Programa del congreso

This paper demonstrates for the first time a dual polarization reconfigurable reflectarray antenna based on Liquid Crystal (LC) that operates at W-band. The antenna is electrically large and is capable of independently steering the beam of two orthogonal polarizations. Two different implementations of single-layer unit cells (single resonant and multi-resonant) capable of providing suitable phase range to independently control the two RF polarizations with enough isolation have been investigated. The single resonant cell was finally used to design a complete reflectarray antenna made of 55X55 elements, for which an accurate and efficient modeling of the cells was implemented. The antenna shows 35º of 1D scanning range with 25dBi gain and a maximum SLL of -9dB in the entire range for both polarizations at 98 GHz.

This paper presents an electrically large multi-faceted aperture that can be folded and deployed onboard an aerospace vehicle. Following a single-offset configuration, the aperture comprises five low-profile panels assembled edge-to-edge, arranged following a parabolic curvature. The entire antenna structure is designed to generate a directive beam in Ka-band, working in dual-linear polarization. An electromagnetic characterization of this topology has been carried out, compared the results to the performance of an equivalent single facet reflector and a multi-faceted reflectarray composed of nine panels. The five panel multi-faceted structure features a directive pattern stable in-band, and a 1dB-gain bandwidth of 10%, significantly higher than in an equivalent single facet aperture. Compared with the nine-panel structure, it exhibits lower gain bandwidth but higher peak gain, similar beamwidth in-band and easier integrability with the vehicle platform.

En el contexto de transmitarrays de doble banda, el diseño de celdas unitarias presenta grandes desafíos debido a la necesidad de cumplir con especificaciones de fase simultáneas e interrelacionadas en ambas bandas de frecuencia, esenciales para funcionalidades como el direccionamiento de haz a través del desplazamiento mecánico de la alimentación. Este estudio introduce un enfoque efectivo para el diseño de celdas unitarias, aprovechando una implementación personalizada del método de los momentos en el dominio espectral (SD-MoM, por sus siglas en inglés). Este método permite calcular la respuesta de onda completa de las celdas unitarias a un coste computacional significativamente menor en comparación con el software comercial de propósito general (de dos a cuatro órdenes de magnitud). La metodología emplea una estrategia novedosa que implica un algoritmo genético para ayudar en la búsqueda de soluciones óptimas de celdas unitarias. Esta estrategia es factible debido a la eficiencia y precisión del SD-MoM en la evaluación de cada función de fortaleza. Como demostración práctica, se diseña un conjunto de celdas unitarias para operar en comunicaciones satelitales de banda Ka, específicamente en las bandas de frecuencias de 19.7-20,2 GHz y 29.5-30 GHz. Las celdas unitarias resultantes muestran un grosor sustancialmente reducido en comparación con diseños anteriores destinados a las mismas bandas de frecuencia.

This paper presents a guide to design unit cells for reflectarrays and transmitarrays based on unit cells with 3-D geometry. To explain the design process, a metal-only unit cell with basic 3-D geometry in a periodic environment is considered. The parts to be considered in the 3-D unit cell structure as well as their importance in the electromagnetic behavior in reflection are described. The inclusion of an impedance transformer at the interface between the 3-D unit cell and the free space is analyzed. Based on the design of the 3-D unit cell in reflection (for reflectarray design), its modification for transmitarray design is introduced. Finally, design strategies to modify the phase in transmission in 3-D unit cells are described and one of them based on meandered lines is assessed and discussed.

This article presents the theoretical study and numerical simulation for the implementation of a stub resonator in the microstrip ridge gap waveguide (MGCW) transmission line. The resonator is filled with liquid crystal (LC) and, thanks to LC’s dielectric anisotropy properties, the resonance can be easily controlled using an external electric or magnetic bias field. The resonance was designed to operate in the range of 7.8 to 8.8 GHz. Its frequency response, associated to both parallel and perpendicular LC’s permittivity, as well as intermediate state were computed. Finally, the results are discussed.

In this paper, we describe the design of a periodically air-filled substrate integrated waveguide (SIW) bandpass filter in which part of the dielectric substrate is removed to reduce insertion losses. The unit cell parameters of the structure, which are directly related to the center frequency (fc) and bandwidth (BW) of the first passband, and also to the first stopband or bandgap (BG) of the structure, have been appropriately selected for filtering purposes, thus providing some useful design rules. Furthermore, we apply the concept of glide symmetry for achieving a much larger fractional bandwidth (FBW). Additionally, a microstrip-to-SIW transition including a novel coupling iris is proposed. A prototype of the periodic SIW filter with glide symmetry has been manufactured and measured for validating purposes. The proposed filter proves to be a good candidate for millimeter wave applications.

This paper introduces a theoretical framework for deriving fully analytical and multi-modal equivalent circuits for periodic structures and metasurfaces in general. By introducing time as a new variable, classical versions of circuits for purely spatial scenarios are expanded to account for spacetime-varying ones. Throughout the document, various periodic structures are examined from a circuit perspective, exhibiting periodicity in space, time, and spacetime. The efficiency of the analytical circuits is confirmed through external full-wave solvers, affirming the models as valuable tools for investigating innovative and advanced spacetime scenarios.

A design methodology to realize Fabry-Pérot cavity antennas with very high aperture efficiency and improved bandwidth is presented. The antenna is based on a tapered Partially Reflective Surface, and its characteristics are determined through a combination of criteria from the simplified ray-model and the 2D leaky-wave approaches. Therefore, through a transmission line modelling of the PRS, its cells can be chosen to follow the required leakage factor function while satisfying the resonance condition and the positive phase-slope technique. Two different designs are carried out to present a quasi-uniform aperture field distribution. Their simulated behaviours are compared with the best design of a previous work, clearly showing the improvement achieved from incorporating the leaky-wave theory into these antennas.

The development of a Leaky-Wave Antenna based

on Bianisotropic Huygens’ Metasurfaces and using GAP waveguide

technology is presented in this work. The waveguide is

designed with horizontal polarization of the mode at 20 GHz,

different than the conventional vertical polarization. Additionally,

a uniform leaky-wave antenna designed just slotting the top

surface of the waveguide is compared with the same structure

but combining the slot with the Huygens’ metasurface which

change the radiation angle of the LWA to the desired broadside

radiation pattern.

We discuss the issue of identifying the forward/backward nature of the modes in bounded one-dimensional periodic structures. This identification relies on the possibility of adequately and uniquely defining the phase velocity in these types of structures. We propose a general definition of phase velocity for scalar one-dimensional waves and show that, according to that general definition, the voltage and current waves in lossless nonhomogeneous transmission lines with positive inductance and capacitance parameters are necessarily forward waves. In more general scenarios, we show that an appropriate definition of the phase velocity can still be found for electromagnetic waves with at least one linearly polarized field and that they also are necessarily forward waves if they propagate through media with positive permittivity and permeability.

Time domain simulations of electromagnetic problems are intrinsically interesting for engineering purposes, not only from the physical point of view but also from the computational effort. These approaches rely on a marching on time schemes where the field solution can be obtained from previous time steps in an increasing manner. However, each new sample requires computations with a small complexity (typically matrix-vector multiplications) but within a large approximation dimension, which clearly deteriorates the simulation time.

A model order reduction approach for finite element method in time domain (FEMTD) simulations for microwave devices using time as a parameter is proposed in this work. This methodology shows the possibility to solve time evolution problems in electromagnetics requiring a small computational effort. Indeed, the system matrices involved in the model order reduction technique are pretty small. This is in contrast to the large dimension matrices arisen in traditional FDTD and FEMTD approaches.

Several microwave circuits, such as an electromagnetic band gap structure and dielectric resonator filter, will show the capabilities and possibilities of this new approach for time domain simulations in electromagnetics.

The motivation behind the research lies in the necessity to identify indoor applications for 6G to contextualize and render practicality to the proposed work. While terahertz communication holds promise for achieving ultra-large bandwidths and Tbit/s speeds, the primary challenge lies in implementing transceivers suitable for integration into indoor and pico-cells WLANs for 6G applications. The proposed FSS architecture addresses these challenges by introducing a low-profile design that not only overcomes volumetric constraints but also reduces system complexity, thus enhancing cost-effectiveness and facilitating mass adoption across diverse technological domains. This innovative approach enables the implementation of dual polarization in both Co-Polar (CP) and Cross-Polar (XP) operations without the need for intricate multiport networks, thereby simplifying the system architecture and enhancing its versatility. The FSS design offers ultra-large bandwidth circular polarization fields in reflection mode, capable of providing two separate bands for each circular polarization, making both CP and XP operations feasible with minimal changes in phase, thereby paving the way for future 6G communications systems. The Design is manufactured and measured, presenting good relation with respect to the simulations

Currently, vortex beams with orbital angular momentum (OAM) are of great interest as they are a key element in increasing the capacity of communication links. This article presents an analytical study comparing the purity of OAM vortex beams generated using a metasurface illuminated with three different excitations. The transmissive metasurface has been designed to operate in the millimeter-wave frequency range, and consist of 33×33 two-layered H-shaped meta-atoms. The phase is implemented following the Pacharatnam-Berry (PB) principle. High OAM purity votex beams are obtained, with values of 75%, 90%, and 95% for the uniform, circular uniform and Gaussian excitations respectively confirming both the correct functionality of the metasurface and the effect that different excitations have on OAM quality.

Multiple-Input Multiple-Output (MIMO) systems play a crucial role in fifth-generation (5G) mobile communications, primarily achieved through the utilization of precoding matrix techniques. This paper presents precoding techniques employing codebooks in downlink MIMO-5G wireless communications, aiming to enhance network performance to meet the overarching 5G objectives of increased capacity and reduced latency. We conduct a comparative analysis of various precoding techniques outlined by the 5G standard through diverse simulations across different scenarios. These simulations enable us to assess the performance of the different precoding techniques, ultimately revealing the strengths and weaknesses inherent in Type I and Type II codebooks.

Sustainability is a critical factor in the development of future beyond-5G (b5G)/6G networks. This work highlights the importance of energy efficient practices to reduce environmental impact and resource consumption, in line with the objectives of the International Mobile Telecommunications (IMT) 2030. The increasing energy consumption in telecommunications networks highlights the need for corrective action without compromising network performance or security. The paper presents an Open Radio Access Network (O-RAN) architecture for 5G networks that enables the monitoring and optimization of energy consumption. The study integrates xApps and rApps into various emulated network elements to provide a real streaming service while monitoring the power consumption of the different network elements.

As Open Radio Access Network (O-RAN) architecture gains prominence, it also introduces new security challenges particularly concerning the open interfaces, virtualization and the intelligence embedded within the network. This paper makes an overview of the security of this architecture and presents a testbed for the extraction of different metrics for an E2E video service under two situations: with and without attack. This testbed can be used to generate datasets and evaluate the impact of poisoning and evasion on network intelligence.

The evolution of mobile networks is currently going through a stage of opening up the infraestructure, known as O-RAN, a paradigm that also proposes providing more intelligence to the Radio Access Network (RAN) of the users. The key element that allows this change is the RAN Intelligent Control (RIC). Possible service improvements to customers are affected by new security breaches that may occur on the network. This paper analyses the impact of poisoning and evasion attacks, where training and testing data, respectively, are altered on Machine Learning (ML) algorithms. To this end, an E2E scenario has been analysed, in which the direct effects of the users' perception is studied.

With the advances in 5G, and beyond,

mobile communications, more focus is directed toward implementing

massive MIMO. While numerous solutions exist for

high-frequency bands exceeding 1GHz, exploration of increasing

MIMO order in low-frequency bands has not been yet explored,

despite their unique characteristics as wide coverage area and

penetration through obstacles that are essential for covering a

massive number of connected devices. The challenges of designing

antenna base station arrays that can support massive MIMO

at 5G New Radio (5G NR) 700 MHz bands are summarized.

Here, the goal is to move from the current non-massive 4T4R

solution to a massive 16T16R MIMO without the increase in the

overall size of the base station (restricted to standard sizes) or

sacrificing array performance, especially in terms of bandwidth, gain,

beamwidth, and isolation. Results based on an array version of

differential metallic cap-loaded multi-layer Dielectric Resonator

Antenna (DRA) are presented.

In beyond 5G cellular systems, Network Slicing (NS) functionality allows splitting a physical network into several logical slices tailored for a specific application. In sliced networks, a slice-aware automatic optimization of Network Functions (NFs) is key to guarantee Service Level Agreement (SLA) compliance while minimizing operation costs. For this purpose, with the advances in artificial intelligence, massive data collected in the operations and support system can be leveraged to develop Deep Reinforcement Learning (DRL) solutions deriving optimization policies automatically. This work proposes the first algorithm for slice-aware traffic steering based on DRL. The algorithm trains a slice-specific double deep Q-learning agent that learns the optimal traffic steering policy to improve SLA compliance per slice. Simulation results have shown that the proposed algorithm outperforms other slice-aware traffic steering approaches, increasing SLA compliance on 11\% in a realistic scenario with 3 slices serving uRLLC, uLBC and eMBB traffic.

This paper examines the non-idealities inherent in commercially available beamformers and explores their implications in the calibration procedures for phased array antennas. The non-ideal nature of the beamformer is meticulously modeled and assessed through extensive S-Parameter measurements to discern its impact on analyzed excitation retrieval methods. The Rotating-element Electric-field Vector (REV) and Control Circuit Encoding (CCE) methods are simulated using a synthetic array with spherical wave expansion driven by output coefficients measured from the beamformer. Simulations are executed to compare the REV method with a Selective-REV variant, designed to enhance coefficient prediction accuracy by leveraging a priori knowledge of phase-shifter amplitude deviations. Additionally, amplitude, phase, and complex CCE encodings are employed to determine the encoding technique that best accommodates beamformer non-idealities. Finally, anechoic chamber measurements assess the pattern prediction capabilities of the calibration methods explored in the simulation.

En los sistemas 5G y posteriores, Network Slicing (NS) permite el despliegue de múltiples redes lógicas personalizadas para sectores verticales específicos sobre una infraestructura física común. En la red de acceso radio, los operadores móviles necesitan modelos para predecir el rendimiento de los segmentos de manera proactiva, anticipándose a posibles degradaciones en la red.

Este trabajo aborda la previsión del rendimiento de los segmentos a corto plazo mediante el aprendizaje supervisado haciendo uso del algoritmo de predicción Time Series Mixer-Only.

En concreto. se evalúan cuatro estrategias de entrenamiento basándose en series temporales realistas de rendimiento por segmento, series temporales sintéticas o

una combinación de ambas.

La evaluación del rendimiento se lleva a cabo con un conjunto de datos realista generado mediante simulación en una red con 4 segmentos que ofrecen servicios con diferentes modelos de tráfico y requisitos de rendimiento a usuarios terrestres y aéreos.

Los resultados muestran que el uso del aprendizaje por transferencia para combinar

datos sintéticos y de rendimiento del segmento correspondiente

es un enfoque prometedor, con un mejor rendimiento que el método Random

Walk para un horizonte temporal de 30 días en todos los segmentos.

In 5G networks, densification of network elements is a key point for a fast and efficient deployment of this technology. This technique consists of adding small cells in areas where traditional cells have coverage problems or where there is a high flow of users, affecting their capacity. Therefore, the coordination and relationship between these cells during deployments must be managed efficiently. With the current advances in artificial intelligence for network management and automation tasks, this task can be automated through supervised learning. This paper proposes an automatic method to estimate neighborhood relationships between cells during deployments using deep neural networks. The evaluation of the model has been performed using a dataset extracted from a real LTE network. The results show that the proposed method promises to improve upon current neighborhood relationship algorithms.

Se prevé que las redes de sexta generación (6G) soporte una amplia gama de tecnologías por lo cual es necesario que estas redes ofrezcan servicios de alta calidad, con lo cual el

concepto de confianza desempeña un rol fundamental para cumplir con los retos de las redes 6G. En este artículo se realiza una revisión de los conceptos de confianza y las metodologías y técnicas usadas para garantizar un ecosistema 6G seguro y confiable, para esto se hace una categorización de las técnicas de evaluación de la confianza basada en el campo de estudio que aborda cada técnica. Por último, se presenta un análisis de las

diferentes técnicas en base a los enfoques definidos en cada categoría, en donde se presentan los retos técnicos, ventajas y desventajas que supone el uso de cada una de las técnicas revisada.

Este estudio profundiza en el ámbito de la gestión de la confianza en el contexto de las redes 6G, centrándose en la utilización de algoritmos de lógica difusa. Aprovechando metodologías avanzadas y dando prioridad a la confianza como elemento fundamental, El objetivo de este estudio es investigar formas de avanzar hacia un ecosistema 6G seguro y eficiente que proporcione servicios de alta calidad en diversas aplicaciones y entornos. A través de un análisis exhaustivo de los conceptos de confianza y de técnicas de evaluación que utilizan la lógica difusa en conjunto con otras tecnologías innovadoras como la inteligencia artificial y el blockchain, este estudio arroja luz sobre los beneficios potenciales y las implicaciones de integrar estas soluciones en escenarios del mundo real. Palabra clave: gestión de la confianza, difusa, 6G

En este trabajo presentamos un método para diseñar bocinas cónicas compactas y ultra cortas corregidas por lentes dieléctricas para sistemas de comunicaciones inalámbricos. Mostraremos algunos prototipos de bocinas acortadas trabajando a 60 GHz con una razonable directividad y bajas pérdidas de retorno en una ancha banda de frecuencias.

This paper describes the design of a broadbandmicrostrip antenna, which is fed by a differential microstrip

line. The designed antenna is made of two stacked patches excited trough a dog-bone shaped aperture by a short-circuited differential microstrip line. The short-circuited differential line is symmetrically located with respect to the aperture so that its differential mode is naturally excited, while its common-mode

is intrinsically rejected. The antenna design is based on an equivalent circuit which includes a second-order Chebyshev filter composed of two capacitively coupled LC parallel resonators. In order to carry out the analysis and measurement of the antenna, a two-port feeding mechanism is introduced involving a 180º hybrid in such a way that the differential-mode excites the first port, while the common-mode excites the second port. A prototype of the differential microstrip antenna has been fabricated and measured, and good agreement has been found

between simulations and experiments. For a center frequency of 5.5 GHz, the prototype shows a fractional bandwidth close to 35 %, an average gain of 6.5 dBi, and crosspolar levels below -20 dB.

An inverted-L monopole radiating element is proposed for phased arrays at the mm-wave band. Its radiation pattern is half-isotropic and is well-suited for mobile communications. The ideal inverted-L monopole is analyzed by assuming a sinusoidal current and initial design values for the lengths of its segments are found to obtain half-isotropic radiation. Results are contrasted with simulations using a commercial software. The scanning capabilities and coverage of an array of such elements is shown. The beam coverage of the proposed array is very high, covering almost the whole space with a directivity of 15 dBi or more by using just two arrays of 16 elements.

Multiple-input multiple-output (MIMO) technology has emerged as a highly promising solution for wireless communication, offering an opportunity to overcome the limitations of traffic capacity in high-speed broadband wireless network access. By utilizing multiple antennas at both the transmitting and receiving Sub-6GHz ends, the MIMO system enhances the efficiency and performance of wireless communication systems [1]. This work presents a comparison of the performance of two families of M-CRotationally Symmetrical MIMO antenna design approaches one based on the Magneto Electric (ME) dipole antenna and a second one based on the Circular Cavity principle intended for their use into advanced MIMO applications like Orthogonal Angular Momentum (OAM) and high capacity channels. A comparison of the relevant performance parameters in terms of frequency bandwidth (both input impedance S_ii and inter-port isolation S_ij) and radiation pattern are presented for the two Sub-6GHz prototypes.

En este artículo presentamos un nuevo sistema

inalámbrico de transferencia de energía de alta eficiencia para

implantes biomédicos. El sistema consta de una antena

implantable de doble banda, una antena de parche desmontable

y un rectificador doblador de tensión. El transmisor tiene un

ancho de banda de impedancia inferior a -10 dB desde 1,461

hasta 1,48 GHz. Por su parte, el receptor de doble banda tiene

unos anchos de banda de impedancia del 23,4% y el 16,5% a 915

MHz (el ISM industrial, científico y médico) y 1,47 GHz,

respectivamente. Se ha observado una buena concordancia entre

los resultados medidos en el interior de carne picada de cerdo y

de salmón. Por último, se ha desarrollado un rectificador

ultrapequeño de 10 x 9 𝐦𝐦𝟐 para integrarlo en el dispositivo

implantable para la transferencia inalámbrica de energía.

This communication introduces an antenna with frequency-dependent scanning capabilities specifically tailored for the automotive radar application with a fixed center frequency of 24 GHz. The preliminary antenna design ensures high efficiency and maintains a low profile despite its metallic composition. With dimensions of 11.25 cm × 6.25 cm × 1.25 cm, this compact and low-profile antenna exhibits fast scanning characteristics within a narrow bandwidth. Over a mere 5% bandwidth, it achieves scanning angles of 45 degrees (−25 degrees to +20 degrees). Despite the absence of experimental validation, the simulated results exhibit a directivity close to 22 dBi with 90% radiation efficiency, necessitating further validation through experimentation.

This paper proposes a methodology to extract the equivalent circuit of a broadband microstrip antenna consisting of two stacked patches fed through a resonant rectangular aperture by an open-ended microstrip line. The equivalent circuit includes three LC parallel resonators, out of which two are inductively coupled and two are capacitively coupled. In order to extract the equivalent circuit of the antenna, its simulated input impedance is fitted as a rational function, and the coefficients of the polynomials involved in the rational function are obtained by the least squares method. Once the rational function is known, the equivalent circuit parameters are derived in terms of the polynomial coefficients and subsequently optimized. A broadband microstrip antenna with center frequency of 8.79 GHz and fractional bandwidth around 45\% has been designed and its equivalent circuit has been obtained. Good agreement has been found between the frequency response of the optimized equivalent circuit and that of the antenna.

Existen multitud de ámbitos en los que es de especial importancia realizar una correcta caracterización acústica de materiales. Para llevar a cabo esta caracterización se pueden emplear diversos métodos, como el de cámara reverberante, cámara anecoica, o método de tubo de impedancia. Con el auge de las técnicas de impresión 3D se pueden conseguir diseños con geometrías y estructuras a la carta con prestaciones acústicas específicas, así como nuevos materiales con características acústicas propias no estudiadas hasta ahora. En este artículo se ha empleado el método del tubo de impedancias para medir el coeficiente de absorción y las pérdidas de trasmisión de una selección de muestras fabricadas mediante impresión 3D hechas en el termoplástico ASA, a fin de caracterizarlas acústicamente. Mediante este procedimiento, se han confrontado las diferencias en el comportamiento acústico entre muestras planas y muestras diseñadas mediante la denominada técnica QRD (Quadratic-Residue-Diffusor) con dos acabados (plano y en cuña) y para los primos p=7 y 11. Por otro lado, también se han comparado, mediante el mismo método, las diferencias existentes de absorción, trasmisión e impedancia acústica entre muestras basadas en fabricación aditiva de distintas densidades de impresión.

This paper presents a multicarrier modulation system with low complexity designed for wide-band underwater acoustic communications within the ultrasonic range (from

32 kHz to 128 kHz). Underwater Acoustic Communications (UAC) systems are recognized as one of the most challenging communication media in use today due to their temporal and frequency selectivity characteristics. This paper addresses the development of an OFDM (Orthogonal Frequency Division Multiplexing) system employing QPSK (Quadrature Phase Shift Keying) modulation. Paper describes the performance comparison between two methods of channel response estimation using pilots: time interpolation versus frequency interpolation. The system’s performance is evaluated using impulse responses obtained from shallow water measurements conducted in the Mediterranean Sea.

Automatic Speech Recognition (ASR) is emerging

as a crucial technology for voice recognition in future Extended

Reality (XR) and Metaverse applications, enabling natural in-

teractions with virtual and IoT objects. This paper evaluates

the performance of Microsoft HoloLens 2 microphone APIs

for sound acquisition, quality and noise cancellation in Mixed

Reality (MR) scenarios. Three APIs are assessed focusing on

sound quality, noise cancellation and speech filtering processes

using ASR metrics like Character Error Rate (CER) and Word

Error Rate (WER). The provided findings offer insights for MR

developers, emphasizing the importance of selecting the right

API to enhance sound quality and ASR model precision. This

highlights the significance of proper API selection for optimizing

MR applications.

This work outlines the synthesis procedure for the development of ladder acoustic wave (AW) filters with uniform electro-acoustic coupling. This approach prevents the need to include external components in a final filter configuration and therefore provides a simpler and valuable network from the application point of view. The paper presents the initial synthesis process and complements it with an iterative and formulated process to obtain a ladder network with prescribed electro-acoustic coupling. The process has been fully proved with a fabricated order 2 filter.