Jose Luis Gomez-Tornero

Indoor positioning for Internet of Things (IoT) and Industry 4.0 applications is increasingly required in Global Navigation Satellite System (GNSS)-denied environments. Radio-based systems commonly use received signal strength indicator (RSSI) measurements and fingerprinting. This work evaluates frequency-scanned leaky-wave antennas (FSLWAs), whose radiation patterns vary across Bluetooth Low Energy (BLE) advertising channels, against a monopole-based receiver architecture using unified-channel (UC) and separate-channel (SC) fingerprinting. Four established positioning methods are evaluated, with algorithm included as an adjustment factor in a factorial mixed-effects analysis. FSLWA-SC achieved model-adjusted reductions of 24.2–35.9% in the geometric mean of shifted positioning error, 𝑒 + 0.01 m, relative to the other configurations. Its performance advantage was also observed across the evaluated test days. The comparison concerns the complete installed receiver architectures, including their antenna placement.

The forthcoming sixth-generation (6G) wireless systems promote the convergence of cellular, Wi-Fi, and Internet of Things (IoT) networks. In this context, indoor IoT environments demand particular attention, as enhancing communication performance through the integration of sensing information becomes crucial in such scenarios. Thus, Integrated sensing and communication (ISAC) is poised to be a native technology for the 6G wireless networks. However, the vast majority of proposed works have developed sensing and communication technologies separately, and just a few integrate both technologies in a single prototype. To address this research gap, this paper proposes for the first time the integration of a smart leaky-wave antenna with the Wi-Fi protocol to enhance sensing-assisted communication in a cluttered indoor IoT environment. Due to the dispersive frequency-scanning response of a leaky-wave antenna, a highly directive beam pointing to different directions in space can be used to enhance communication performance. The manufactured prototype enables precise predictive beamforming largely unaffected by clutter echoes, leading to significant improvements in effective data rate compared to widely used commercial monopole and switched beam antenna solutions.

A compact planar multibeam antenna array for two-dimensional (2-D) beam scanning in the 5 GHz Wi-Fi ISM band, is presented. The array is composed of four half-width-microstrip leaky-wave antennas (HWM-LWA) that are interconnected by $4\times 4$ microstrip Butler matrices. By combining the frequency beam-scanning response of the LWAs and the beamforming mechanism of the Butler matrices, the synthesis of 32 directive beams using 4 channels of the Wi-Fi band is demonstrated. A wide scanning range from −60° to + 60° along the elevation plane is achieved using a narrow frequency band from 5.18 GHz to 5.72 GHz, and a scanning range from −45° to + 45° in the perpendicular plane through beam switching. Compared to other multibeam antennas in previous literature, this novel topology shows the most compact planar design, while offering the widest 2-D scanning range in such narrow scanning bandwidth.

We demonstrate the application of a Bull's-Eye (BE) leaky-wave antennas (LWA) for enhanced conical direction finding, leveraging its inherent conical-beam frequency-scanning capability. Unlike uniform or quasi-uniform 2D LWAs, such as Fabry-Perot Antennas, the 2D periodic BE-LWA uses a higherorder space harmonic to radiate. This enables the use of both backward- and forward-scanning frequency bands to improve the conical direction-finding performance, when compared to the use of a single scanning band. Also, the BE LWA presents rotational symmetry and thus more stability in the direction finding performance for any azimuthal angle. This is demonstrated with experiments using a printed-circuit BE LWA offering a total scanning operating band from 14 GHz to 32 GHz and covering an elevation field-of-view of 120° with fully-azimuthal symmetry.

In this work, we propose the use of a radial ray-tracing approach to accurately model the radiation from leaky-wave antennas (LWA). The technique involves the launching of several sets of rays that emanate radially from different source points along the LWA aperture. The trajectory of the emitted rays is determined and applied to accurately evaluate the impact of every source point on the radiation pattern of the LWA, with particular attention to complex setups incorporating dielectric lenses. Each source point's contribution is superimposed, weighted by a complex factor related to the LWA's leaky mode. The method demonstrates both efficiency and accuracy in modeling radiation patterns for different taperings of the leaky mode used to generate shaped beams, leading to a significant reduction in computation time compared to commercial full-wave solvers.

The application of one-dimensional bi-directional fed frequency-scanning leaky-wave antennas for proximity sensing is studied in this work. Using the two opposite ports of a microstrip antenna, a nearfield focused radiation pattern which varies with frequency is obtained. This type of frequency-diverse pattern can be used for sensing in the Fresnel region of the antenna. A simple half-width microstrip leaky-wave antenna with 35 cm of length is designed to operate in the 5.5 GHz band. The successful synthesis of nearfield focusing patterns on the proximity of the antenna, and which strongly vary in the frequency range from 5.18 GHz to 5.72 GHz, is theoretically and experimentally demonstrated. Finally, it is illustrated how this type of antenna can be applied to sense in a region of 50 cm x 50 cm surrounding the aperture.

This paper proposes a frequency-scanning antenna designed to operate in the 400 MHz to 800 MHz band for solar radio astronomy applications. It is constructed with perforated metallic walls and cylinders, that form a rectangular leaky waveguide. By adjusting the metallic cylinders in the appropriate subwavelength holes, the scanning angle of the directive beams and directivity can be effectively controlled while assuring high radiation efficiency and gain. Unlike previous leaky waveguides, the proposed design allows manual tuning of both the leaky-mode phase and the leakage factors. A 2-meter-long antenna prototype has been fabricated, and the measurement results show an angular scanning range from 70∘ to 30∘ above the horizon, with a peak gain of 14 dBi and radiation efficiency exceeding 70% over the entire scanning band. The application of this antenna to detect solar radio bursts without the need for Sun tracking is demonstrated.