Leonardo Lizzi

In this paper, an approach based on Machine Learning (ML) to predict the maximum achievable performance (fractional bandwidth and total efficiency) of a printed Inverted F-antennas (IFAs) integrated into compact IoT terminals is proposed. This original approach relies on the use of a Multi-Layer Perceptron (MLP) artificial neural network (ANN), which is trained using data from numerical simulations that take into account the constraints of practical implementations. The effectiveness of the approach is demonstrated through comparisons with numerical and experimental results, as well as with theoretical results available in the literature. The obtained results show that the proposed supervised regression ML model is capable of predicting the maximum achievable fractional bandwidth and total efficiency, with an accuracy of 95.9% and 98.6%, respectively.

Over the past few years, the Internet of Things paradigm has brought renewed significant interest to indoor positioning, tracking, and localization topics, principally since real-time locating technology allows a reference node to infer the position of tagged target nodes, creating the opportunity for millions of object-to-object awareness applications. This study first presents an overview of positioning localization techniques and discusses the use of ultra-wide bandwidth technology for complex environment monitoring, followed by consideration of the error sources that are present in line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios between a reader and a tag. A technical review of the available industrial and commercial UWB real-time locating transceivers (RTLSs) is presented, with a focus on the frontend antennas that are integrated in these systems to establish the needed wireless communication for positioning. Then, the different characteristics of these antennas are summarized and discussed, along with their impact on the localization performance in terms of the reading range, position information accuracy, object-orientation-independent localization, and multipath mitigation. Solutions are suggested to achieve antenna-based improvements to the performance of RTLSs.

A compact single-fed omnidirectional circularly polarized (OCP) antenna is presented. The circular polarization is obtained by combining an Alford Loop (AL) and a Wire-Patch (WP) radiating structures, which are used to generate two orthogonal E-field components. The antenna exhibits a clear right-handed circular polarization (RHCP) with a dipole-like omnidirectional radiation pattern. A prototype has been realized using two FR-4 printed circuit boards (PCBs) and experimentally tested. The measured overlapped -10 dB impedance matching and 3 dB axial ratio bandwidth is 120 MHz wide (4.9%) from 2.40 to 2.52 GHz. The measured RCHP maximum realized gain and total efficiency are 1.91 dBic and 87%, respectively. Its compact size (0.25λ × 0.25λ × 0.08λ), and its low-cost, robust, and easy-to-realize structure make this antenna suitable for IoT applications.

Wearable waveguide surfaces can be integrated into textiles to improve Wireless Body Area Networks (WBANs). In this work, a compact 30 mm x 30 mm dual-branch resonator end-launcher to enable communication through a waveguide surface manufactured with textile-compatible material at 2.4GHz is proposed. A 25 mm x 25 mm clearance zone area is respected for electronic component integration. The end-launcher topology uses a balanced dual-branch configuration to maximize electromagnetic coupling with the flexible waveguide surface. A design methodology is proposed to co-design the end-launcher and the waveguide surface. Experimental measurements on the human body torso are presented with 0.3 dB/cm insertion loss between 2.4 and 2.48 GHz. The final result is an autonomous, compact, wireless-contact, and battery-powered end-launcher for innovative clothing applications.

Long-Range Wide-Area Networks (LoRaWAN) allow the transmission of data via radio link from sensors, which are potentially isolated or difficult to access, to gateways and servers that are connected to cellular networks for data processing, exchange, or relay, with low transmission power. This concept employs Long-Range (LoRa) modulation and has led to the emergence of many applications for the monitoring and tracking of objects. However, due to its characteristic of a low data rate for low-power communication, the transmission of information with LoRa technology is not suitable for the fast real-time monitoring of data. Additionally, due to its narrow bandwidth, an attempt to perform localization through the LoRa modulation technique will result in very limited accuracy because of its inability to resolve multipath problems. Thus, in this paper, we propose a multi-standard Ultra-Wide Bandwidth (UWB) and LoRa end-device that is capable of measuring location with high accuracy using UWB technology and then transmitting the location information through LoRa method to gateways and the Internet of Things Network. The results of measurements in indoor and outdoor scenarios show a UWB localization accuracy that is of sub-meter level, being between 10 and 33 cm, and a UWB range of 124 m in Line-of-Sight (LOS) and 55 m in Non-Line-of-Sight (NLOS) applications, respectively.

Indoor object localization and positioning is part of the space-awareness concept which has seen a rising popularity in recent Internet of Things (IoT) research and applications. This article presents a novel method to improve the localization performance of ultra-wide band (UWB) real-time locating systems (RTLS) by improving the transmitting and receiving reader and tag antennas. Patch directional UWB antennas with relatively higher gain compared to the generally used standard omnidirectional monopole UWB antennas have been exploited to achieve a larger localization range. Furthermore, the patch antennas were designed to have wideband circular polarization to achieve two objectives: a received power independent of the orientation of the tagged objects that need to be detected, and the filtering of unwanted multipath signals. A measurement campaign was conducted using a commercially available RTLS with conventional antennas and then with the newly designed antennas. A comparison between the localization results of the two antenna types demonstrates an improved range with almost 100 m difference, received power independent of tag orientation, and increased multipath mitigation with the directional circularly polarized antennas.

A new compact multifunctional pattern reconfigurable 2 × 2 antenna array at 3.65 GHz with high gain and 16 (Multiple Input Multiple Output) MIMO modes is proposed. The single-element antenna includes 4 U-slots etched on the ground plane, with orthogonal slot orientations for polarization un-correlation, and fed using a reconfigurable feeding network with 4 PIN diodes. Hence, the single-element antenna is a pattern reconfigurable U-slot antenna with four pattern configurations. The average efficiency of 80%, the peak gain of 9.4 dB, and an overlapped -10 dB impedance-bandwidth of 200 MHz at a resonant frequency of 3.65 GHz in the n78 5G band are achieved. The single-element size is 55.5 × 54 mm ² , 0.66λ ₀ ×0.65λ ₀ . The horizontal and vertical distances between the U-slots in a single-element are 30 mm (0.36λ ₀ ), and 27 mm (0.32λ ₀ ), respectively. The 2 × 2 antenna array of such an element with a 58.5 mm (0.7λ ₀ ) between the elements occupies a volume of 140×140×21 mm ³ . The 2×2 elements provide 16 reconfigurable U-slots with two modes of operation, Array Mode and Multiple-Input-Multiple-Output (MIMO) Mode. For the MIMO Mode, the antenna has a maximum Envelope Correlation Coefficient (ECC) of 0.1194 between the radiation patterns and a minimum isolation of 20 dB between the four ports. For the array Mode, a 4×4 antenna array has a peak gain of 17 dBi, and a beam-steering range of -50° ≤ θ ≤ 50° in the two principle planes. The antenna is suitable for small cell base-station applications.

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This paper presents the effect of the polarization of antennas used in Ultra-Wideband systems for positioning applications. Measurements have been conducted using the DecaWave DWM1000 module and its antennas on both the transmitter (tag) and receiver (anchor) sides. The received power with the anchor-tag distance were measured with two configurations, co-polarization and cross-polarization of the two antennas. Results in real indoor scenario show that RSSI is strongly affected by the polarization sense for distance lower than 10m. For larger distance, the polarization mismatch has a negligible effect.