The paper describes the FPGA implementation of a novel position evaluation algorithm based on the time difference of arrival (TDOA) principle that combines the characteristics of an Orthogonal Frequency Division Modulation (OFDM) symbol with the properties of the Zadoff-Chu mathematical sequences. The resulting system is highly scalable and its characteristics are easily adaptable to different operating scenarios. The algorithm has been implemented using the Stratix IV-E EP4SGX70HF35C3 FPGA, requiring about 112k bit of memory and less than 44k logic elements of which about 16k are registers. The paper describes the algorithm and its FPGA implementation along with experimental results validating the system performance even in the presence of multipath interferences and showing precision in target position estimation that is better than 2 cm.

In recent years, Real-Time Localization Systems (RTLS) are gaining significant attention from the scientific community. Usually, RLTS rely on positioning techniques based on the electromagnetic (e.m.) propagation properties of the received signals. Among the many possible approaches, RTLS based on the Angle-of-Arrival (AoA) estimation allows for accurate results with a comparatively lower number of receivers. In this work, we propose a novel, fully digital synchronous architecture for AoA estimation based on phase interferometry. After reviewing the state-of-the-art on full-hardware techniques for localization, the main blocks composing the proposed architecture, are discussed in detail, along with their dimensioning equations. The granularity with which the system estimates the phase shifts used to compute the AoA is reconfigurable according to the desired accuracy. The architecture is lightweight and computes the AoA in real-time. To validate the proposed approach, the RTLS architecture has been implemented on an Intel Cyclone IV E EP4CE115F29C7 FPGA board interfaced with a custom-designed receiver front-end, and experimental results on benchmark applications have been collected and analyzed.

This work introduces a novel coarse positioning system based on the estimation of the Angles-of-Arrival (AoAs) of Signals of Opportunity from a spacecraft in the Low Earth Orbit. The AoA estimation is done in real-time using phase interferometry through a dedicated hardware architecture. The 2D position is achieved by means of a simplified geometrical model based on the estimated angles. The experimental campaign aimed to assess the fit of the proposed model with reality, the AoA estimation accuracy, and the final positioning error. Results showed that the system can track the angular position of a fast-moving spacecraft with a precision of tenths of a degree. The final positioning accuracy demonstrates the effectiveness of the system for real-time coarse positioning.

Time synchronization is a topic of interest for any distributed system and it is of particular relevance in Wireless Sensor Networks (WSN), especially when it is necessary to keep a strong level of time synchronization among the data coming from different nodes, which are then employed to perform a posteriori data-fusion and data-merging operations. A special case of WSN is constituted by Wireless Body Area Networks (WBAN). The paper introduces the Fractional Low-power time Synchronization Algorithm (FLSA), a lightweight and ultra-low-power time synchronization algorithm conceived for Wireless Body Area Networks. The core of the proposed approach is the fractional-time concept, borrowed from Phase-Locked Loops theory, that allows achieving fine timer corrections. Moreover, an heuristic routine managing the on/off switching of the radio section of the device allows to dramatically decrease the power consumption. The mathematical discussion, along with a set of experiments is presented, proving the benefits associated with the proposed algorithm.

In modern medicine, smart wireless connected devices are gaining an increasingly important role in aiding doctors’ job of monitoring patients. More and more complex systems, with a high density of sensors capable of monitoring many biological signals, are arising. Merging the data offers a great opportunity for increasing the reliability of diagnosis. However, a huge problem is constituted by synchronization. Multi-board wireless-connected monitoring systems are a typical example of distributed systems and synchronization has always been a challenging issue. In this paper, we present a distributed full synchronized system for monitoring patients’ health capable of heartbeat rate, oxygen saturation, gait and posture analysis, and muscle activity measurements. The time synchronization is guaranteed thanks to the Fractional Low-power Synchronization Algorithm (FLSA).

This work introduces a process to optimize the design of a down-conversion mixer using an innovative strategy based on the g_m/I_D methodology. The proposed process relies on a set of technology-oriented lookup tables to optimize the trade-off between gain, power dissipation, noise, and distortion. The design is implemented using a 0.13 μm CMOS technology, and to the best of our knowledge, it possesses the best (post-layout simulation) figure of merit (FOM) among the works presented in literature. The FOM is defined as the product of gain and third-order intercept divided the product between average noise figure and power dissipation. Finally, the core of the mixer takes only 31 µm by 28 µm and it draws a current of 1 mA from the 1.5 V DC supply.