In the new scenarios foreseen by the Internet of Things (IoT), industrial and consumer systems will be required to detect and localize tagged items with high accuracy using cheap, energy autonomous, and disposable tags. This paper discusses system-level and circuit-level aspects to be adopted for future generation passive radio-frequency identification (RFID) tags with localization capabilities. It is argued that RFID-enabled localization strategies, combining ultra-wideband (UWB) backscattering for communication/localization purposes and UHF for “on demand” powering of battery-less tags can be successfully exploited to this purpose. The proposed architecture adopts a small number of reference nodes, acting both as UWB readers and as UHF power sources. Architectural and circuital considerations on different design choices for the UWB-RFID tag are discussed, focusing on available off-the-shelf components. Power budget constraints for UWB backscattering operation and UHF wireless powering are derived in worst-case conditions. Furthermore, the simulation results, verified with experiments, prove the feasibility of cm-level localization accuracy at distances of several meters even in indoor scenarios where multi-path fading might be present.

We present a self-sustained battery-less multi-sensor platform with RF harvesting capability down to −17 dBm and implementing a standard DASH7 wireless communication interface. The node operates at distances up to 17 m from a 2 W UHF carrier. RF power transfer allows operation when common energy scavenging sources (e.g., sun, heat, etc.) are not available, while the DASH7 communication protocol makes it fully compatible with a standard IoT infrastructure. An optimized energy-harvesting module has been designed, including a rectifying antenna (rectenna) and an integrated nano-power DC/DC converter performing maximum-power-point-tracking (MPPT). A nonlinear/electromagnetic co-design procedure is adopted to design the rectenna, which is optimized to operate at ultra-low power levels. An ultra-low power microcontroller controls on-board sensors and wireless protocol, to adapt the power consumption to the available detected power by changing wake-up policies. As a result, adaptive behavior can be observed in the designed platform, to the extent that the transmission data rate is dynamically determined by RF power. Among the novel features of the system, we highlight the use of nano-power energy harvesting, the implementation of specific hardware/software wake-up policies, optimized algorithms for best sampling rate implementation, and adaptive behavior by the node based on the power received.

This paper describes a digital signal processor based on a multi-context, dynamically reconfigurable datapath, suitable for inclusion as an IP-block in complex SoC design projects. The IP was realized in CMOS 090 nm technology. The most relevant features offered by the proposed architecture with respect to state of the art are zero overhead for switching between successive configurations, relevant area and energy computational density on computational kernels (average of 2 GOPS/mm ² , 0.2GOPS/mW) and relatively small area occupation (18 mm ² ), making it suitable for acceleration or upgrade of multi-core heterogeneous embedded platforms. The processor is delivered with a software tool chain providing the application developer algorithmic analysis and design space exploration based on ANSI C, with no utilization of hardware-related constructs or description languages

The computing demand of many signal processing algorithms is dramatically growing because of the increasing complexity of embedded software applications. Concurrently, as process technology scales, the design effort for realizing very large scale integrated circuits and the associated costs are becoming critically high. A possible solution to address this performance/costs challenge is given by customizable multiprocessor system-on-chips. The approach proposed in this paper leads to the customization of multi/many processor system-on-chip at two levels of abstraction: 1) customization through application-specific hardware accelerators implemented on configurable datapath that can target three kinds of structured application-specific integrated circuit technologies: metal, via, and runtime programmable and 2) customization of the architectural parameters of the platform. The proposed platform is equipped with a design framework that assists the user in the high-level design-space exploration of signal processing applications described using the Open Computing Language (OpenCL) language. A peculiar added value of the flow is to support the migration of OpenCL kernels and tasks into pipelined hardware accelerators described using a C-level language. The platform is able to provide an average performance of 90 GOPS on a set of reference signal processing applications, and an average computational energy efficiency of 130 GOPS/W in its metal-programmable configuration. This result shows the benefits in terms of energy efficiency of hardware customization applied to multiprocessor systems with respect to many core devices such as general-purpose graphic processing units, able to provide on average 2.5 GOPS/W for the applications under analysis.

This paper describes the architecture and the micropower design criteria of a battery-less, energy autonomous, individually addressable RF tag for UWB localization applications, with a focus on baseband circuitry. The tag includes a UHF rectifier, power conversion and management circuits, an addressable wake-up radio module, a microcontroller-based control unit, and circuits for UWB localization. The proposed circuit is suitable for UWB localization either by using passive backscattering of received UWB pulses, or by using active UWB pulses generators. Power for operation is scavenged from a modulated UHF carrier also used for addressing purposes. The circuit is implemented on discrete components in a 3.12 cm ² PCB area. The circuit can wake-up from fully discharged states and operates at distances as high as 10.8 m from a 2W-ERP source in the UHF 865-868 MHz RFID band with a +1.8 dBi receiving antenna. The quiescent power consumption of the tag is 3.88 μW, and the average power consumption at an addressing and activation rate of one time per second is 4.7 μW. The effectiveness of UWB localization was tested in a localization system based on time-difference-of-arrival (TDOA) estimations, consisting of multiple UWB readers and UHF transmitters.

The design of new a generation of smart tyre sensors directly powered by tyre motion, requires accurate information about electrical quantities related to electromechanical energy harvesters in realistic operating conditions. Transducers and circuits are not accessible inside tyres, and it is difficult to predict theoretically or numerically their behaviour. This paper presents a characterization methodology for energy harvesters in tyres based on wireless telemetry and on a series of specific measurements performed in an industrial-grade tyre test machine. A Wi-Fi modular telemetry platform is designed for acquiring inside tyres, at up to 14 kSa/s, open-circuit voltages up to ±160 V, and short-circuit currents up to ±18 mA, from piezoelectric transducers. A power estimation technique is executed locally to extract static power transfer characteristics. Measurements were performed in real-world conditions on commercial tyres in an industrial drum test machine operated at controlled speeds up to 40 km/h and axial loads up to 3 kN. Among its contributions, the paper analyzes the in-tyre behaviour of piezoelectric harvesters in terms of voltage, current, and power, and reports reference data from a relevant test environment to support power converter circuit design. To characterize joint in-tyre and energy-autonomous operation of piezoelectric transducers, power management circuits, and tyre sensors, fully functional electronic systems are validated on-field by the proposed telemetry platform. Validated circuits include passive rectifiers and synchronous electric charge extractors.