagnetic model of the tag in linear and nonlinear regimes allows prediction of analog and digital response of the device depending on the boundary conditions that cause the variation of the antenna impedance and/or gain. Additionally, the model provides estimation of the degradation in communication performance of the tag due to imperfect retuning of the chip impedance. The theoretical findings of the model are verified in sensing applications using a reference self-tuning tag. Sensing measurements of liquid compounds in linear regime and of the water-filling level of a box in nonlinear regime are demonstrated as a practical application of the proposed mathematical model.

skin inkjet
Inkjet Printing of Epidermal RFID Antennas by Self-Sintering Conductive Ink 

S. Amendola, A. Palombi, and G. Marrocco, IEEE Transaction on Microwave Theory and Technique,Vol.66, N.3, pp.1561-1569, Mar. 2018.

The recently introduced inkjet printing technology with ambient-sintering is here investigated for the fabrication of epidermal antennas suitable for Radiofrequency Identification (RFID) and Sensing. The attractive feature of this manufacturing process is the possibility to use low-cost printers without any high-temperature curing. In spite of the estimated maximum achievable conductivity of the ink (sigmaUHF = 1 x 105 S/m) in UHF-RFID band is two orders of magnitude lower than that of the bulk copper, a three-fold printing process provides the same on-skin radiating performance as manufacturing technologies using bulk conductors. Experiments demonstrate that the epidermal antennas printed on PET substrate are insensitive to moderate mechanical stress, like the natural bending occurring over the human body, and to the possible exposure to body fluids (e.g. sweat). Moreover, the electromagnetic response remains stable over the time when the printed layouts are coated with biocompatible membranes.


M. C. Caccami, M. Y. S. Mulla, C. Di Natale, and G. Marrocco, IET Microwaves, Antennas & Propagation, 22 Jan. 2018.

The monitoring of the breathing dynamic characteristics, including the presence of biomarkers in exhaled breath, is of growing interest in noninvasive diagnosis of diseases. We describe a wearable radiofrequency identification (RFID) device hosting a flexible antenna suitable for integration into a facemask and a sensor made of graphene oxide sensitive to the humidity variations. The resulting sensor tag was characterized in reference conditions while its communication performance was estimated by electromagnetic simulations as well as measurements over a simplified model of the human head. Finally, the whole system was tested on a volunteer and was experimentally demonstrated to be capable of detecting the inhalation/exhalation cycles and abnormal patterns of respiration like the apnea by measuring the changes in graphene oxide resistance.

tagcopter Ubiquitous Flying Sensor Antennas: Radiofrequency Identification Meets Micro Drones

M. Longhi and G. Marrocco, IEEE RFID Journal, Vol.1, N.4, pp. 291-299, Dec. 2017

Tag-Copter is an architecture of dynamic and selfrelocating sensor devices originating from the synergy between sensor-oriented Radiofrequency Identification (RFID) and the emerging Micro Air Vehicles (MAV) technology. Tag-copters integrate a low-cost nano multi-copter with a miniaturized RFID data-logger antenna for the ubiquitous and cooperative monitoring of indoor volumes as well as of harsh environments. This concept is preliminary exploited by means of a theoretical formulation to derive the upper-bound performance of a flying “winged sensor”. The analysis addresses the sensing accuracy versus the flight speed and the reliability of the on-the-flight data exchange with a fixed base-station through backscattering modulation. A first working 16 g prototype, capable of temperature measurement and storage, is experimented in a controlled setup to corroborate theoretical and experimental findings. The same device is then applied in realistic conditions concerning the temperature mapping within indoor environments. Preliminary results demonstrate that the maximum temperature measurement error is of the order of 1 °C along flight trajectories of 30 m. Finally, most of the data stored within the datalogger memory can be correctly uploaded by a flying tag-copter toward a fixed reader provided that the copter flies at approximatively 1-1.5m from it.

A Tightly Integrated Multilayer BatteryAntenna for RFID Epidermal Applications

M. C. Caccami, M. P. Hogan, M. Alfredsson, G. Marrocco and J. C. Batchelor, Transactions on Antennas and Propagation, November 2017.

For the acceptance of bio-integrated devices in daily life, radio-systems must be developed that are minimally invasive to the skin, and they must have ultra-low profile local power sources to support data-logging functionality without compromising shape-conformability. This contribution proposes a tightly integrated multilayer battery-antenna system (𝟔𝟓    × 𝟐𝟑    𝒎𝒎𝟐) that is ultra-thin (just 𝟐𝟎𝟎    𝝁𝒎), flexible, and lighter than 𝟏    𝒈, making it suitable for epidermal applications. The negative electrode (anode) current collector of the battery is a Radiofrequency Identification (RFID) tag antenna coated by a conductive polymer (Pedot:PSS) working as anode material. Since the battery is a dynamic device, subjected to discharging, the antenna design must include the variable dielectric properties of the conductive polymer that are here first characterized in the UHF band for real charge/discharge battery conditions. The communication performance of the prototype composite device is hence evaluated through the measurement of the realized gain of the tag antenna (-19.6 dBi at 870 MHz) when it is placed directly onto a volunteer's forearm.  The read range of 1.3 - 3 m is suitable for occasional data download from the epidermal data-logger when the user comes close to a reader-equipped gate.

G. Casati, M. Longhi, D. Latini, F. Carbone, S. Amendola, F. Del Frate, G. Schiavon and G. Marrocco, IEEE Journal of Radio Frequency Identification, Vol. 1, N.2, pp. 155-162, Jun. 2017

The combined use of Unmanned Aerial Vehicles and Radiofrequency Identification devices is an emerging topic of the environmental monitoring, which combines the versatility of multi-copter airframes with the potentiality of low-cost wireless sensors. This paper introduces some performance metrics suitable to quantify the capability of an RFIDrone to scan a surface equipped with radio-sensors. By using simple propagation mod- els, an optimal drone-surface distance is mathematically derived at the purpose to maximize the electromagnetic footprint for the specific choice of system parameters, such as the sensor type and position, the reader sensitivity, the ground reflectivity, the radi- ated power and the flight velocity. Theoretical achievements and some preliminary experimentations indicate that omnidirectional antennas are preferred for the drone so that 9-12m footprints could be achieved with state-of-the-art readers and battery-less or battery-assisted RFID sensors, provided that the UAV flights at 3-5 m from the surface to be monitored. In this condition, the hit-rate of arrays of tags is better than 90% for a flying speed less than 1.8 Km/h. The read performance is instead sensibly degraded by the presence of multi path in case of sensors spaced out the surface.

Reliability of a Re-usable Wireless Epidermal Temperature Sensor in Real Conditions

C. Miozzi, S. Amendola, A. Bergamini, and G. Marrocco, 14th International Conference on Wearable and Implantable Body Sensor Networks (BSN 2017), Eindhoven (The Netherlands), 9-12 May 2017.

Body temperature is among most important biometric indicators that are normally checked in both domestic and hospital environments. The way to collect such parameter could be dramatically improved thanks to the Epidermal Electronics technology enabling plaster-like devices suitable to on-skin temperature sensing and capable of wireless communication with an electromagnetic reading module. The practical applicability of an eco-friendly battery-less epidermal thermometer, compatible with the UHF RFID standard, is here discussed by the help of experimentation with some volunteers. Comfortable reading procedures can be applied for both the operator and the patient. Experiments revealed a non negligible sensitivity of the temperature measurement versus the mutual distance between the reader and the sensor, that must be removed by a proper threshold filtering. Finally, the analysis of the sensor response for different placement position over the body, demonstrates that the axilla and chest loci provide only 0.6°C deviation from a reference tympanic measurement and are well accepted by the user which does not complain about the presence of the sensor.

Finger-Augmented RFID System to Restore Peripheral Thermal Feeling

V. Di Cecco, S. Amendola, P. P. Valentini, and G. Marrocco,  11th Annual IEEE International Conference on RFID, 9-11 May 2017, Phoenix, Az.

Finger-Augmented Devices (FAD) identify a particular wearable technology suitable to turn the human fingers into enhanced sensing surfaces for advanced human-computer interfaces. The feasibility of a full on-body UHF RFID-based FAD is here investigated for the first time. The system is aimed at providing impaired people suffering from a lack of thermal feeling, due to pathological disorders, with a realtime feedback of the temperature sensed by the fingertips. The considered RFID-FAD comprises an epidermal tag suitable to conformal application over the fingertip and an interrogation wrist patch antenna. The electromagnetic challenge concerns the possibility to establish a robust RFID link when both the reader antenna and the passive fingertip tag are attached onto the lossy human skin. The occurring near-field interaction is modeled by a two-port system and experimentally tested by means of a 3D hand mockup made by additive manufacturing. Simulations and measurement permitted to derive the upper-bound performance and to estimate the required power budget. The idea is finally demonstrated with a proof of concept in a realistic application.


Wireless Monitoring of Breath by means of a Graphene Oxide-based Radiofrequency Identification Wearable Sensor

M. C. Caccami, M. Y. S. Mulla, C. Di Natale and G. Marrocco,  11th European Conference on Antennas and Propagation, 19-24 March 2017, Paris, France.

The monitoring of the breathing dynamic charac- teristics, including the presence of biomarkers in exhaled breath, is of growing interest in noninvasive diagnosis of diseases. We describe a wearable radiofrequency identification (RFID) device hosting a flexible antenna suitable for integration into a facemask and a sensor made of graphene oxide sensitive to the humidity variations. The so obtained wearable wireless sensor was characterized in reference conditions and was then experimentally demonstrated to be capable of detecting the inhalation/exhalation cycles and abnormal patterns of respiration like the apnea by measuring the changes in graphene oxide resistance.


Optimal Performance of Epidermal Antennas for UHF Radio Frequency Identification and Sensing

S. Amendola and G. Marrocco,  IEEE Transactions on Antennas and Propagation, vol. 65, no. 2, pp. 473-481, February 2017.

Skin-mounted electronics is the new frontier for unobtrusive body-centric monitoring systems. In designing the wireless devices to be placed in direct contact with the human skin, the presence of the lossy body cannot be ignored because of strong electromagnetic interactions. In this paper, the performance of epidermal antennas, for application to radio frequency identification (RFID) links in the UHF band, was investigated by means of numerical simulations and laboratory tests on fabricated prototypes. The analysis demonstrates the existence of an optimal size of the antennas (from 3 to 6 cm for loops and from 6 to 15 cm for dipoles) and of upper bounds in the achievable radiation gain (less than −10 dB in the case of 0.5 mm thick application substrates) as a consequence of the balance between the two opposing mechanisms of radiation and loss. This behavior, which is controlled by the hosting medium, does not depend on the antenna shape, even if the loop layout permits considerably minimizing the device size. Even the conductivity of the antenna trace plays only a second-order role; low-cost inkjet printable paints with conductivity higher than  10^{4} S/m are suitable to provide radiation performance comparable with the performance of copper-made antennas. Starting from the investigation of the above cited physical phenomena, including the effect of common classes of suitable substrate membranes, guidelines are finally derived for the optimal design of real RFID epidermal antennas.


Design, Calibration and Experimentation of an Epidermal RFID Sensor for Remote Temperature Monitoring

S. Amendola, G. Bovesecchi, A. Palombi, P. Coppa, and G. Marrocco, IEEE Sensors Journal, vol. 16, no. 19, pp. 7250-7257, October 1, 2016.

An epidermal RFID sensor consists of a flexible antenna provided with a radiofrequency identification and sensing microchip directly stuck over the human skin by means of a submillimeter bio-compatible membrane. A compact-size epidermal RFID thermometer is here proposed and extensively experimented concerning its electromagnetic and thermal performance in case of battery-less and battery-assisted configurations. The antenna element embeds a mechanism for a post-manufacturing frequency retuning in order to adapt its response to the specific placement over the body. When attached over the skin the sensor is readable from up to 0.7 m in battery-less mode and 2.3 m in battery-assisted mode. A calibration procedure improved the accuracy of the IC sensor down to 0.18°C. The time constant evaluated by the first-order response of the IC to impulse heating (photo-flash) resulted in 4.3 s. The epidermal wireless thermometer was experimented in both supervised applications (manual reading) and in un-supervised architectures where users were continuously monitored by a fixed remote antenna or during the crossing of a surveillance gate. In all the considered cases, the reliability of the interrogation link was experimentally quantified and resulted robust for health monitoring applications in clinical and domestic settings and even for the automatic detection of anomalous temperature peaks of people walking within airports and at country border crossing.

Constrained Pole-Zero Synthesis of Phase-Oriented RFID Sensor Antennas

S. Caizzone, E. DiGiampaolo and G. Marrocco, IEEE Transactions on Antennas and Propagation, vol. 64, no. 2, pp. 496-503, Feb. 2016.

Passive sensing by means of radiofrequency identification has been extensively explored for various applications, such as gas detection, temperature change, and deformation. The sensing indicator is generally based on the amplitude and phase of the backscattered field. However, a degradation of the communication performance must be usually accepted for achieving the sensing capability. This work introduces a design method suitable for phase-based RFID sensors that permits to shape the phase response while preserving the impedance matching between the antenna and the microchip. The RFID sensor is modeled as a two-ports scatterer comprising a lumped sensor at one of the ports and an RFID chip at the other port. A pole-zero representation of the electromagnetic interaction between the reader and the RFID sensor allows to introduce a constrained design of the antenna with a full control on the sensor dynamic range and on the communication performance. The proposed method is numerically and experimentally validated by means of a pair of strongly coupled dipoles connected to a voltage-controlled varactor emulating a dynamic sensor response.

Precision and Accuracy in UHF-RFID Power Measurements for Passive Sensing

Occhiuzzi, C.; Marrocco, G., IEEE Sensors Journal, vol. 16, no. 9, pp. 3091-3098, 2016.

In spite of analog RFID sensors are gaining increasing attention from Academic and Industrial domains, their true applicability in the real world is still in question since it is not clear whether and in which conditions the variation of the measured signals related to the sensing activity may be distinguished from the measurement uncertainties. The RFID platform for analog sensing, namely with no dedicated sensing electronics, is here characterized in term of precision and accuracy with reference to the arrangement and the reproducibility of the setup. Numerical analysis and laboratory experimentations demonstrated that the precision of power metrics measurement is twice the resolution of low-cost readers and that the uncertainty on the distance and the alignment may play a major role on the data accuracy. The environment-independent indicator, like the Analog Identifier, revealed once again to be a very stable and robust metric. In overall, the obtained results suggest that analog RFID devices can be used as indicative sensing platform to identify a few levels of the phenomenon under observation. The sensing granularity can be improved by using low-power ICs while classification algorithms could be applied to increase the robustness of the detection.

Close Integration of a UHF-RFID Transponder into a Limb Prosthesis for Tracking and Sensing 

R. Lodato
and G. Marrocco, IEEE Sensors Journal, vol. 16, no. 6, March 2016.

The technology of structural radio systems that is well assessed in the avionic and naval communications is here applied to obtain antenna functionality out of a limb prosthesis with minimal changes to the device, in specific, an orthopedic nail. A microchip transponder based on the ultrahigh frequency- radio-frequency identification (RFID) communication standard is connected to the nail by means of a central notch forming a towel-bar-like antenna. The resulting device, called prosthetic structural tag, is such to preserve the mechanical continuity of the original nail, but it is also capable of energy harvesting and RFID. The electrical and geometrical control parameters for impedance tuning were identified using computer simulation and laboratory tests. The radiation performance is mostly dependent on the geometry of the notch, while it is rather unaffected by the length of the nail, so that the proposed layout may also be applied to different kinds of prosthesis. The experimented read distance at 870–960 MHz was more than 35-cm far from the limb surface. The augmented smart prosthesis is, hence, suitable to be monitored using an external non-contacting antenna for application to tracking and, in the near future, to monitor the prosthesis health status.

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Performance of Epidermal RFID Dual-loop Tag and On-skin Retuning

S. Amendola, S. Milici, G. Marrocco, IEEE Transactions on Antennas and Propagation, vol. 63, no. 8, August 2015

Originally introduced by the material science community, the epidermal electronics is now collecting interest also among antenna engineers for the potentiality to achieve thin and flexible sensing transponders that are suitable to application over the epidermis. Unlike conventional wearable antennas, which are generally decoupled by the lossy human body by means of spacers or shielding sheets, epidermal tags need to be placed at a very close touch with the skin thus providing poor communication capabilities. This paper investigates, by means of a detailed numerical and experimental study, the performance of an epidermal dual-loop tag for UHF radiofrequency identification (RFID) depending on the specific placement over different parts of the human body and for a variety of volunteers. An on-body tuning mechanism is also introduced and demonstrated in real applications at the purpose to improve the tag response and hence to enable the use of a same tag layout for all the UHF-RFID bands and for several placement loci.

S. Amendola, L. Bianchi, G. Marrocco, IEEE Antennas and Propagation Magazine, vol. 57, no. 3, pp. 23-37, June 2015

Movement detection of human body segments is a fertile research topic in Human-Computer interaction, as well as in medical and entertainment applications. In spite of most of the current methods to track motion are based on opto-electronic systems and wearable inertial sensors, promising solutions could spring from the application of the passive Radio Frequency Identification (RFID) technology. When the human body’s limbs move within an electromagnetic field radiated by an interrogating antenna, a movement-dependent modulation of the backscattered field is sensed by the remote receiver. The collected signals, pro- perly conditioned by wearable electromagnetic markers (tags), may therefore carry intrinsic information about the human motion. This paper investigates the potentiality of the synergy between Electromagnetics and Machine Learning technologies at the pur- pose to classify arms and legs gestures by using only passive and sensor-less transponders. The electromagnetic signals, backscatte- red from the tags during gestures, are collected by a fixed reader antenna and then processed by the Support Vector Machine (SVM) algorithm at the purpose to recognize both periodic limbs movements as well as to classify more complex random motion patterns. Experimental sessions demonstrated a classification accuracy higher than 80-90% that is fully comparable with that of more complex systems involving active wearable transceivers. The results further indicate that the achievable bit-rate is 48 bits/minute suggesting that the platform could be used to input coded controls to a gesture-oriented user interface.

Phase-oriented Sensing by means of Loaded UHF RFID Tags

Caccami M.C., Manzari S., Marrocco G., IEEE Transactions on Antennas and Propagation, vol. 63, no. 10, pp.4512-4520, October 2015

Radio Frequency Identification (RFID) tags are currently evolving from an augmented version of barcodes to passive and distributed sensors in the emerging Internet of Things. Most of the RFID sensing devices that have been experienced till now are based on power metrics. The change in the environment is converted into a variation of the antenna performance remotely sensed by a reader through a modulation of turn-on or backscattered power. This paper investigates a new sensing paradigm derived from the measurement of the phase of the electromagnetic signals that are backscattered from the tag in the UHF-RFID band. The main goal is to introduce a model of the phase response of antennas that are loaded by lumped sensitive materials. General properties, data-processing issues, the achievable dynamic ranges, sensitivities, and the measurement reproducibility of phase-oriented sensing are investigated by means of both numerical analysis and experimentations concerning an RFID humidity sensor as case study.

RFID & IoT: a Synergic Pair

S. Amendola, M. C. Caccami, A. Caponi, L. Catarinucci, V. Cardellini, E. Di Giampaolo, S. Manzari, F. Martinelli, S. Milici, C. Occhiuzzi, and G. Marrocco, IEEE RFID Virtual Journal, N.8, March 2015

Internet Of Things (IoT) is driven by a combination of sensors and actuators, connectivity, people and processes. The interactions among these entities are creating new types of applications and services.
IoT will provide a dynamic global network infrastructure with self-configuring capabilities where physical and virtual “Things” have both unique identities and physical attributes and are integrated into the information network in a fully transparent way for a final user. In the framework of Internet of things, an entity can be a farm animal with a biochip transponder for identification and tracking, an historical monument protected by a structural-health monitoring-network, a person with an implanted smart prosthesis, a car with built-in sensors or any other natural or man-made object which can be provided with an IP address and with the capability to exchange data over a network. So far, the Internet of Things has been mostly associated with machine-to-machine (M2M) communication in manufacturing and power, oil and gas utilities, but many other implementations are currently being investigated and even experimented.


Epidermal RFID Passive Sensor for Body Temperature Measurements

S. Milici, S. Amendola, A. Bianco and G. Marrocco, 2014 IEEE RFID Technology and Applications Conference (RFID-TA)

Real-time and continuous wireless measurement of human body temperature could enable a better control of many pathologies such as the wounds infection after surgery and the evolution of epidemics involving fever rush, as well as the monitor of athletic activities. This paper describes an RFID passive UHF epidermal sensor suitable to be directly attached onto the human skin by means of a bio-compatible transpiring Poli(
ε-caprolacton) (PCL) membrane. The antenna elements provide a broad matching band and even a post-fabrication tuning mechanism to better manage the specific placement over the body. The temperature is directly measured by the EM4325 microchip, also providing RFID communication capabilities. The epidermal sensor, that can be read up to 35 cm in case of 0.5 W EIRP emitted by the reader, has been moreover thermally calibrated versus a thermocouple and then applied to the measurement of human body temperature in both static and dynamic conditions with an accuracy of about 0.25°C with respect to reference measurements.

A Passive Temperature Radio-Sensor for Concrete Maturation Monitoring

S. Manzari, T. Musa, M. Randazzo, Z. Rinaldi, A. Meda and G. Marrocco, 2014 IEEE RFID Technology and Applications Conference (RFID-TA)

A planar “T” like passive UHF RFID temperature sensor is here proposed for application inside the fresh concrete at the purpose to hydration monitoring during the curing procedure into caissons. Since the concrete’s electromagnetic parameters significantly change along with the drying process, the antenna modeling and design consider both the electromagnetic and the chemical phenomena. The described tag layout is such to separate, by means of a two-conductor transmission line, the sensing device, e.g. a specialized RFID IC placed up to 15cm deep into the concrete, from the scavenging element, placed instead outside the concrete. Computer simulation and then extensive laboratory experimentation in real conditions demonstrated that, despite of the low sensitivity of the IC and the high losses of concrete, the proposed RFID sensor tag provides reasonable communication performance in passive mode with read ranges up to 2 meters, and fast and reliable temperature sensing capabilities that look comparable with that of more invasive and costly wired measurement systems.

Modeling and Applications of a Chemical-Loaded UHF RFID Sensing Antenna with Tuning Capability

S. Manzari, G. Marrocco, IEEE Trans. Antennas and Propagat., Vol. 62, N.1, pp 94-101, Jan. 2014

A key-issue of the wireless gas sensing by radio frequency identification is the capability to control the sensor's response while minimizing the amount of chemical interactive materials (CIM) required to dope the tag antenna. An open-circuit shielded slot-line layout is proposed as a general purpose tunable radio frequency identification (RFID) radiator, suitable to host small amounts of CIM. It operates both as a very efficient passive sensor and as a tool to estimate the electromagnetic equivalent parameters of the CIM during the gas exposure. A hybrid distributed-lumped model permits to separate the CIM's contribution from the antenna's response and, in addition, it provides a simple tool to shape the calibration curve relating RFID power signals to the physical changes of the environment. The tag layout and the method are applied to the UHF characterization of the conductive polymer Pedot:PSS and to the optimization of high-performance humidity sensor capable of a three-times higher sensitivity than those achieved by the current state of the art RFID devices.

C. Occhiuzzi, C. Vallese, S. Amendola, S. Manzari, G. MarroccoProcedia Computer Science, Vol.32, pp.190.197, 2014

An Ambient Intelligence platform, NIGHTCare, for remote monitoring and control of overnight living environment is here proposed. The platform, entirely based on RFID passive technology is able to recognize nocturnal behaviors and activities, generates automatic alarms in case of anomalous or pathological events and support diagnostics. The results of a complete test in real scenario are presented, together with a numerical assessment of electromagnetic safety issues.

Wireless Crack Monitoring by Stationary Phase Measurements from Coupled RFID Tags

S. Caizzone, E. DiGiampaolo, G. Marrocco, Trans. Antennas Propagat., Vol.62, N12, pp.6412-6419, Dec. 2014

The possibility to wirelessly monitor the state and the evolution of cracks is of increasing interest in emerging structural health monitoring systems. A simple and effective measurement method considers the placement of two passive radio frequency identification (RFID) antennas on top of the crack, so that the crack's evolution will produce a change of the inter-antenna coupling and in turn of the phase of the backscattered field. An ad-hoc design technique, based onto the coupled-modes physics, permits to maximize the sensor's sensitivity avoiding, or at least mitigating, the read range reduction during the evolution of the displacement that is instead typical of amplitude-oriented RFID displacement sensors. The proposed idea is demonstrated by numerical and experimental examples showing the possibility of sub-millimeter resolution with low-cost devices.

Sub-millimeter displacement sensing by Passive UHF RFID Antennas

C. Paggi, C. Occhiuzzi, G. Marrocco, IEEE Trans. Antennas and Propagat., Vol. 62, N.2, pp.905-912, Feb. 2014

A slotted patch is transformed into a wireless passive UHF-RFID sensor of uni-dimensional displacements by introducing a mechanic-electromagnetic modulation capable to convert sub-millimeter deformations into changes of the antenna’s response, remotely detectable. A design methodology allows to obtain the desired sensitivity and dynamic range in a fully controllable way. The sensor and the methodology are discussed through the help of preliminary laboratory experimentations on a concrete brick, showing the possibility to achieve resolutions better than 0.1 mm with low cost readers.

RFID Technology for IoT-based Personal Healthcare in SmartSpaces

S. Amendola, R. Lodato, S. Manzari, C. Occhiuzzi, G. Marrocco, IEEE Internet of Things Journal, Vol.1, N.2, pp. , 144.152, April 2014

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 user's 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 user's 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.

R. Lodato, V. Lopresto, G. Marrocco, R. Pinto, IEEE Transactions on Antennas and Propagation, Vol.62, No 10, Oct. 2014

Radio frequency identification (RFID) in the UHF band has been recently proposed as enabling technology to develop implanted radio-sensors to be integrated into orthopedic prosthesis because of the power autonomy and standardized communication protocols. This paper investigates the feasibility of direct and forward links for UHF-RFID (860-960 MHz) tags implanted into human limbs, that are interrogated by a noncontacting reader's antenna, with the purpose to label and, in a near future, to collect data about the health status of an implanted orthopedic prosthesis. Performance gain indicators of the through-the-body RFID channel are estimated by electromagnetic simulations over an anthropomorphic phantom as well as by means of experimentation with a real RFID communication link involving a simplified in vitro setup. The achieved results suggest that, by exploiting the current potentialities of RFID technology, and for the specific tag (loop antenna) and reader antenna (SPIFA) herein considered, a stable communication link with tags implanted inside limbs might be already feasible up to 10-35 cm from the body in full compliance with the constrains over electromagnetic exposure. In the particular case of implanted tag into an elbow, the estimated power margin in the direct and inverse links could be even suitable to set up sensing-oriented systems based onto turn-on and backscattered power modulation.

S. Manzari, A. Catini, G. Pomarico, C. Di Natale, G. Marrocco, IEEE Sensor Journal, Vol. 14, N.10, pp.3616-3623, 2014

Battery-less ultrahigh frequency (UHF) radio frequency identification (RFID) tags coated by proper sensitive layers have been recently demonstrated capable to play as low-cost sensors of some volatile compounds. The issue of cross-sensitivity and the possibility to develop an array of differently coated sensors are, however, still completely open. This paper investigates, through an experimental campaign involving a general-purpose sensor-antenna transducer, the potentiality of functionalized tags in the UHF RFID band to sense a multiplicity of volatile compounds, as well as the cross-sensitivity effects of different coatings in array configuration. Four effective materials, such as Pedot:PSS, doped PSS, SWCNT, and PDAC, revealed a remarkable sensitivity to ammonia, ethanol, octane, and water. Wireless sensing may be hence performed by narrowband processing of the power response of the RFID tags as well as by the broadband extraction of features related to the resonance shift. It was finally observed how the inter-antenna coupling may affect the sensor capability of an array of UHF tags in term of increased cross-sensitivity.


Constrained-Design of Passive UHF RFID Sensor Antennas

C. Occhiuzzi, G. Marrocco, IEEE Trans. Antennas and Propagat., Vol.61, N.6, pp.2972-2980, June 2013

Passive UHF RFID tags may be used, beside labeling, to remotely observe the physical/chemical change of the tagged object, through modulation of their impedance and gain, thus acting as sensor antennas. The design of this new class of devices can be mastered by fully understanding the relationship between communication and sensing with the purpose to balance the maximization of the dynamic range of the response with the stability of the read distance. A new kind of communication/sensing nomogram permits to display both behaviors in a unitary way and to predict their physical limits, as well as to formalize a multi-parameter general-purpose optimization methodology. The procedure is demonstrated by application to the design of a strain-gauge tag and of a level-detector wireless sensor.

Passive UHF RFID Antennas for Sensing Applications: Principles, Methods and Classifications

C. Occhiuzzi, S. Caizzone, G. Marrocco, IEEE Antennas and Propagat. Magaz., Vol.44, N.6, pp.14-34, Dec, 2013

UHF passive radio-frequency identification technology is rapidly evolving from simple labeling of things to wireless pervasive sensing. A remarkable number of scientific papers demonstrate that objects in principle can have their physical properties be remotely tracked and monitored all along their life cycle. The key background is a new paradigm of antenna design that merges together the conventional communication issues with more-specific requirements about sensitivity to time-varying boundary conditions. This paper presents a unified review of the state of the art of the tag-as-sensor problem. Particular care is taken to formalize the measurement indicators and the communication and sensing tradeoff, with the purpose to provide a first knowledge base for facing a large variety of emerging sensing applications.


Miniaturized wearable UHF-RFID tag with tuning capability

S. Manzari, S. Pettinari, G. Marrocco, Electronics Letters, VoL. 48, N. 21, p.1325–1326

By carving a ‘square-smile’ slot profile over a folded patch, a miniaturised UHF-RFID tag is obtained, having a convenient two-step tuning mechanism (coarse and fine). This is useful to adapt the same tag to European and US frequencies and to make on-site corrections. The antenna is half the size of a credit card and can be read up to 5m when attached onto the body. The flexible and lightweight EPDM foam substrate makes the tag suited to be integrated in badges, wallets, pockets, plasters, wristbands and various garments.

Performance Analysis of Pure Paraffin Wax as RFID tag Substrate

S. Manzari, A.A. Babar, L. Ukkonen, A. Z Elsherbeni, G. Marrocco, L.Sydanheimo, Microwave and Optical ans Technology Letters, vol.54, N.2, pp.442-446, Feb. 2012

The article presents an investigation of the performance of the Paraplast, a kind of pure paraffin wax, used as a substrate of RFID tag antennas operating at UHF RFID band. To achieve this purpose, two similar RFID tag antennas with same dimensions have been simulated, fabricated and tested. These include a simple dipole tag on a Rogers RT/Duroid 5880 substrate and on pure paraffin substrate. Because of the relatively close dielectric constant values, paraffin substrate is compared with Duroid RT5880. Paraffin wax can be considered as a low cost and low loss substrate. The main purpose in the future will be using paraffin as a passive temperature sensor, by exploiting the changes in molecular structure, volume and dielectric properties with temperature, especially near its melting point.

Feasibility of Body-centric Systems by Using passive textile RFID tags

S. Manzari, C, Occhiuzzi, G. Marrocco, IEEE Antennas and Propagation Magazine, Vol.54, N.9, pp 2851-2858, 2012

Recent progresses in the design of wearable RFID-tag antennas stimulate the idea of passive body-centric systems, wherein the required power to drive the wearable tags is directly scavenged from the interrogation signal emitted by the reader unit. While active body-centric links have been extensively investigated, the feasibility of passive systems is still questionable, due to the poor sensitivity of the tags and due to the modest reading distances. This paper describes a systematic measurement campaign involving low-profi le wearable textile tags in the UHF RFID band. It was demonstrated that both on-body and off-body links are affordable, with a power budget fully compliant with the available technology and the safety standards. The experiments permitted identifying the most-effi cient tag placements, and proposing some quantitative and general guidelines useful to characterize and design this kind of new system.

Design of Implanted RFID Tags for Passive Sensing of Human Body: the STENTag

C. Occhiuzzi, G. Contri, G. Marrocco, IEEE Trans. Antennas and Propagat. Vol.60, N.7, pp.3146-3154, 2012

Numerical processing of passive UHF-RFID tags' response may provide physical insight about the hosting object or about the nearby environment. This idea is here extended to implanted antennas with the purpose to sense the evolution of some human physiological and pathological process involving a local change of effective permittivity inside the body. The goal is to understand how master the design of this class of devices taking into account both communication and sensing capabilities. An ad hoc design methodology is here presented and discussed by means of a realistic medical case concerning the modification of an endo-vascular device to achieve a STENTag able to sense the state of the vessel wherein it has been implanted.

Humidity Sensing by Polymer-loaded UHF RFID Antennas

S. Manzari, C. Occhiuzzi, S. Nawale, A. Catini, C. Di Natale, and G. Marrocco, IEEE Sensors Journal, Vol.12, N.9, pp. 2851-2858, 2012

Passive ultra high-frequency radio frequency identification tags, besides item labeling, are also able to exploit capability to sense the physical state of the tagged object as well as of the surrounding environment. Here, a new family of polymer-doped tags are proposed and fully characterized for the detection of ambient humidity. A sensitive chemical species based on PEDOT:PSS is used to load a shaped slot, carved into a foldedlike patch tag. The communication and sensing capabilities of the resulting radio-sensor are investigated by means of simulation and measurements that show how to control and balance above opposite requirements by a proper deposition of the sensitive material. The device could have interesting applications in the assessment of the air quality within living and controlled rooms, in the monitoring of the conservation state of foods, in the preservation of walls, and even in the medical field, e.g., to monitor the healing of wounds.

Electromagnetic Models for Passive Tag to Tag Communications

G. Marrocco, S. Caizzone, IEEE Trans. Antennas and Propagat. Vol.60, N.11, pp. 5381-5389, 2012

The UHF passive radio frequency identification technology generally enables an asymmetric interaction between the reader and the tag, the latter only being able to respond to the query of the reader through backscattering modulation. Very recently, some experiments put into evidence the possibility to set up a tag-to-tag communication by using a simple illuminator. The key issues and the physical limitation of such a cross-link are here investigated both theoretically and numerically by fully accounting for the mutual coupling among the tags, their radiation properties and the impedance modulation. The analysis reveals that the cross-link range may be optimized by a proper design of the tags’ input impedance and that alignment of a multiplicity of tags could be able to communicate according to a simple routing strategy.


Passive Strain-Sensor based on Meander-line Antennas

C. Occhiuzzi, C. Paggi, G. Marrocco, IEEE Trans. Antennas and Propagat. Vol.59, N.12, pp.4836-4840, Dec. 2011

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.

RFID Passive Gas Sensor Integrating Carbon Nanotubes

C. Occhiuzzi, A. Rida, G. Marrocco, M. Tentzeris, IEEE Microwave Theory Tech. , Vol.59, N.10 part 2,, pp. 2674-2684, 2011

Carbon nanotube (CNT) composites are sensitive to the presence of gases due to their high surface-to-volume ratio and hollow structure that are well suited for gas molecule absorption and storage. Such sensing capability is here integrated with UHF RF identification (RFID) technology to achieve passive and low-cost sensors, remotely readable. CNT film (buckypaper) is used as a localized variable resistive load integrated into a tag antenna, which becomes able to transduce the presence of hazardous gas in the environment, ammonia in this case, into a change of its electromagnetic features. The dynamic range and the hysteresis of the radio sensor are investigated by simulations, equivalent circuits, and articulated experimentations within a true RFID link, providing the proof of concept and some guidelines for tag design.

RFID Grids: Part II - Experimentations

S. Caizzone, G. Marrocco, IEEE Trans. Antennas and Propagat. Vol. 59, N.8, pp. 2896-2904, Aug. 2011

The RFID Grid is a model for generally coupled multitudes of tags including single-chip tags in close mutual proximity or a single tag with a plurality of embedded microchips. Some properties of this new entity, useful for passive Sensing and for Security, are the possibility to increase the read-range and to provide responses rather insensitive to the interrogation modalities. These recently introduced issues are here experimented for the first time with many real-world examples comprising multi-chip configurations designed for improved power scavenging and for passive sensing of things.

Multi-chip RFID Antenna Integrating Shape Memory Alloys for Detection of Thermal Thresholds

S. Caizzone, C. Occhiuzzi, G. Marrocco, IEEE Trans. Antennas and Propagat. Vol.59, N.7, pp. 2488-2494, Jul, 2011

Low-cost wireless measurement of objects' temperature is one of the greatest expectation of radiofrequency identification technology for the so many applications in cold supply-chain control and safety assessment in general. In this context, the paper proposes a dual-chip UHF tag embedding shape memory alloys (SMA) able to transform the variation of the tagged item's temperature into a permanent change of antenna radiation features. This event-driven antenna is hence able to selectively activate the embedded microchips according to the temperature above or below a given threshold. A general design methodology for the resulting two-ports tag antenna is here introduced and then applied to prototypes able to work at low (around 0°C) and high (80°C) temperatures.

RFID Grids: Part I - Electromagnetic Theory

G. Marrocco, IEEE Trans. Antennas and Propagat. Vol.59, N.3, pp. 1019-1026, March 2011

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.


Pervasive Electromagnetics: sensing paradigms by passive RFID Technology

G. Marrocco, IEEE Wireless Communications, Invited Paper, Vol.17, N.6, pp.10-17, Dec. 2010

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.

The RFID Technology for Neuroscience: feasibility of Limbs' Monitoring in Sleep Diseases

C. Occhiuzzi, G. Marrocco, IEEE Trans. Information Technology in Biomedicine, Vol.14, N.1, pp. 37-43, Jan. 2010

This contribution investigates the feasibility of the passive UHF RF identification technology for the wireless monitoring of human bodymovements in some common sleep disorders by means of passive tags equipped with inertial switches. Electromagnetic and mechanical models as well as preliminary experimentations are introduced to analyze all the significant issues concerning the required power, the tag antenna design, the read distance, and the expected biosignals collected by the interrogation device.

Hermite-Rodriguez UWB Circular Arrays

G. Marrocco, G. Galletta, IEEE Trans. Antennas and Propagat., Vol.58, N.2, pp.381-390, Feb. 2010

Pulsed circular arrays are collecting growing interest in radar applications such as automotives and indoor navigations. This contribution presents the analytic derivation of the spacetime and energy patterns of pulsed circular arrays in terms of geometrical and electrical parameters as well as of the signal distortion produced by the antennas’ response. It is shown that the field emitted by circular arrays with many elements can be represented as a summation of a practically finite set of high-order Hermite-Rodriguez waveforms, while the energy pattern is a generalized Hypergeometric Function. The angular and temporal resolutions are finally related, through handy formulas, to the array size, the input signals and to the antenna types.

Modeling design and experimentation of wearable UHF RFID sensor tag antennas

C. Occhiuzzi, S. Cippitelli, G. Marrocco, IEEE Trans. Antenna Propagat., Vol.58 N.8, pp. 2490 - 2498, 2010

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.

RFID-Network Planning by Particle Swarm Optimization

E. Di Giampaolo, F. Fornì, G. Marrocco, Aces Journal, Vol.25, N.3, pp. 263-272, March 2010

The design of an ad-hoc network of readers for a complex RFID system in large areas requires the deployment of a large number of readers due to the limited range of reader-tag communication. For passive tags the factors affecting the performance of the reader-tag communication depends on many physical and geometrical parameters. Line of sight is a constraint of the reader-tag link while scattering objects producing electromagnetic interferences affect the shape and the extension of the read-zone i.e. the region where a reader can activate a tag. This region depends not only on the emitted power and reader/tag antennas radiation patterns but also on the propagation environment. When a number of readers are planned in a network, mutual coverage of read-zones and mutual interference among readers are undesired while safety regulation constraints have to be fulfilled in the whole area. Simple and effective models of electromagnetic elements involved in the planning are developed and included in the frame of a Particle Swarm Optimization algorithm. Numerical results show the effectiveness of the method.


Estimation of UHF RFID Reading Regions in Real Environments

E. Di Giampaolo, R. Aliberti, G. Marrocco, IEEE Antennas and Propagation Magazine, Vol.51, N.6, pp. 44-57, Dec. 2009

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.


G. Marrocco, IEEE Antennas and Propagation Magazine, Vol.50, N.3 pp.147-150, June 2008

Multi-port Sensor RFIDs for Wireless Passive Sensing - Basic Theory and Early Simulations

G. Marrocco, L. Mattioni, C. Calabrese, IEEE Trans. Antennas Propagation. Vol.56, N.8, pp., Aug. 2008

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.

Meandered-slot antennas for sensor-RFID tags

G. Marrocco, C. Calabrese, IEEE Antennas and Wireless Propagation Letters. Vol.7, pp.5-8, 2008

This letter introduces a planar antenna layout suited to Sensor-RFID fabrication. The geometry is based on a meandered-slot profile on a suspended patch and permits to host sensors and electronics in a small space. The available geometrical parameters are optimized by means of a Genetic Algorithm (GA) procedure aimed to maximize the antenna realized gain. The antenna performances are discussed through examples and prototypes.

The Art of UHF RFID Antenna Design: Impedance Matching and Size Reduction Techniques

G. Marrocco, IEEE Antennas and Propagation Magazine, Vol.50, N.1, pp.66-79, Feb. 2008

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.

Naval Structural Antenna Systems for Broadband HF Communications - Part III: Experimental Evaluation on Scaled Prototypes

L. Mattioni, F. Di Lanzo, G. Marrocco, IEEE Trans. Antennas Propagation, vol.56, n.7, pp.1882-1887, Jul. 2008

We describe the design, fabrication and measurement of reduced-size prototypes of the naval structural antenna, recently proposed as a compact and multifunction solution to broadband naval communications. The original broadband HF sub-radiator, loaded by lumped impedances, is scaled down to the VHF/UHF ranges and re-designed in planar technology in order to simplify and to automate the fabrication process. Measurement on single-port and 4-port antennas, in which the central structure resembles a naval funnel and a big mast, have shown a good agreement with the simulations.

Time Domain Synthesis of Pulsed Arrays

M. Ciattaglia, G. Marrocco, IEEE Trans. Antennas Propagation, Vol.56, N.7, pp.1928-1938, Jul. 2008

Pulsed arrays are becoming popular in new ultrawideband applications to enhance the robustness of transmitted and received signals in complex environments and to identify the angle of arrival of multiple echoes. A global synthesis technique is here proposed to shape the array field in accordance to given angle-time constraints. The synthesis problem is cast as the inverse Radon transform of a desired array mask, applying the alternate projections method to include constraints over the input signals’ waveform and to improve the synthesis robustness. The unknown array currents are generated as linear combinations of Hermite–Rodriguez functions in order to achieve a simple and realizable beamforming network. The effectiveness of the method is demonstrated by many examples.


RFID antennas for the UHF remote monitoring of human subjects

G. Marrocco, IEEE Trans. Antennas Propagat., Vol.55, N.6, pp. 1862-1870, June 2007

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.

Simultaneous time-frequency modeling of ultra-wideband antennas by two-dimensional Hermite processing

G. Marrocco, M. Migliorelli, M. Ciattaglia, Progress In Electromagnetic Research, PIER, Vol. 68, pp. 317-337, 2007

This paper proposes an approximate space-time-frequency field representation for directive Ultra-wideband antennas useful to be introduced into a system-level evaluation tool. Based on the observation that the very near field collected on a plane close to the antenna exhibits a compact support, such a field is processed in the time domain by the two-dimensional Hermite transform. This approach permits to simultaneously express the antenna impulse response and the transfer function by semi-analytical formulas. The theory is demonstrated by numerical examples which highlights that good representations of complex antennas can be achieved by a small set of associate Hermite functions.

Design of a Broad-band HF Antenna for Multi-mode Naval Communications - part II: extension to VHF/UHF ranges

L. Mattioni, G. Marrocco, IEEE Antennas and Wireless Propagation Letters, Vol.2, pp.83-85, 2007

This letter proposes a broadband antenna system with omnidirectional features, operating from 2 to 440 MHz. The basic antenna structure is the bifolded monopole, recently proposed as multimode high-frequency (HF) naval antenna, which is here augmented with a top-mounted discone mainly operating in the very-high-frequency (VHF) band. A mechanical and electrical integration strategy, which can be also extended to other antenna typologies, based on the lumped impedance loading to reduce the interantenna coupling, is described.


BLADE: A Broadband Loaded Antennas DEsigner

L. Mattioni, G. Marrocco, IEEE Antennas Propagat.Magazine, Vol. 48, N.5, pp.120 - 129, 2006

This paper presents a software tool for designing loaded antennas equipped with matching networks for broadband or multiband applications. The software implements a genetic algorithm to automatically optimize the large set of parameters involved in the design procedure. The graphical interface has been designed in MATLAB® to be used together with the popular NEC solver. However, the possibility of handling reduced-port models of the antenna permits the use of any kind of numerical solver for the electromagnetic analysis. Some examples of broadband and multi-band antenna designs in a complex environment demonstrate the potential of the tool.

Investigation on antenna coupling in Pulsed Arrays

M. Ciattaglia, G. Marrocco, IEEE Trans. Antennas Propagat. vol. 54, n.3, pp.835-843, March, 2006

Pulsed arrays are becoming popular in new ultrawide-band applications to achieve long-range coverage, high capacity and to identify the angle of arrival of multiple echoes in complex environments. As in the monochromatic regime, distortion of ultrawide-band transmitted and received signals can result from the coupling between individual radiators that are in close proximity. This paper investigates the time-domain coupling in finite arrays that radiate short pulses, by introducing the concept of time-domain "active" array factor and "active" element factor. The proposed model highlights the signal-distortion phenomenology and obtains useful guidelines to reduce pulse coupling, even in dense arrays, by a proper choice of the geometrical and electrical parameters.

Naval Structural Antenna Systems for Broadband HF Communications - Part II: Design Methodology for Real Naval Platforms

G. Marrocco, L. Mattioni, V. Martorelli, IEEE Trans. Antennas Propagat. vol. 54, n.11, pp.3330 - 3337, Nov., 2006

Recently, it was shown how to make a multipurpose broadband HF antenna system out of existing naval superstructures such as the funnel or a big mast. The idea was discussed by means of canonical structures, e.g., a cylindrical body of circular or square cross-section, placed onto an infinite ground plane. This paper investigates the critical aspects concerning the extension of naval structural antenna concept to real ship platforms with the aim to define a general design methodology for impedance matching and radiation pattern control. The method is described with reference to a realistic frigate model, whose big mast is transformed into a broadband HF antenna system able to perform communications by both sea-wave and sky-wave links. It is demonstrated that, even in a real environment, the multiport strategy permits to increase the system efficiency and to moderately shape the radiation pattern in order to overcome the shadowing effect due to other large objects.

Naval structural antenna systems for broadband HF communications

G. Marrocco, L. Mattioni, IEEE Trans. Antennas Propagat. vol. 54, n.4, pp.1065 - 1073, April, 2006

This paper introduces the concept of multipurpose structural antenna system for shipborne installations. By combining properly shaped and loaded wire radiators together with an existing naval superstructure, such as the funnel or a big mast, it is possible to achieve a broadband high-frequency compact radiating system which permits handling both sea-wave and near vertical incidence sky-wave communications. When provided with a plurality of feeding points, the naval structural antenna may be used in multichannel mode, with a huge efficiency improvement over the conventional multichannel broadband systems requiring a combining network. Additionally it is shown that, when fed in monochannel mode, the structural antenna system exhibits focusing features with the possibility to achieve sectorial coverages. This paper demonstrates the advantage and limitation of this new system by carefully taking into account the interantenna coupling.


Approximate calculation of time-domain effective height for aperture antennas

M. Ciattaglia, G. Marrocco, IEEE Antennas Propagat vol.53, n.3, pp.1054-1061, Mar. 2005

The time-domain (TD) effective height is a space-time vector operator recently introduced to describe the performance of ultrawide-band antennas. Since generally obtained by measurements or intensive numerical modeling, it is represented through a large set of data not very suitable to the evaluation of the whole TD link. For the particular class of aperture-radiating antennas of separable shapes, such as slot, open-ended waveguides and horns, this paper proposes a systematic TD processing of the aperture field, involving model-based deconvolution and parameter estimation, at the purpose of an efficient calculation and a more manageable representation of the effective height. Following the idea at the base of modal near to far field transformation, as previously presented by the authors, the processing of the aperture impulse response is here addressed with a particular care to the fast varying early transient. The corresponding time-dependent Radon transforms are then approximated by semi-analytical formulas whose accuracy is discussed as for the aperture size and frequency limits. The proposed methods, which are much faster than the conventional approach, are demonstrated by some examples.

Design of a Broad-band HF Antenna for Multi-mode Naval Communications

L. Mattioni, G. Marrocco, IEEE Antennas and Wireless Propagation Letters, vol.4, pp.179-182, 2005

This paper describes a multifunction HF-loaded antenna for broadband naval communications based on both groundwave and near vertical incidence skywaves. The antenna, denoted as bifolded monopole, is designed according to a new loading strategy which avoids the use of complicated external networks. Numerical simulations and measurements on a scaled prototype have shown that interesting capabilities are obtained by using just four or five loading circuits.


Ultra-wide band modelling of transient radiation from aperture antennas

G. Marrocco, M. Ciattaglia
, IEEE Trans. Antennas Propagat. vol. 52, n.10, pp. 2341-2347, Sep. 2004

A new method for the numerical calculation of transient field radiated through aperture-type antennas (slot, open-ended waveguide, and horn) is described. The finite-difference time-domain method is applied for the near-field prediction in the close surrounding of the antenna and a proper data-fitting procedure of the aperture field, involving interpolating functions with separation of space- and time dependence, permits: 1) to calculate “off-line” the radiated field without the need to store a great amount of data; 2) to avoid, in the case of far field, the numerical evaluation of radiation integral; and 3) to obtain approximate far field formulas which are still separable with regard to space and time. The method enables a full data reusability in calculation of field pattern over a wide angular range at a same time, or of the transient response at fixed observation points.

New method for modelling and design of multi-conductor airborne antennas

G. Marrocco, P. Tognolatti, IEEE Proceed. Microwave Antennas Propagation, vol.151, pp. 181-186, Mar. 2004

A new approach is proposed, based on numerical (FDTD) and analytical (multiconductor transmission line MTL) tools, for the modelling of HF loop antennas mounted on aircraft. This method can be used to calculate the significant mutual coupling and the interaction with the body of the aircraft and also to perform fast optimisation of antenna size and position.

Time-dependent microwave radiometry for the measurement of temperature in medical applications

F. Bardati, G. Marrocco, P. Tognolatti, IEEE Trans. Microwave Theory Tech, vol.52, n.8, pp.1917-1924, Aug. 2004

Microwave radiometry has been considered for the noninvasive monitoring of internal temperature in biological bodies when the temperature is varied under the control of external sources and contacting fluid. The body temperature is modeled as a discrete-time controlled statistical process, whose estimate is cyclically updated exploiting radiometric measurements. The Kalman filter has been used, which is able, with the proper choice of parameters, to balance the temperature retrieval between a priori information and measurements. Prospective applications to medicine have been investigated for temperature monitoring within a neonatal head during a hypothermia treatment.


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

G. Marrocco, IEEE Antennas and Wireless Propagation Letters, vol.2, pp.302-305, 2003

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 into account the conductor losses. Examples are presented for application at 869 MHz with antennas of different materials and sizes.

Modal near-field to far-field transformation for FDTD modelling of aperture antennas

G. Marrocco, J. of Electromagn. Waves and Appl. vol.17, n.1, pp.79-98, Jan. 2003

This paper describes a new numerical approach for the broad-band analysis of aperture antennas which avoids the use of both ω-domain and k-domain discrete Fourier transform. The FDTD method is adopted for the near field analysis of the antenna and the aperture field is then processed by time-domain modal expansion to obtain broadband gain pattern. The new method is specified for rectangular aperture antennas and is demonstrated by means of some examples.