A low profile, miniature, horizontally polarized loop antenna is proposed to work in the 400-450 MHz UHF band. The wide band coverage is obtained through continuous frequency reconfiguration through varicap loaded ends of the loop. A study on miniaturization effects on performance as well as on matching loads is presented. After the optimization the proposed antenna confirms to work as a magnetic dipole with a total efficiency greater than 90% between 400 MHz and 440 MHz.

A compact circular Alford Loop antenna design is proposed to work at 400 MHz and 440 MHz UHF bands for satellite-based IoT applications. The frequency reconfiguration mechanism is based on PIN -diode switching. The design of a matching circuit to allow the diodes DC bias over the RF structure is presented, with a focus on practical discrete surface mounted components. Measured results on a prototype of the antenna agree with simulations, confirming the horizontal polarization and frequency switch by simply applying a DC bias over the antenna's SMA connector. The compactness and radiation characteristics of this antenna make it a good candidate for new generation of low-cost IoT satellite-based communication's ground station.

This work proposes the use of a two-element MIMO antenna decoupled by a neutralization line to combine RF energy harvesting on one port and backscattering on a second port. The use of two coupled antennas allows for improving energy conversion efficiency on one port while communicating at the same time, by modulating the impedance on the second port. The proposed antenna, connected to two independent circuits, operates in the UHF band at 867 MHz. A theoretical study is validated by simulation and practical measurements.

This article proposes a dual-band, dualpolarization antenna system for 5G small cells based on the aperture-shared antennas principle. The system supports MIMO capabilities in the sub-6 GHz band and enables 30degree beamforming in the millimeter-wave band. The lowband antennas are perforated square patches operating at 3.6 GHz, while the high-band antennas consist of three subarrays of four crossed patches designed to operate at 26 GHz. Simulated results demonstrate bandwidths of 154 MHz in the microwave band and 1.73 GHz in the millimeter-wave band, with maximum gains of 6.93 dBi and 9 dBi, respectively. Millimeter-wave beamforming is achieved by activating specific ports.

In this paper, the design of a wide-band Archimedean Spiral antenna is presented for L-band and S-band communication. The concept is using low-cost FR4 substrate and can achieve a realized gain higher than 3dBic from 1500 to 2500 MHz.

The Internet of things is increasingly focused on UAV-based long-range applications. This necessitates versatile, low-cost antenna designs for both ground stations and drones. This study proposes the design of a pattern reconfigurable parasitic element antenna system operating in the LoRa 868 MHz band and its on-field characterization. The electronic steerable parasitic array radiator (ESPAR) antenna consists of a single-fed shorted patch surrounded by four rectangular parasitic elements. The antenna system can develop four directive beams, each activated by one of four PIN diodes, and an omnidirectional pattern obtained when all diodes are turned off. The antenna has been characterized both in an anechoic controlled environment and in a practical on-field drone-to-ground packet transmission scenario. Results based on received signal strength indicator (RSSI) show that the pattern reconfigurability becomes increasingly relevant with the end-point distance and that pointing the beam at the end point always allows the highest RSSI level to be received.

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.

In this paper, the design of an antenna array for small 5G base stations, also called "small cells", operating in the 26 GHz millimeter band is proposed. Based on a single feeding circuit, this structure has dual polarization and diversity in radiation pattern. Simulated results show a maximum gain of 8.9 dBi and a maximum HPBW of 64° for this structure.

A 6 direction pattern reconfigurable Electronically Steerable Parasitic Array Radiator (ESPAR) system is proposed to work at 5.075 GHz, in the C-Band dedicated to unmanned aerial vehicles. This single fed antenna can switch among 6 directive beams across the whole azimuth plane, thanks to the coupling with its parasitic elements. The directional reconfiguration is enabled by changing reactive loads on each parasitic element. The proposed antenna is light weight, low profile and high gain in each directive state. Measurements on a static single beam configuration and simulated results on the reconfiguration circuit are presented to confirm the effectiveness of the design principles.

A frequency reconfigurable dual band Planar Inverted-F Antenna (PIFA) dedicated to operate in industrial environments is proposed for Internet of Thing (IoT) and Narrow-Band (NB)-IoT applications. The proposed dual-band structure comprises an active element and a parasitic element. These two elements cover initially (698-708 MHz) and (878-888 MHz), respectively. The insertion of two varactors diodes MA4ST405-287 T (one in each element), which offer a capacitance range from 3.11 pF to 69.45 pF, allows their frequency reconfiguration to cover the IoT and NB-IoT bands B28 (703-803 MHz), B20 (791-862 MHz) and B8 (880-960 MHz).

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.

A pattern reconfigurable antenna system for LoRa 868 MHz communications is characterized in a practical case scenario involving Drone-to-Ground communications. The effectiveness of the beam-steering antenna is confirmed through Received Signal Strength Indicator (RSSI) airborne measurements, which indicate that the reconfiguration becomes more efficient as the distance increases.

A pattern reconfigurable parasitic element antenna system is proposed to operate in LoRa 868 MHz band. As part of a sensor for real-time air quality monitoring in urban spaces, the antenna system is composed of a single-fed wire-patch radiator surrounded by 4 shorted parasitic patches used to reconfigure the radiation pattern in 4 configurations through the use of PIN diodes.

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.

This paper presents the design of an antenna dedicated to cohabiting with photovoltaic cells of solar panels. The proposed broadband solution uses stacked aperture-fed patches with a solar cell as an upper parasitic element. In this approach, the solar cells' functionality and the antenna's performance can be optimized despite the cohabitation in a small volume. The antenna is intended to operate in the B66, B3, B4, B25, B2, and B1 (1710-2200 MHz) frequency bands. In the proposed solution, three solar cells are connected in series to generate the desired DC power while radiating simultaneously. The relative simulated bandwidth of this antenna achieves 27%.

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.