Backscattering UWB/UHF hybrid solutions for multi-reader multi-tag passive RFID systems

Ultra-wideband (UWB) technology is foreseen as a promising solution to overcome the limits of ultra-high frequency (UHF) techniques toward the development of green radio frequency identification (RFID) systems with low energy consumption and localization capabilities. While UWB techniques have been already employed for active tags, passive tags solutions are more appealing also due to their lower cost. With the fundamental requirement of maintaining backward compatibility in the RFID domain, we propose a hybrid UWB/UHF architecture to improve passive tag identification both in single-reader and multi-reader scenarios. We then develop two hybrid algorithms: the first one exploits the UWB signal to improve ISO/IEC 18000-6C UHF standard, while the other one exploits UWB to enhance a compressive sensing (CS) technique for tag identification in the multi-reader, multi-tag scenario. Both solutions are able to improve success rate and reading speed in the tag identification process and reduce the energy consumption. The multi-reader version of the proposed approaches is based on a cooperative scheme in order to manage reader-tag collisions and reader-reader collisions besides the typical tag-tag collisions. Furthermore, timing synchronization non-idealities are analyzed for the proposed solutions and simulation results reveal the effectiveness of the developed schemes

Ultra-wide bandwidth backscatter modulation: processing schemes and performance

Future advanced radio-frequency identification (RFID) systems are expected to provide both identification and high-definition localization of objects with improved reliability and security while maintaining low power consumption and cost. Ultrawide bandwidth (UWB) technology is a promising solution for next generation RFID systems to overcome most of the limitations of current narrow bandwidth RFID technology, such as reduced area coverage, insufficient ranging resolution for accurate localization, sensitivity to interference, and scarce multiple access capability. In this article, the UWB technology is applied to passive RFID relying on backscatter modulation. A signaling structure with clutter and interference suppression capability is proposed and analyzed. The potential performance is investigated in terms of range/data rate trade-off, clutter suppression, and multiple access capability using experimental data obtained in both the controlled and realistic environments

Co-Design Strategies for Energy-Efficient UWB and UHF Wireless Systems

This paper reviews the most recent methods, combining nonlinear harmonic-balance-based analysis with electromagnetic (EM) simulation, for optimizing, at the circuit level, modern radiative RF/microwave systems. In order to maximize the system efficiency, each subsystem must be designed layoutwise, accounting for the presence of the others, that is, accounting for its actual terminations, rather than the ideal ones (50 Ω). In this way, the twofold goal of minimizing size and losses of the system is obtained by reducing intersystem matching networks. Indeed, terminations are complex, frequency-dispersive, and variable with the signal level, if active operations are concerned, and are responsible for performance degradation if not properly optimized. This approach is nowadays necessary, given the ever increased spread of pervasively distributed RF microsystems adopting miniaturized antennas, such as radio frequency identification (RFID) or wireless sensor networks, that must be low-cost, low-profile, low-power, and must simultaneously perform localization, identification, and sensing. For the design of a transmitter and a receiver connected with the respective antennas, suitable figures of merit are considered, encompassing radiation and nonlinear performance. Recent representative low-profile realizations, adopting ultra-wideband (UWB) excitations are used to highlight the benefit of the proposed nonlinear/EM approach for next generation energy autonomous microsystem, such as UWB-RFID tags

A Novel 3-D Printed Dual-Port Rectenna for Simultaneous Energy Harvesting and Backscattering of a Passively Generated UWB Pulse

This work presents the design and characterization of a new compact rectenna system, fully three-dimensional (3-D) printed on a low-cost material, the polylactic acid (PLA). The rectenna consists of a patch-like antenna, with two orthogonal excitation ports, suitably designed to achieve both ultra-high-frequency (UHF) and ultra-wideband (UWB) cross-polarized radiation performance. The first port harvests multi-tone RF power at UHF, around 2.47 GHz (for the present case 8 equally spaced non-synchronized tones are used); the second port backscatters the intermodulation (IM) products generated by the rectifier, realizing a quasi-UWB pulse. The rectifier consists of a single-diode embedded into two linear subnetworks: one, connecting the UHF port and the diode, is co-designed to ensure dc-block and rectifier-antenna matching in the UHF band; the second one combines a high-pass filter, connecting the diode and the UWB port, to backscatter the passive pulse, and a dc path to collect the converted dc power. The 3-D etching of the low-cost substrate is optimized to obtain antenna performance comparable to those achieved with specialized RF materials. The system design is carried out by integrating full-wave and nonlinear simulations with the manifold goal of minimizing the overall footprint, ensuring UWB-mask-compatible radiated spectra and RF-to-dc conversion efficiency. A 3-D printed prototype has been realized and experimentally characterized. With a total received power of -15 dBm, equally distributed over eight tones spaced by 1 MHz, a quasi-UWB pulse power peak of about 80 nW has been demonstrated

Design and Modelling of Wireless Power Transfer and Energy Harvesting Systems

The escalation of the Internet-of-Everything topicality has motivated an increased interest in both academia and industry research for efficient solutions enabling self-sustained smart operations. From the maintenance point of view, indeed, battery-less strategies represent the most valuable way for distributed zero-power standalone electronics. With this purpose, different scavenging techniques are being adopted, gathering energy from different sources such as mechanical, solar, thermal and electromagnetic waves. Due to the wide spread of wireless communication systems, the latter technology has recently benefited a renewed interest. This Ph.D. research activity has been focused on the investigation of new efficient solutions for radiofrequency energy harvesting and wireless power transmission techniques, aiming at improving the state of the art, by also taking into account the imperative necessity of eco-friendly materials for the development of green electronics. The combination of radiofrequency energy harvesting and ultra-wideband techniques is also proposed as possible candidate for future RFID systems. These functionalities are integrated in a novel, compact and low-profile tag, whose details are provided thoroughly from both electromagnetic and nonlinear circuit viewpoints. Results validation is provided through experimental characterization. Compatibility with the environment is assured by implementation with recyclable material. This concept is then extended with the investigation of more elaborated energy scavenging architectures, including rectenna arrays. Finally, a near-field wireless power transmission system is presented on low-cost materials, therefore suitable for possible mass-market deployment

Next-generation IoT devices: sustainable eco-friendly manufacturing, energy harvesting, and wireless connectivity

This invited paper presents potential solutions for tackling some of the main underlying challenges toward developing sustainable Internet-of-things (IoT) devices with a focus on eco-friendly manufacturing, sustainable powering, and wireless connectivity for next-generation IoT devices. The diverse applications of IoT systems, such as smart cities, wearable devices, self-driving cars, and industrial automation, are driving up the number of IoT systems at an unprecedented rate. In recent years, the rapidly-increasing number of IoT devices and the diverse application-specific system requirements have resulted in a paradigm shift in manufacturing processes, powering methods, and wireless connectivity solutions. The traditional cloud-centering IoT systems are moving toward distributed intelligence schemes that impose strict requirements on IoT devices, e.g., operating range, latency, and reliability. In this article, we provide an overview of hardware-related research trends and application use cases of emerging IoT systems and highlight the enabling technologies of next-generation IoT. We review eco-friendly manufacturing for next-generation IoT devices, present alternative biodegradable and eco-friendly options to replace existing materials, and discuss sustainable powering IoT devices by exploiting energy harvesting and wireless power transfer. Finally, we present (ultra-)low-power wireless connectivity solutions that meet the stringent energy efficiency and data rate requirements of future IoT systems that are compatible with a batteryless operation

Wireless Localization Systems: Statistical Modeling and Algorithm Design

Wireless localization systems are essential for emerging applications that rely on context-awareness, especially in civil, logistic, and security sectors. Accurate localization in indoor environments is still a challenge and triggers a fervent research activity worldwide. The performance of such systems relies on the quality of range measurements gathered by processing wireless signals within the sensors composing the localization system. Such range estimates serve as observations for the target position inference. The quality of range estimates depends on the network intrinsic properties and signal processing techniques. Therefore, the system design and analysis call for the statistical modeling of range information and the algorithm design for ranging, localization and tracking. The main objectives of this thesis are: (i) the derivation of statistical models and (ii) the design of algorithms for different wire- less localization systems, with particular regard to passive and semi-passive systems (i.e., active radar systems, passive radar systems, and radio frequency identification systems). Statistical models for the range information are derived, low-complexity algorithms with soft-decision and hard-decision are proposed, and several wideband localization systems have been analyzed. The research activity has been conducted also within the framework of different projects in collaboration with companies and other universities, and within a one-year-long research period at Massachusetts Institute of Technology, Cambridge, MA, USA. The analysis of system performance, the derived models, and the proposed algorithms are validated considering different case studies in realistic scenarios and also using the results obtained under the aforementioned projects