Programa del congreso

This paper presents a preliminary investigation into the relationship between UHF RFID signal characteristics (Received Signal Strength Indicator - RSSI and phase) and the vertical distance between the reader antenna and a water surface. Due to experimental constraints preventing direct soil moisture measurement, the study was adapted to use a 50-liter container filled with water, varying the reader height and transmission power. Initial manual data inspection revealed an apparent linear relationship between the signal phase and reader height, as well as between phase and the volume of water added (affecting water level). We outline the modified experimental methodology and propose the use of Feedforward Neural Networks (FFNN) for baseline modeling and Sparse Gaussian Process Regression (SGPR) to model the observed relationships and quantify measurement uncertainties efficiently. This work serves as a foundational step towards developing robust RFID-based liquid level or moisture sensing techniques, providing a methodology for controlled experimentation and data analysis using scalable probabilistic machine learning models. Data and code are intended for release via a public repository.

Planar microwave sensors have become very popular for early detection of anomalous samples. The resolution of these sensors can be improved applying loss compensation through an active feedback loop, and a systematic and precise design of these sensors can be performed based on stability analysis of feedback systems. This paper proposes a standalone oscillator-based active sensor formed by a Complementary Split-Ring Resonator (CSRR) and a Colpitts oscillator. These components have been designed according to the Normalized Determinant Function (NDF) for operation at the single frequency of 3 GHz, and good agreement has been obtained with the spectral response obtained through non-linear simulation. The sensing capability of the oscillator has been tested evaluating the impact of increasing the permittivity, observing a significant resolution improvement. However, the limitations in the dynamic range of the sensor hinder the detection of variations in losses. Experimental results will be presented at the conference.

La identificación y localización de la abeja reina en el interior de una colmena es fundamental para la reproducción y el funcionamiento de la colonia. Tradicionalmente, la localización de la abeja reina se ha realizado de forma tediosa mediante inspección visual de cada uno de los panales de la colmena, diferenciando a la abeja reina del resto con una marca de pintura en el tórax. Recientemente, se han desarrollado etiquetas RFID con un tamaño adecuado para ser pegado en el tórax de una abeja, lo que podría permitir tanto su identificación como localización de una forma más eficiente. En este trabajo se han llevado a cabo medidas de cobertura de un sistema RFID en la banda de UHF con una etiqueta situada el interior de la colmena en diferentes posiciones en cada panal y con la antena del lector localizada en el exterior de la colmena. Los resultados muestran que, si hay cobertura, la etiqueta podría ser localizada con una incertidumbre de 2 panales.

Este trabajo presenta el diseño y la evaluación de una agrupación de antenas cilíndrica para lectores RFID en la banda UHF, compatible con las normativas ETSI, FCC y las bandas WiFi de 2.45 GHz. La agrupación está compuesta por 12 antenas monopolo de banda ultraancha (UWB), dispuestas en una configuración de 6×2. Se introduce un plano de tierra en forma de U para mejorar la directividad sin comprometer el ancho de banda. La celda unidad, fabricada sobre un sustrato FR-4, fue optimizada y replicada para formar la agrupación completa. Simulaciones electromagnéticas de onda completa realizadas en CST Studio Suite confirman el buen acoplamiento de impedancia y la reducción del acoplamiento mutuo. La agrupación alcanza un ancho de banda del 37.9 % entre 800 MHz y 1.15 GHz, con niveles de acoplamiento mutuo inferiores a –15 dB en todas las bandas de operación RFID. El control del diagrama de radiación se demuestra mediante la excitación de diferentes puertos, alcanzando valores de directividad de hasta 6.87 dB y una eficiencia total de 0.55 dB. Estos resultados validan la idoneidad de la agrupación para una detección robusta y flexible de etiquetas RFID en entornos electromagnéticos complejos.

This communication presents the design and comprehensive evaluation of an RFID reader antenna tailored for UHF applications (868-915 MHz). The proposed design incorporates a metallic rectangular cavity, two arc-shaped planar feeding elements, and an annular slot extruded on the upper surface of the cavity. By combining these elements, the antenna achieves an operational bandwidth of 11.4 % and a directivity of 8.13 dBi at 868 MHz and 8.49 dBi at 915 MHz. Moreover, the antenna consistently maintains an axial ratio below 1.6 dB at both frequencies, ensuring excellent circular polarization performance. The radiation pattern's 3 dB beamwidth exceeds 71 degrees, which provides a wide coverage area suitable for complex communication environments. These performance characteristics demonstrate that the proposed antenna design is highly effective for enhancing the reliability and efficiency of RFID systems in various industrial and logistics applications.

Quantum Rydberg atom-based radio frequency (RF) sensors exploit the exceptional sensitivity of highly excited atomic states to detect electromagnetic fields with very high precision, offering potential advances in telecommunications, radar and microwave radiometer systems, GNSS-Reflectometers, and electromagnetic compatibility testing. This study presents a detailed MATLAB simulation analysis of radio-frequency sensors modeled as a five-level rubidium-87 (Rb-87) system under the influence of RF and optical fields. The simulation leverages the Lindblad master equation to capture the coherent evolution, the spontaneous emission, the collisional dephasing, and the field-induced ionization. For an external RF electric field of E0 = 100 mV/m, a frequency sweep from 10MHz to 10GHz reveals the impact of noise: an ideal case just limited by quantum noise yields a sensitivity of 0.01 μV/m/√Hz and a SNR of 177dB, while for E0 = 10 mV/m and a realistic noise (−130 dBm/Hz) the sensitivity worsens to 72 − 633 μV/m/√Hz and a SNR of 72 dB. The study investigates the effects of RF field amplitude, atom density, and environmental parameters such as residual magnetic field and ambient temperature, in the sensitivity and bandwidth of these promising receivers, offering a framework to optimize Rydberg-based sensing technologies for Earth Observation, Communication and Navigation systems.