ABSTRACT. This paper presents field measurements of different beamforming mechanisms using a commercial 5G network. Beamforming enhances signal quality and capacity through directional transmission, and its effectiveness depends on factors like user position and feedback. We analyze Sounding Reference Signal (SRS)-based and codebook-based beamforming under real-world conditions. Results show SRS-based beamforming excels in mid-cell areas, while codebook-based performs better at the cell edge.

ABSTRACT. The performance of Vehicular Ad Hoc Networks (VANETs) is largely dependent on robust data propagation methods. This paper addresses the specific challenges of the Infrastructure-to-Vehicle (I2V) communication for a new Bus-based Services Advertisement (BSAD) Protocol. BSAD utilises the predefined routes of public buses to act as data units, disseminating service information from a fixed Road Side Unit (RSU). Employing a state-of-the-art simulation framework, this paper evaluates the performance of BSAD on a multi-lane highway, focusing on the effects of broadcast frequency and bus speed on propagation success. A key finding is that a transmission rate of 5/s ensures complete packet delivery to all buses, thereby resolving the issue of data loss in fast-moving environments, improving reliability and operational efficiency for I2V propagation.

ABSTRACT. This work investigates the application of the Mixed Discrete Fourier Transform (DMFT) formulation within the Split-Step Parabolic Equation (SSPE) method for millimeter-wave (mmW) propagation analysis. This numerical algorithm was validated using canonical cases to assess its applicability in mmW frequency bands. The case studies included comparisons with Two-Ray and Ray Tracing (RT) models. The results demonstrate that the DMFT-SSPE implementation provides accurate pathloss predictions, maintaining numerical stability and rapid convergence. These findings indicate that the proposed method is a promising tool for modeling high-frequency radio channels and supporting 5G network planning.

ABSTRACT. This paper reports initial measurements of LoRa signals downlinked from Starlink satellites operating in the 137-138 MHz Very High Frequency (VHF) band. These signals correspond to the Starlink VHF beacon, which uses a LoRa-based format derived from the Swarm SpaceBEE system (now integrated into SpaceX's infrastructure) for low-rate telemetry and tracking. Measurements were obtained over a five-month observation campaign, with valid data from three satellites received using a compact, low-cost ground station. Each decoded packet includes received signal strength indicator (RSSI), signal-to-noise ratio (SNR), and satellite geometry derived from public Two-Line Element (TLE) data. Successful receptions generally occurred for SNR above -10dB, while RSSI alone showed a weaker correlation with decoding success. Both metrics improved at higher elevation angles and decayed with slant range. Although limited in scope, these measurements provide the first empirical view of Starlink’s 137 MHz LoRa downlink and suggest that deploying additional tiny ground stations could support cross-site validation and improved modeling of VHF satellite-to-Earth LoRa links, which is relevant for emerging IoT satellite systems.

ABSTRACT. Non-invasive brain stimulation modulates neural activity by inducing E-fields. We extend a recently developed MATLAB-based cable solver for determining the response of a neuron cell to stimuli to incorporate E-field stimulation, thereby enabling its use to study the effects of electromagnetic brain stimulation. Simulations with Blue Brain Project model neurons show results consistent with the literature indicating that activation thresholds depend strongly on cell type and depth, with deeper pyramidal cells more sensitive. Incorporating realistic rat head conductivity further elevates thresholds, underscoring the role of tissue heterogeneity. This framework offers a transparent, accessible platform for studying neuron–field interactions.

ABSTRACT. This paper proposes a dual-band frequency selective surface (FSS) synthesized with a radial basis function (RBF) neural network. A convoluted unit cell was optimized to operate at the ISM (2.45 GHz) and UNII (5.5 GHz) bands. A database of simulated responses was used to train the RBF model, which achieved accurate parameter prediction with a root-mean-square error of 0.02. The fabricated prototype showed good agreement with simulations, exhibiting dual-band operation, polarization independence, and angular stability. The results confirm the effectiveness of ANN-based synthesis for rapid and efficient FSS design in wireless communication applications.

ABSTRACT. This paper presents an ultra-wideband (UWB) antenna in the millimeter-wave (mmWave) region designed for 5G applications. The proposed metasurface-based antenna consists of a 3 × 3 patch array modified with additional slots and extensions, fed through a coupling slot. This configuration allows redistributing the surface currents, thus improving the radiation performance over a wide frequency range. The antenna operates over a wide spectrum, offers a bandwidth ranging from 24.24 GHz to 30.71 GHz, representing a fractional bandwidth of more than 22%. In addition, it achieves a gain of 8.6 dB, positioning it as a highly efficient solution for UWB communication systems that demand high-speed data transmission and reception.

ABSTRACT. This work describes a structure that achieves simultaneous tri-band absorption and broadband polarization conversion in a single device. The unit cell consists of three square loops and a square patch with a diagonal split, printed on a grounded dielectric substrate and covered by a superstrate, both FR-4. The proposed design offers absorption peaks of 99.98%, 97.6% and 97.6% at frequencies of 1.87 GHz, 3.3 GHz and 4.8 GHz, respectively, while polarization conversion occurs in the Xband, from 8.22 to 9.26 GHz, with a polarization conversion rate above 90% across the entire band. Furthermore, the structure is compact, with dimensions of 0.1λ × 0.1λ (length and width) and a thickness equivalent to λ/50.12 at the lowest frequency of absorption.

ABSTRACT. This paper presents an optically transparent metasurface (OTMS) based on an indium tin oxide (ITO) split-ring resonators (SRRs) on a flexible substrate for precise wavefront manipulation. By only rotating the SRRs in five orientations, five distinct phase states are achieved at 14GHz. Two OTMS devices using this SRRs are demonstrated: beamsplitting and orbital angular momentum (OAM) mode generator. The devices achieve a ±38° beam split and successful OAM mode generation, highlighting the potential of transparent, flexible metasurfaces for next-generation communication technologies.

ABSTRACT. This paper presents a experimental validation for a PIN-diode-based reconfigurable metasurface (MTS) designed to dynamically control electromagnetic wave propagation. The MTS consists of an array of interconnected split-square-ring resonators (SSqRRs), enabling electronic beam-switching between two distinct spatial directions through controlled diode bias states. Experimental measurements demonstrate robust beam redirection at 5 GHz, with cross-talk (CT) exceeding 20 dB between the two propagation paths. The design demonstrates a compact and cost-effective platform for real-time reconfigurable beam control, suitable for wireless and sensing applications.

ABSTRACT. In this paper, we present the dispersion analysis of a dielectric strip grating using the MM-Bloch analysis. Aspects of how to implement the method for this type of structure are discussed.

ABSTRACT. Additive manufacturing techniques have generated interest in fully metallic conformal polarizers for space applications. While proof-of-concept designs can be produced with general-purpose design tools, specialized numerical methods are needed to accurately model these structures. We suggest using an ad-hoc Method of Moments that integrates analytical Green's functions for magnetic sources, which excite a radial transmission line in the presence of a metallic sphere.

ABSTRACT. This keynote talk presents emerging mission-critical antennas and propagation (AP) developments and applications combining concepts, techniques, and technologies of theoretical, computational, experimental, and applied electromagnetics (EM) with emerging interdisciplinary topics, with impacts on biomedical and sensing devices and systems. We present a quick overview of 75 years of research in computational electromagnetics (CEM) with an emphasis on current trends and future prospects, and specifically a synergistic combination of error estimation and control, adaptive refinement, and uncertainty quantification for CEM, which are essential for modern effective and reliable simulation-based design in mission-critical applications. The engineering applications include propagation modeling for smart underground mining; design of RF coils/antennas for next-generation high-field, high-frequency magnetic resonance imaging scanners; direct electromagnetic coupling system for orthopaedic fracture-healing diagnostics using external radio antenna sensors; and in-situ and remote-sensing measurements, modeling, and characterization of precipitation. In addition, we present recent advancements in the utilization of AI and machine learning in EM and AP, including data-enabled approach to predicting efficient macro basis functions for CEM, parametric antenna design for medical applications, specific absorption rate in human body predictions, and telemedicine orthopaedic diagnostic tools.

ABSTRACT. A compact circularly polarized antenna is presented for medical and wearable applications operating in the 2.45 GHz ISM band. Miniaturization is achieved through the use of an Al₂O₃ superstrate, four shorting pins, and 45° slots that control the surface currents and generate circular polarization. The antenna employs a coaxially fed circular patch and maintains an overall size of 0.32λg × 0.32λg (guided wavelength at 2.45 GHz). Stable performance is demonstrated in both free-space and on-body conditions, achieving an impedance bandwidth of 4.2% and an axial-ratio bandwidth of 4.6%. SAR values of 0.231 W/kg and 0.35 W/kg for 1-g and 10-g tissues remain well below IEEE/IEC safety limits. Owing to its compact structure, efficient CP radiation, and low SAR, the proposed design is suitable for wearable health-monitoring and body-centric wireless systems.

ABSTRACT. This paper presents the design, fabrication, and measurement of a deployable series-fed loop antenna array for a CubeSat 1U platform. Based on the baseline design in [1], the antenna was reimplemented on a flexible tape substrate and fabricated with thinner copper wire to enable a lightweight, foldable configuration. Since the tape introduces a frequency shift due to its effective permittivity, its dielectric properties were characterized, and both the antenna geometry and coupling network were redesigned to target 2.1575 GHz. The final prototype was optimized in CST Studio Suite and experimentally validated. Measurements showed good performance, in agreement with simulations for both reflection coefficient and gain.

ABSTRACT. This paper presents the design of a four-element antenna array implemented in Half Mode - Groove Gap Waveguide(HM-GGW) technology for Ka-band applications. Each radiating element consists of a slotted narrow-wall antenna, excited in phase by a 4-way power divider also realized in HM-GGW. The design process begins with the characterization of the unit cell to extract the propagation constant and coupling properties, which are then used to optimize a single element and the feeding network. The complete array is modeled and simulated using Ansys HFSS, showing high directivity and controlled side-lobelevel.

ABSTRACT. This work presents a 3D-printed dielectric resonator antenna (DRA) with a broadside symmetrical radiation pattern. The design features a cylindrical DRA centered at an operating frequency of 28 GHz, enclosed by a high-permittivity dielectric elliptical cavity that converts the inherently asymmetrical radiation pattern into a symmetrical one in the main planes. The feeding network consists of an aperture-coupled slot fed by a 50 Ω microstrip line through a vertical coaxial connector. Simulation results demonstrate proper impedance matching, a maximum gain of 9.5 dBi, and a symmetrical radiation pattern across the 26–30 GHz range.

ABSTRACT. This work presents the design of hybrid couplers in Half-Mode Groove Gap Waveguide technology as building blocks for the synthesis of beamforming matrices within the generalized joined coupler framework in the W-band. The process includes obtaining coupling and phase parameters through optimization, which are implemented in couplers and phase shifters based on HM-GGW. Simulation results confirm the feasibility of integrating these components into compact multibeam networks.

ABSTRACT. A compact coplanar waveguide (CPW)-based ultra-wideband (UWB) antenna is proposed. The design achieves an impedance bandwidth from 2.26 to 11 GHz within a compact footprint of 27 × 18 mm² on a 1.6-mm-thick substrate. A truncated and slotted radiating patch, together with a modified ground plane, is employed to realize wideband operation. The antenna is fabricated on an FR-4 substrate (εr = 4.4, tanδ = 0.025) and exhibits stable impedance matching and radiation performance across the entire UWB frequency range.

ABSTRACT. Overwater wireless links are strongly affected by specular reflections from the water surface, which can cause deep fading and received-power fluctuations. In tide-influenced links, water-level variations across the tidal cycle modify the propagation geometry and the associated reflection coefficient, giving rise to what is commonly referred to as tidal fading. This paper proposes an antenna height design strategy that leverages the pseudo-Brewster condition to mitigate reflection-induced fading across the tidal range. Simulations across multiple frequencies and distances show that the method reduces path-loss variance by more than an order of magnitude and limits the dynamic range to about 1–2 dB, with minimal impact on mean path loss, providing a practical guideline for reliable IoT and coastal communications.

ABSTRACT. Monthly variations of rain attenuation are crucial to be studied due its temporal and spatial variability. This paper presents monthly rainfall rate statistics derived from measurements collected at different sites in Cochabamba, Bolivia, and compares them with current ITU-R model, which originally is not explicitly recommended to be used on a monthly-basis. The comparison provides insights into the variability and accuracy of monthly modeling.

ABSTRACT. This work explores the application of AI to predict vehicle length and height for ISAC systems in 6G, using exclusively the RSS patterns generated by vehicular blockages in a 28 GHz LOS link. A total of 529 blockage events were processed, incorporating nonlinear label transformations and feature extraction based on the DWT combined with statistical, spectral, and temporal descriptors. Six regression models were evaluated, including MLP, Ridge regression, TCN, GRU, LightGBM, and XGBoost. LightGBM outperformed the other architectures, yielding MAEs of 9.6 cm for height and 49 cm for length. These results demonstrate the feasibility of power only vehicle sensing for future V2X networks with simplified infrastructure.

ABSTRACT. Pulsed electromagnetic fields have been used for cell electroporation in different contexts. The most used criteria for designing electroporation waveforms are usually the electric field peak amplitude and pulse duration. In this work, sinusoidal electromagnetic pulses of 48 kV/m and variable duration are proposed for controlling bacterial growth (E. coli) in drinking water. The number of pulses is increased to achieve the same energy density as in a commercial electroporator, allowing for the evaluation of the effectiveness of this waveform in the electroporation process.

ABSTRACT. This paper presents the validation of a novel impedance measurement bench based on an oscilloscope (OSC) designed for Near Field Communication Wireless Charging (NFC Charging) applications. The OSC bench is evaluated against the conventional Vector Network Analyzer (VNA) setup, which is the reference standard used by the NFC Forum and Wireless Power Consortium (WPC), as well as leading NFC solution providers. Measurement analyses compare accuracy, measurement range, and capability between the two benches. Results demonstrate that the OSC bench achieves comparable accuracy and reliability to the VNA, while offering a cost-effective and accessible alternative for high-power impedance and non-linearity measurements in NFC systems. This validation confirms the practical adoption of the OSC bench for antenna design and performance evaluation in NFC wireless charging.

ABSTRACT. This work presents the design, simulation, and experimental validation of a high-quality factor microwave sensor for measuring the relative permittivity of solid materials. The proposed sensor integrates an interdigital capacitor (IDC) into a rectangular microstrip patch antenna. The sensor achieved a quality factor of 440, a frequency detection resolution (FDR) of 62 MHz, and an average measurement error of only 0.07%. Numerical simulations and equivalent circuit modeling confirm the accuracy of the sensor’s behavior, while experimental measurements using five materials under test (MUTs) validate its practical performance.

ABSTRACT. Vehicular blockage significantly impacts 28 GHz links, often creating complex fading patterns within a single obstruction event. While overall blockage statistics are known, the internal temporal structure lacks characterization. This work analyzes the statistics of the number of shadowing events (SEs) occurring within individual blockage periods caused by vehicles, using empirical data. We find that low vehicles induce significantly more internal SEs than tall vehicles, with counts following Log-normal distributions. Correlation analysis reveals that the speed-normalized duration of the blockage positively correlates with the number of internal SEs only for low vehicles. For tall vehicles, this count appears to be independent of duration. These results suggest that vehicle geometry strongly influences the fine-grained fading dynamics, necessitating channel models that incorporate intra-blockage statistics.

ABSTRACT. This work presents the development and experimental validation of a microstrip-based sensor for volumetric estimation of fuel mixtures, specifically ethanol and gasoline, using microwave near-field sensing. The proposed device was designed to operate non-invasively and without direct contact with the sample, allowing the scattering analysis when the sensor interacts with solutions of different ethanol-gasoline concentrations. The sensor response was initially studied through numerical simulations using the Finite Element Method (FEM), and subsequently validated experimentally. The experimental data were employed for the training of an artificial neural network, responsible for correlating the sensor's responses with the volumetric estimation of the different mixtures. The experimental results confirm the potential of the proposed methodology for the fuel volumetric estimation, demonstrating an innovative, accurate, and efficient method for the analysis of ethanol-gasoline mixtures.

ABSTRACT. This work reports a 140 GHz channel measurement campaign in an urban street canyon (SC), supporting propagation modeling for 6G networks. Eighty-seven links between a rooftop BS and a street-level SU were analyzed under LOS and NLOS around-the-corner conditions. LOS results closely follow the Friis model (RMSE = 2.97 dB), while NLOS links exhibit a median additional loss due to propagation around the corner (CL) of 32.5 dB. The log-normal model provided an accurate fit for NLOS (RMSE = 3.7 dB, n = -6.5). These results highlight the corner loss at sub-THz frequencies and provide key parameters for 6G urban network design.

ABSTRACT. This article presents the design and analysis of a microstrip antenna with a photonic band gap (PBG) structure based on the quasiperiodic Penrose pattern. The antenna was designed on an FR4 substrate (εᵣ = 4.4) and uses air holes in the substrate to obtain better results in the antenna parameters. The use of a quasiperiodic PBG inspired by Penrose brought improvements in electric field concentration and surface current distribution, in addition to obtaining attenuation in the upper resonant modes.

ABSTRACT. Abstract—Breast cancer is a leading cause of mortality worldwide, necessitating effective, non-invasive early detection methods. This paper proposes a Radio Frequency (RF) detection system based on the analysis of scattering parameters (Sparameters) to identify permittivity variations associated with malignant tumors. A high-fidelity anthropomorphic breast phantom incorporating detailed ductal and lobular anatomy was simulated in the 1–8 GHz range. We evaluated the system’s sensitivity by introducing spherical tumor models of varying diameters (0.6 mm, 1 mm, and 5 mm). The results demonstrate a distinct correlation between tumor size and signal attenuation. Specifically, at the resonant frequency of 3.2 GHz, the transmission coefficient (S21) decreased from -35 dB for a 0.6 mm tumor to -47 dB for a 5 mm tumor. These findings confirm the feasibility of using RF simulations to detect sub-millimeter anomalies based on dielectric contrast, offering a theoretical foundation for future portable diagnostic devices. Index Terms—Microwave Imaging, Dielectric Permittivity, SParameters, Breast Cancer, CST Simulation.

ABSTRACT. Sparse antenna arrays have emerged as a powerful solution for direction-of-arrival (DOA) estimation, enabling large virtual apertures with a reduced number of physical sensors. This paper presents an extended and automated framework that integrates Python with CST Studio Suite for the electromagnetic design of Uniform Linear Arrays (ULA), Coprime Arrays, and Nested Arrays. Antenna elements and full array geometries are generated programmatically, allowing fast construction, parameter sweeping, and large-scale reproducibility. The resulting CST models are processed in Python, where the MUSIC algorithm is applied to evaluate angular resolution under noisy and multi-source conditions. Results show that sparse configurations outperform traditional ULAs, with the Nested array exhibiting the sharpest peaks and strongest robustness due to its hole-free difference coarray and superior degrees of freedom.

ABSTRACT. The use of unmanned aerial vehicles (UAVs) has enhanced the development of remote sensing systems for agricultural monitoring. This study presents a deep learning–based system for the early detection of foliar diseases in maize using aerial images captured with a drone. Three lightweight YOLO variants are employed: YOLOv8n, YOLOv8s, and YOLOv9c, selected for their efficiency and feasibility in embedded computing environments. The methodological workflow includes aerial acquisition, manual annotation, preprocessing, and training. In addition, aspects associated with the propagation of electromagnetic radiation in the visible range are considered, including acquisition geometry, footprint, leaf reflectance, and spectral variability. The qualitative results show that the system makes it possible to identify anomalous patterns on the leaves, demonstrating its potential for early monitoring in real environments.

ABSTRACT. In this paper, a new configuration of the MTK-LA is presented aiming to increase the antenna bandwidth. The initial design equations are provided. To verify the expected characteristics, a prototype operating at 0.93 GHz was designed, fabricated, and characterized, demonstrating good agreement between numerical and measured results. The achieved bandwidth of 50 MHz was approximately eight times greater than that of the original MTK-LA, which had a bandwidth of 7 MHz. This result indicates that the new configuration can be used to control the bandwidth of the MTK-LA.

ABSTRACT. This paper discusses the impact of discrepancies between datasheet specifications and measurement parameters of the substrate used to fabricate patch antennas, including dielectric constant, loss tangent, and substrate thickness. The design of several prototypes shows that incorporating measured substrate parameters into the design process yields the best agreement between the design and the prototype.

ABSTRACT. This manuscript proposes a hybrid antenna with filamentary and planar LPDA characteristics. The central axis is a flexible flat base that uses two layers of conductors and a layer of dielectric. The set of dipoles is aerially exhibited, and the thickness is considered for impedance matching. The prototype shows a size of 29.7×31.2×0.48 cm³ with a weight of 0.44 pounds. The performance, in terms of the realized gain, varies approximately between 3.8 and 8.0 dBi, which is a promising result compared to state-of-the-art antenna models of similar boom length, in the frequency band of digital TV service of interest, 470 MHz to 890 MHz.

ABSTRACT. In this article, an artificial neural network model using subclassing API was trained to predict the real and imaginary parts of the S parameters of stepped-impedance filters with low-pass response. The model was validated using the MAE (Mean Absolute Error) metric in the test data, with a result equal to 0.013, which is a good value. A simulated filter had its real and imaginary parts of the S parameters predicted, with good results.

ABSTRACT. A dual port antenna system is proposed which supports both the mmWave and sub-6 GHz frequency bands of 5G cellular systems. A high dielectric constant reduces the physical footprint of the antenna system making it suitable for vertical panel integration on smartphones. The mmWave antenna is a series fed microstrip patch array antenna which offers a wide impedance bandwidth of 50% ranging from 21 to 35 GHz. The sub-6 GHz antenna is a printed monopole which operates at 2.4 GHz and delivers an omni-directional radiation pattern. Mutual coupling is below 25 dB for both the bands.

ABSTRACT. This study presents a comprehensive evaluation of multiple path loss models using empirical measurements collected at the Pontifical Catholic University of Rio de Janeiro (PUC- Rio) at 5.8 GHz. The primary objective is to determine which model most accurately represents real-world propagation be- havior. The analysis covers classical deterministic models—such as the Free-Space Path Loss (FSPL), the Two-Ray model and its critical-distance and sinusoidal variants—and contrasts their performance with an artificial intelligence–based approach. By integrating the ADAM optimization algorithm, the proposed AI model achieved a remarkable improvement in prediction accuracy over conventional models, highlighting the potential of machine learning as a powerful tool for precise and adaptive path loss estimation in complex environments

ABSTRACT. This paper presents the implementation of closed-form formulas to determine the number of elements needed for the design of a cylindrical wraparound array. It is demonstrated that these formulations allow such an analysis with significantly reduced computational effort in comparison to full-wave-based commercial software. A comparison between numerical and simulated results showed the effectiveness of the method in providing this parameter for the case of an array designed for GPS L1 (1.575 GHz) conformed onto a cylinder with diameter equal to 1.46 m.

ABSTRACT. The growing adoption of nanosatellites has significantly expanded access to space-based experimentation and education. However, early-stage CubeSat design and mission conceptualization remain challenging for students and first-time developers because of fragmented tools and steep learning curves. This paper presents NanoSatPlay, an AI-enabled, browser-based platform that unifies CubeSat design, configuration, orbit visualization, and intelligent design guidance within a single interactive environment. The system integrates a visual component-based satellite designer, a real-time three-dimensional orbit simulator, and a generative AI assistant that provides subsystem-level feedback and contextual learning support. By lowering technical barriers and emphasizing visual and experiential learning, NanoSatPlay enables rapid prototyping, systems-level understanding, and effective STEM education. The architecture, core features, and educational benefits of the platform are discussed, demonstrating its potential to democratize nanosatellite engineering

ABSTRACT. This paper presents the design of a conformal matching circuit to efficiently couple a 50 Ω source with a textile-based rectenna operating in the 700-900 MHz band. Modeled on a textile substrate, the circuit's performance is evaluated with respect to various structural folds. The results demonstrate the design's viability and adaptability for future wearable rectenna applications.

ABSTRACT. This work presents a microwave system for measuring relative humidity in 14 cm-thick hollow concrete blocks, aiming to establish a technique for structural integrity monitoring. Five block samples were selected for analysis, with a frequency-selective surface (FSS) employed as the sensing element. Two antenna arrays were designed to capture the frequency responses of the blocks combined with the FSS under different humidity levels. The results demonstrate a strong correlation between frequency variation and relative humidity. Numerical processing and statistical analysis enabled the derivation of a second-order function that models the relationship between resonance frequency and relative humidity. A quadratic regression was performed, yielding a function that satisfies the requirements of the proposed study across the full range of 0–100% relative humidity.

ABSTRACT. This study proposes a wireless power transfer (WPT) system based on inductive coupling for powering implantable medical devices (IMDs). The system operates at 403 MHz within the Medical Implant Communication Service (MICS) band. It consists of two resonators utilizing split-ring loops geometry. The transmitter and receiver feature compact dimensions of 25 mm x 25 mm x 1.52 mm and 14 mm x 14 mm x 1.27 mm, respectively. These are among the smallest dimensions reported for resonators based on planar split-ring loop geometry. Electromagnetic (EM) simulations were performed to optimize the geometry for maximum efficiency while maintaining reduced dimensions transfer distance. A measured power transfer efficiency (PTE) of 16.58 % is achieved at a transfer distance of 12.0 mm. According to numerical analyzes results, the maximum received power, limited by specific absorption rate (SAR) regulations, reaches 105.5 mW at 8 mm and 29.44 mW at 12 mm.

ABSTRACT. This paper presents an experimental electromagnetic characterization of a CFRP-foam-CFRP sandwich panel representative of UAV structural components, as a preliminary step toward microwave nondestructive testing (NDT). Free-space S11 and S21 measurements from 0.8-8GHz were obtained under multiple antenna-panel configurations using broadband horn antennas and a vector network analyzer. The results show strong attenuation above 3-4GHz due to the conductive CFRP skins, whereas the 0.8-4GHz band preserves measurable transmission and stable phase information suitable for probing the dielectric core. By comparing free-space and through-panel responses, the frequency-dependent phase behavior and excess delay were extracted. The analysis identifies the low-GHz region as the operational band for microwave NDT and supports the feasibility of future imaging approaches in multilayer composite structures used in UAV and aerospace applications.

ABSTRACT. This article introduces an antenna architecture capable of synthesizing arbitrary radiation nulls for interference mitigation. The design consists of a microstrip patch surrounded by four monopoles, oriented such that their radiation minima aligned with the patch maximum direction. Adaptive null formation is achieved by weighting the monopole excitations over user-defined angular sectors, with compatibility for passive network implementations. Full-wave simulations validate the null-steering capability and confirm minimal degradation of the main beam.

ABSTRACT. This paper presents the design, simulation, and implementation of an S-band (2.25 GHz) circularly polarized microstrip antenna for 3U CubeSat platforms. Addressing strict bus constraints of 92 × 92 mm and the LEO thermal requirements of the LEOpar mission, we propose a square patch with truncated corners on a custom inverted-U Rogers TMM4 substrate. Simulation results show a strongly matched resonance (S11 < −24 dB) and a 43.6 MHz circular polarization bandwidth. Validation confirmed the radiation pattern and topology performance, with polarization deviations due to fabrication tolerances.

ABSTRACT. This work presents a systematic methodology for designing single-ring metamaterial absorbers at specific resonant frequency in the GHz range with high absorption. The approach combines analytical modeling with a parametric full-wave study, performed in CST®, to characterize the influence of ring geometry, substrate properties, and unit-cell scaling on the resonant response and absorption. Based on these results, a step-by-step design procedure is proposed and validated through twelve case studies (1–50 GHz) simulated in CST®, showing strong agreement between predicted and simulated behaviors.

ABSTRACT. The objective of this study is to parametrically analyze the insertion of SETR (Split Equilateral Ring Resonator) structures in microstrip antennas with a circular patch in order to form DGS (Defected Ground Structures). The analysis of the radiation parameters of the simulated and fabricated variant antennas showed shifts in the resonance frequency to the left of the reference, as well as changes in bandwidth and reflection coefficient.

ABSTRACT. This paper proposes an extension of the spatial directivity map of the log-periodic dipole array (LPDA) antenna to a three-dimensional visualization of the boom length map. This contribution is unique because the directivity can be estimated outside of the contours following a minimal spatial path of boom length. Such mapping can be useful for the miniaturization of the LPDA structure. A new definition of spatial density for mapping is introduced in the digital TV band from 470 MHz to 890 MHz.

ABSTRACT. There is a very high demand for high-throughput, innovative beam-steering antenna solutions for wireless and satellite communication applications. In the last decade, beam-steering antennas have seen tremendous progress, primarily due to the maturity of silicon beamforming chipsets, multilayer printed circuit boards, and 3D printing technologies. This talk will provide an overview of various beam steering antenna mechanisms and basic antenna array theory, with a focus on design, practical implementation, and future development. One of the key technologies discussed will be the emerging flat-panel phased array antennas used in wireless and satellite communications. The presentation will examine electronic beam steering using beamforming networks and commercially available beamforming integrated circuits (BFIC) chips. Examples of flat-panel phased-array antennas featuring dual linear, dual circular, and polarization-reconfigurable designs will be presented. Additionally, an all-metal radiating-element-based phased-array antenna, in which the radiating element also serves as a heat sink and incorporates BFICs in its beamforming network, will be highlighted. During these discussions, the challenges and roles of silicon BFICs, multilayered printed circuit board (PCB) fabrication, RF component assembly, beam forming algorithms, and 3D dielectric and metal printing in antenna array designs will be explored. The presentation will briefly touch on antenna characterization techniques and the associated measurement challenges. Moreover, the talk will emphasize the importance of data-throughput testing of Ka-band flat-panel phased-array antennas, both in a laboratory environment and over-the-air (OTA) across a 1 km link between two buildings at San Diego State University. It will also cover data-throughput testing of a dual-circularly polarized Ka-band flat-panel phased array on a payload aboard a high-altitude balloon (HAB) at an altitude of approximately 100,000 ft.

ABSTRACT. We present the design and simulation of a Mikaelian-type GRIN lens, selected for its simple geometry, low aberrations, flat interface, and inherent beam-steering capability. The lens enables two-dimensional beam scanning through lateral feed displacement, offering a passive and low-complexity alternative to electronically phased arrays. Its electromagnetic performance is evaluated using a volumetric integral-equation (VIE) algorithm, which significantly reduces simulation time while maintaining full-wave accuracy. Far-field results validate key performance metrics such as directivity and aperture efficiency, demonstrating the potential of the proposed approach for advanced beam-steering applications.

ABSTRACT. This paper presents a non-invasive bottle inspection system utilizing a compact Vivaldi antenna for microwave imaging. The proposed system integrates antennas operating from 2.4 to 17.7 GHz into a conveyor-based production line. Through full-wave electromagnetic simulations, the system's performance is evaluated for detecting undesirable objects within a glass jar, varying in size, quantity, and position. The delay and sum method is utilized to reconstruct the images. The results successfully demonstrate the detection of a 0.4 mm polyethylene terephthalate object embedded within water. Analysis of S-parameters and reconstructed images confirms the potential of this microwave imaging approach for high-sensitivity, non-destructive food quality control.

ABSTRACT. This paper aims at investigating the advantages of a rigid coaxial-line leaky-wave antenna possessing 4-fold screw symmetry operating in linear polarization, compared with its conventional counterpart. Screw symmetric periodic slots are cut on the outer conductor of the cable leading to radiation through the n=-1 Floquet harmonic in the visible region. It is shown that, due to the intrinsic absence of coupling between the interested oppositely directed Floquet harmonics, the screw-symmetric LWA completely suppress the open-stopband at the broadside frequency, while the conventional counterpart does not.

ABSTRACT. This paper presents a novel Direction Finding technique by Time Modulated Arrays for multiple correlated signals. The method is based on the comparison between the obtained harmonics data from the output of the array, with a Look Up Table made of pre-computed values. A simulation of a concentric-rings array consisting of three rings is conducted to validate the proposed method. The resulting spatial spectrum demonstrates that the proposed method can successfully estimate the DoA of two correlated sources.

ABSTRACT. This work presents a compact, reconfigurable filtenna for 5G sub-6 GHz (from 705 to 773 MHz, and from 3.3 to 3.7 GHz) and UWB applications (from 690 MHz to 6 GHz). The FR4-based design integrates a bio-inspired, water lily-shaped monopole with a 3.5 GHz defected ground structure (DGS) filter and a 700 MHz interdigital filter. A PIN diode circuit selects the operating mode. The structure was simulated and then prototyped. Measurements validated the 5G narrowband modes. Despite fabrication-related deviations in the UWB results, the design is a viable and promising miniaturized solution for modern 5G devices.

ABSTRACT. In this work, we propose a co-design strategy for aperture sharing of a reflector antenna, operating at 28 GHz and a patch antenna, operating at 3.5 GHz. We mitigate the undesired effects of aperture sharing by shaping the patch antenna as a parabolic reflector. Furthermore, we fix the beam tilt caused by the orientation of the patch by creating a phase shift between the two radiating apertures of the patch. The effectiveness of the design is demonstrated in simulations.

ABSTRACT. This article presents the design of a 4x4 Butler matrix at 20 GHz using RGW technology. The main idea is to build the design using additive printing. The matrix has an insertion loss of 0.55 dB in a 2 GHz bandwidth, and the return losses are better than 24 dB over the entire bandwidth. The phase difference between adjacent ports has a maximum dispersion of 4 degrees. The final prototype will has 71 x 55 mm.

ABSTRACT. Radio Access Networks (RAN) moving toward sixth generation (6G) systems rely on Base Transceiver Station (BTS) antennas implementing Multiple Input Multiple Output (MIMO) and Massive MIMO (M--MIMO). Such arrays require models and bounds that explicitly account for mutual coupling, mismatch, polarization, and spatial selectivity at the cell level. Building on a recent framework that linked the \emph{average maximum gain} (AMG) to a correlation matrix of embedded element patterns (EEPs), this work extends the formulation to \emph{average maximum directivity} (AMD). We prove that AMD within a given angular region (\emph{cell}) admits a compact trace form involving the inverse of the efficiency correlation matrix (ECM) and the cell correlation matrix (CCM). The result leads to a matrix---termed the \emph{minimum spill-over matrix} (MSM)---whose eigenstructure directly furnishes patterns that maximize in-cell directivity while limiting out-of-cell radiation. Moreover, by enclosing the array in a minimum volume and invoking equivalent current representations, an upper bound to AMD is derived in terms of the electromagnetic degrees of freedom (DoF), thus providing geometry-dependent physical limits for any antenna inside the same box. These findings supply actionable guidance for array design and evaluation in future BTS deployments.

ABSTRACT. Modern industrial sectors—including communications, automotive, aerospace, and defence—depend on reliable antenna performance to deliver high‑quality systems. Designing and optimizing advanced antenna technologies, such as large phased arrays and integrated cabin antennas, presents formidable challenges because of their physical size and strong coupling to surrounding structures. Full‑wave 3‑D EM solvers can predict S‑parameters, radiation patterns, and field distributions, but the associated compute time and memory requirements often become a bottleneck. Modern antenna design requires efficient, high‑throughput numerical tools that retain full‑wave accuracy while drastically reducing simulation time. Such tools enable designers to evaluate complete antenna geometries without resorting to iterative hand‑tuned models, thus accelerating the entire development cycle. A key enabler is the use of Antenna Digital Twins (ADT), virtual replicas derived from either simulated field recordings of a simulation model or from measured near‑field data of a manufactured antenna. An ADT encapsulates the antenna’s radiation behaviour in a compact surface‑current model, allowing rapid assessment of its performance in any environment. Engineers can therefore place, orient, and assess antennas in vehicles, aircraft, and other platforms on the fly, without detailed knowledge of the underlying geometry. Moreover, by coupling the ADT with a surrounding‑structure model, one can predict real‑world interactions such as multipath and blockage, and optimise antenna positions for optimal field coverage. ADT‑based numerical compliance testing offers a powerful alternative to time‑consuming robotic measurements under radio‑frequency exposure regulations (e.g., SAR and EMF limits), thereby enabling virtual certification of safety and compliance. Looking ahead, the integration of artificial‑intelligence (AI) and machine‑learning (ML) algorithms directly into the full‑wave solver pipeline promises a further leap in efficiency. AI driven modelling accelerates iterative sweeps, and optimisation algorithms are automated, expanding the design space and shortening the path to optimal solutions. By combining fast, accurate full‑wave solvers, ADT‑based environment co‑design, and AI‑augmented optimisation, industries can perform high‑confidence performance prediction with minimal physical prototypes. The resulting integrated methodology delivers reliable, high‑performance, and cost‑effective antenna solutions that satisfy the stringent demands of today’s and tomorrow’s applications.

ABSTRACT. This work investigates the limits on the microstrip patch antenna miniaturization using the Sierpinski Carpet fractal. A square patch and its first four fractal iterations were optimized at 2.45 GHz through full-wave simulations. Fractal geometry increases the electrical path length, achieving up to 21% area reduction with limited impact on impedance matching and radiation. Higher fractal iterations, however, add unnecessary complexity, reducing bandwidth and gain.

ABSTRACT. Free-space optical (FSO) communication enables high-throughput, rapidly deployable links, yet its availability is limited by weather-induced attenuation. We propose a simple method to estimate the combined effect of fog and rain using ITU-R rainfall-rate statistics and long-term visibility data. The resulting attenuation CCDF is evaluated through a link-budget equation to compute the maximum path length for a target availability. Results show that in regions where fog occurrence is negligible, the achievable path length exceeds 1 km at 99.95% availability, whereas fog-dominated areas remain restricted to only a few hundred meters.

ABSTRACT. A compact two-port MIMO antenna is presented for millimeter-wave 5G communication. Each antenna element consists of a rectangular patch with an extended edge arm, enabling a wide impedance bandwidth of 4 GHz (36–40 GHz). The antenna is designed using a Rogers RT-5880 substrate (relative permittivity εᵣ = 2.2, thickness h = 0.8 mm, and loss tangent tanδ = 0.0009). The two-element MIMO configuration achieves inter-port isolation greater than 25 dB and a peak gain of 8 dBi at 38 GHz. Comprehensive performance evaluation is carried out, including S-parameters, isolation, radiation characteristics, gain, envelope correlation coefficient (ECC), and diversity gain (DG). The results demonstrate robust wideband operation and effective MIMO diversity performance, confirming that the proposed antenna is a suitable candidate for 5G millimeter-wave applications.

ABSTRACT. The design, simulation and analysis of a multi-frequency planar monopole antenna and its scalable arrays for modern communication applications are proposed. The base structure consists of a rectangular patch with microstrip feed, modified by incorporating four identical arc slots at its corners, and manufactured on an FR4 substrate (Er = 4.4). Based on this basic design, linear arrays of 2, 4, and 6 elements are developed, fed by an optimized distribution network from a single port. Simulation results in ANSYS HFSS reveal that the single-element configuration offers the highest bandwidth (180 MHz) with a quasi-omnidirectional radiation pattern. In contrast, designs with a higher number of elements show a significant improvement in impedance matching, reaching values of up to -59.36 dB in the case of two patches, along with more pronounced directivity. A key finding is the multifrequency behavior in the arrays, particularly in the four-element configuration, which exhibits additional stable resonances.

ABSTRACT. The realization of high-gain phased arrays for 6G D-band (110–170 GHz) communication is severely hindered by mutual coupling between closely spaced antenna elements. This paper investigates the use of a Complementary Metamaterial (CMM) structure integrated into the ground plane to suppress surface waves and enhance isolation in a D-band array environment. The CMM, designed as a periodic arrangement of Complementary Split-ring Resonators (CSRRs), acts as a bandstop filter for the surface waves responsible for coupling. Simulation results demonstrate a significant reduction in mutual coupling by 35 dB and an improvement in the array's overall radiation efficiency and scan performance. This technique is crucial for enabling the dense, high-performance D-band array integration necessary for terabit-per-second links.

ABSTRACT. This work presents a preliminary study and original proposal of circular microstrip patch antennas design based on the Circular Firat Fractal. The model proposes a consecutive reduction of reference radius and structure removal, presenting an outer radius reduction circle, which we named Firat Outer Model. A regular circular reference antenna was designed, and three iterations of the Firat Outer Model were applied. Then, the fractal antennas were redesigned to match the resonant frequency of the reference antenna. Reflection coefficient and miniaturization factors are evaluated by simulations and measurements. The results show the good performance of the model regarding miniaturization, with the area patch reduction of 64.89% at second iteration, with a difference between measured and simulated resonance frequency of 1.76%.

ABSTRACT. This paper presents the design and experimental validation of a 2 × 2 patch antenna array for ground-to-ground wireless power transmission at 2.4 GHz. The antenna, implemented on a Rogers RO4725JXR substrate, was optimized in CST Microwave Studio SuiteTM for impedance matching, gain, and radiation efficiency. Measurements show a minimum reflection coefficient of −38.32 dB at 2.425 GHz and a −10 dB bandwidth of 33 MHz, validating the agreement with simulations.

ABSTRACT. In this study, two nested inner and outer loops form a new dual band frequency selective surface (FSS) architecture. Both the square-framed outer ring and the star-shaped inner ring have independently adjustable frequencies. The size of single unit cell is taken as 4x4x0.5mm3 and a 4x4 array has been taken which has dimensions of 16x 16x0.5mm3. The use of a star shaped geometry allows for compactness while ensuring angular stability and polarization insensitivity. The outer square frame enhances structural stability and provides additional tuning flexibility for resonance frequency control. The proposed structure obtained dual passband at 15GHz and 28GHz and a stopband at 22GHz between the two passbands which allows selective use of frequencies, improving the spectral efficiency of the system. This work enables simultaneous transmission of two specific frequency bands while blocking another undesired band and useful for multi band operation with interference mitigation. Equivalent Circuit Model is analyzed and verified for the proposed star looped FSS design. For both TE and TM modes, it can attain stable resonance around center frequencies of 15 GHz and 28.6 GHz with an angular incidence of 0° to 80°.

ABSTRACT. A novel perfect metamaterial absorber, including double Gielis-generated resonators into an E-shaped fractal structure, has been numerically investigated. The absorber performance was evaluated over a frequency range of 1-7 GHz and compared to a similar structure without the fractal structure. The optimization approach produced a compact resonator with dimensions of 30 × 30 mm. The results reveal that this structure has absorption efficiencies of 84.6, 78.97, and 96.4% in the first, second, and third frequency bands, respectively. Also, other characteristic parameters were evaluated. demonstrating its suitability for electromagnetic energy harvesting.

ABSTRACT. A comparative analysis of three new bio-inspired antenna models applied to sensing and dielectric characterization of materials is presented. The Interdigital Capacitor (IDC) and Complementary Square Split-ring Resonator (CSSRR) geometries are used within the reference model for comparative sensitivity study and analysis. The frequency response of the proposed models was investigated. Antenna/sensor models with dimensions of 70×70×1.57 mm were constructed and subjected to experimental measurements, which validated their design, with the CSSRR model being the most sensitive. In general, the proposed sensor models demonstrate a good level of accuracy in the dielectric characterization process of materials.

ABSTRACT. This work aims to do a parametric analysis an antenna initially designed to operate in the S band, between 2 and 4 GHz, with the insertion of SETR (Split Equilateral Triangle Resonator) metamaterial structures in the ground plane forming DGS (Defected Ground Structures), in order to verify the influence of these changes on the antenna radiation parameters. The purpose is to make comparisons between the modified antennas and a reference antenna. Changes in the resonance frequency, bandwidth and reflection coefficient of the antennas were demonstrated.

ABSTRACT. This paper presents two Frequency Selective Surfaces (FSSs) based on square loops, designed to operate at 3.5 GHz, as band-stop and band-pass filters for 5G-systems applications. The structures were analyzed through simulations using the Ansys HFSS EM tool, and validated experimentally. The results conclude that the band-stop FSS provides efficient attenuation, showing to be a promising strategy for electromagnetic shielding applications, while the band-pass FSS exhibits high transmission, both at 3.5 GHz, demonstrating potential for applications focused on the enhancement of the smart antennas gain control.

ABSTRACT. Compact microstrip sensors are essential for various applications in the X-band (8–12 GHz), such as radar and communications. This work presents the design, simulation, and experimental characterization of a new resonant sensor based on a concentric hexagonal ring architecture that follows the matryoshka nesting concept. This topology aims to optimize the compactness and quality factor within the operating band. The sensor was designed to operate around 10 GHz. After simulation, the structure was fabricated on a substrate and subjected to rigorous measurements. The experimental results of the S11 parameters show excellent agreement with the simulated data, validating the design methodology. Specifically, the measured resonant frequency presented a variation of only ≈ 0, 1% relative to the simulated frequency, confirming the effectiveness of the approach for the development of compact, high-performance, and low-cost microwave sensors.

ABSTRACT. This study aims to present the development of a decision algorithm applied to a compact antenna with multiband characteristic. The proposed structure will be simulated using the commercial software HFSS, where the reconfiguration mechanism is based on the switching of four PIN diodes arranged on a selective surface that will be used as a superstrate in the final device. Using the simulated results of parameter S11, a decision algorithm will be developed which, based on the desired resonance frequency and within the selection criterion used (S11 module and relative error), will return the optimal combination of the state of the four diodes (on or off). All simulated results will be discussed. The development of the algorithm, as well as the selection criteria for its greater effectiveness, is explained throughout the work. Different alternative algorithms are also explored through sequential and interval search strategies.

ABSTRACT. This paper presents a meander-optimized dipole antenna designed for LoRa technology and for use in tracking and telemetry using small devices. The research includes design, antenna simulation, and the corresponding simulation results.

ABSTRACT. This work presents the design of an integrated rectangular patch antenna with a stepped-impedance low-pass filter for RF energy harvesting at 2.45 GHz. The structure was implemented on an FR-4 substrate and simulated in CST Microwave Studio. After optimization, the integrated structure achieved excellent performance with |S11| = −41.6 dB and realized gain of 3 dBi at 2.45 GHz. The results indicate that the tuned design improves impedance matching and performance, making it suitable for compact RF harvesting applications.

ABSTRACT. Radio Environment Maps (REMs) provide a structured way to represent spatial signal conditions and are increasingly used to support smarter network planning and optimization. In this work, we evaluate an open-source testbed and apply Machine Learning (ML) methods to generate indoor REMs for both uplink and downlink scenarios. The study relies on a 5G telco-cloud platform that enables scalable data gathering and processing suited to real indoor deployments. After running the measurement data through some ML models and checking their mean squared error (MSE) performance, we observed low error values, indicating that the coverage estimates are trustworthy, especially regarding signal quality classification.

ABSTRACT. This work presents the design and simulation of an Ultra-Wideband Vivaldi antenna for a breast cancer detection system. This design is intended to be employed in a synthetic array setup, fed by a Software-Defined Radio device operating as a portable Vector Network Analyzer. The antenna was simulated using the CST Studio Suite\textsuperscript{\textregistered}, in a 1.57 mm Rogers\textsuperscript{TM} 4003C substrate thickness and 0.035 mm copper thickness, with final dimensions of 63.9 mm width x 100.9 mm length. The simulation results show an operational bandwidth of 24 GHz for $S_{11}$ below -10 dB. Given that the system is expected to enter clinical tests in 2026, the Specific Absorption Rate was simulated for a maximum output power of 200 mW with a result of 1.98 W/kg, below the 2 W/kg limit defined by IEEE Standard for Safety Levels.

ABSTRACT. This work presents the design of a compact 1:8 stripline power divider operating at 16.42 GHz. A T-junction topology was implemented on a multilayer substrate and optimized for amplitude and phase balance. In the initial simulations, a degradation was observed due to parasitic coupling and undesired mode propagation. To address this issue, the use of via fences connecting the ground planes was investigated. The optimized configuration, using a via spacing of one twentieth of the free-space wavelength, significantly improved field confinement, reduced phase imbalance, and achieved an insertion loss of -10.7 dB. The results demonstrate the effectiveness of via-fence integration in improving the performance of high-frequency stripline power dividers.

ABSTRACT. This work presents a cost-effective multiband microstrip antenna on FR4 for 5G and millimeter-wave applications. The design incorporates a CSRR-based Defected Ground Structure (DGS) to enhance impedance matching and generate additional resonances. The fabricated prototype achieved resonances at approximately 15 GHz, 29 GHz, and 34–36 GHz. Simulated gain reached about 2.7 dBi at 14.4 GHz, confirming suitability for K-band and millimeter-wave applications. Both simulations and measurements exhibit good agreement across key frequency bands, with minor shifts attributed to fabrication tolerances and substrate losses. The proposed antenna offers practical performance for next-generation wireless systems while maintaining low cost.

ABSTRACT. A modified coupled-line bandpass filter for Bluetooth band is presented. The proposed squared geometry preserves the coupling behavior of the classical parallel configuration while significantly reducing physical area. Owing to additional parasitic capacitive interactions, the structure exhibits inherent dielectric sensitivity without requiring any modification to its filtering layout. The prototype, fabricated on FR-4, demonstrates a measured 2.33GHz - 2.45GHz passband and a 2.87% shift between simulated and measured frequencies. A maximum sensibility of 5.5% was observed. Experiments using FR4, ABS, and dry sand confirm the capability of the device to perform dual bandpass filtering and dielectric characterization.

ABSTRACT. This paper presents a machine learning-based framework to classify the reflection coefficient (|S11|) of pixelated microstrip patch antennas as either below or above −10 dB.The antenna geometry is modeled as a 7 × 5 binary matrix of removable pixels, enabling a highly flexible design space. A dataset of 7,995 antenna configurations was generated through full-wave FEM simulations in Ansys HFSS and automated using the PyAEDT Python interface. A Multi-Layer Perceptron (MLP) was trained across the nine evaluated frequencies 1–9 GHz and achieved f1-scores exceeding 82% for all cases. The proposed method significantly reduces the computational cost associated with traditional full-wave optimization and provides a fast, datadriven tool for the design of pixelated microstrip antennas.

ABSTRACT. This paper investigates a low-cost 77-80~GHz FMCW millimeter-wave radar workflow for short-range forest canopy-height estimation. Radar echoes collected along linear trajectories in front of real trees are processed with a standard FMCW chain (range FFT, log-magnitude, smoothing, and CFAR) to generate a point cloud and a simple ground profile. Unsupervised clustering (DBSCAN, OPTICS, and Mean Shift) is then used to isolate canopy returns and estimate per-tree height as the difference between the canopy envelope and the ground surface. Experiments on three trees (3.36~m - 3.45~m) show that DBSCAN and OPTICS achieve errors of about 0.2~m - 0.3~m for two trees, while Mean Shift tends to merge nearby crowns and yields a larger error (0.6~m). These results suggest that FMCW mmWave radar combined with clustering can provide canopy-height estimates within a few decimeters for local forest monitoring when airborne LiDAR is impractical.

ABSTRACT. The design of microwave patch antennas is a key area in the development of radio frequency sensors for agricultural applications. This project focuses on the design, simulation, and construction of a pair of microwave patch antennas optimized to characterize soil properties, such as salinity, moisture, and fertility. The proposed system will utilize these antennas—one for transmitting and one for receiving—integrated with a software-defined radio (SDR) platform like the USRP B200mini and GNU Radio. The antennas will be designed to operate at a specific frequency that maximizes penetration and sensitivity to dielectric variations in the soil. By measuring the attenuation and phase shift of the microwave signal traveling through the ground between the two antennas, it is possible to infer its composition in real-time. The objective is to develop a portable instrument, thanks to an efficient antenna design, provides farmers with accurate measurements to optimize irrigation, fertilization, and improve overall crop management.

ABSTRACT. This paper aims to evaluate the accuracy of Path Loss mathematical models using measurements taken at the Pontifícia Universidade Católica do Rio de Janeiro - PUC-Rio by comparing them with theoretical models such as the CI (Close-In) model and the Alpha-Beta model. Outdoor measurements were conducted with the transmitter installed on the Leme building at the PUC-Rio campus in Brazil. In total, 23 reception points were evaluated for 27-29 GHz frequencies. Afterward, Path Loss was plotted as a function of distance for both theoretical models and empirical data. Finally, Root Mean Square Error (RMSE) was calculated to assess the efficiency of theoretical models regarding empirical measures.

ABSTRACT. Radio Frequency Interference (RFI) from Global Navigation Satellite Systems (GNSS) is an increasing concern for radio astronomy, requiring continuous monitoring and reliable identification tools. This work presents preliminary results toward a GNSS satellite identification system that integrates radio astronomy instrumentation with the GNSSVis analysis pipeline. Observations near Campina Grande–PB, Brazil, using the Uirapuru radiotelescope covered the 0.98–1.30 GHz band, where signals from GPS, Galileo, BeiDou, and GLONASS are routinely detected. The acquired spectra were processed with GNSSVis to correlate radio features with satellite ephemerides, enabling synchronized visualization of satellite passes and RFI signatures. These results demonstrate the feasibility of the approach and lay the groundwork for a more comprehensive GNSS detection and mitigation system.

ABSTRACT. The current 5G mobile communication systems and the next generation 6G are especially affected by the wave propagation direction and multipath phenomena as the operation frequency is becoming higher. In this context, efficient methods to accurately measure the Angle of Arrival of a signal component is important to develop these technologies. This paper presents a novel method for enhanced AoA retrieval from high resolution channel impulse response. Machine Learning techniques are expected to be applied.

ABSTRACT. This paper presents an extended formulation of the Volume Filament Method for computing the impedance of printed coils operating at low frequencies under metallic shielding. The approach discretizes both the conductor and the shielding core into reduced-cross-section filaments, from which resistance, self- and mutual-inductance matrices are built, enabling the computation of current distribution and total impedance. Unlike conventional approximations, the method considers skin and proximity effects as well as magnetic backscattering through filament coupling, yet remains computationally lighter than full-wave techniques such as FEM. Validation was performed on a planar copper coil on FR-4 with an aluminum core, showing strong agreement with CST® simulations across the evaluated band, confirming accuracy in AC resistance and inductance prediction under shielding. Thus, the formulation proves to be an effective and efficient tool for analyzing, designing, and optimizing wireless power transfer systems using shielded printed coils.

ABSTRACT. This work presents a third-order local time stepping (LTS) method along with an efficient imposition source strategy applied to the discontinuous Galerkin time domain (DGTD) method in order to improve the time execution without compromise the precision. This formulation was applied to solve a complex multi-scale electromagnetic (EM) scattering problem. Numerical results showed that the proposed method maintain the precision of the standard DGTD with global time stepping (GTS) and reduced the time execution by about 80 %.

ABSTRACT. In this work, a reconfigurable middle stub filter is proposed. The filter was integrated on the transmission line of a monopole antenna enhanced with a CSRR structure for applications in ISM band and 5G. The work focusses on reconfigurability modeling and the reflection coefficient performance of the antenna (or filtenna) in four different switching states. The simulated results show that the switching configuration provides the control of the 3.5 GHz band, enabling and filtering according to the switching conditions 11 and 10, respectively, maintaining the 2.45 GHz band enabled with good impedance matching.

ABSTRACT. This paper presents the design, simulation, and implementation of a circularly polarized Quadrifilar Helix Antenna (QHA) as a passive solution to mitigate electromagnetic interference (jamming) in GNSS systems. The study aims to enhance the reception of GPS L1 signals (1.575 GHz) through an optimized right-hand circularly polarized (RHCP) antenna and to evaluate its performance against a conventional linearly polarized patch antenna. The analysis focuses on the Carrier-to-Noise Density Ratio (C/No), which reflects the quality of the received signal. To validate the proposed design, comprehensive electromagnetic simulations were conducted using CST Studio Suite 2025, followed by experimental testing under active jamming conditions. The results indicate that the QHA provides superior signal stability and preserves 3D Fix positioning continuity more effectively than the patch antenna under interference. Once the jammer is activated, the C/No of the patch antenna drops to approximately 0 dB-Hz, while the QHA maintains values near 35 dB-Hz. This result confirms its substantially higher resistance to jamming.

ABSTRACT. This work presents a low-cost 6 GHz reflectarray prototype intended for early-stage CubeSat antenna research, emphasizing accessible fabrication using standard FR-4 laminate and a manually assembled copper-sheet E-plane horn. The complete prototype costs approximately $60 while preserving the phase range and reflection response required for beam synthesis. Simulations predict a 33 dBi broadside gain for the 24-by-24-element surface under oblique feed illumination. Outdoor spectral measurements at 20~m confirm beam redirection, showing a clear co-polarized peak at broadside, near 10 dB cross-polar attenuation, and no observable response at an off-axis angle. Although limited in angular sampling, these results demonstrate the feasibility of low-budget reflectarray prototyping for CubeSat-oriented experimental studies and motivate further work toward full radiation-pattern characterization and deployable implementations.

ABSTRACT. This paper presents the design, fabrication, and evaluation of a compact, bio-inspired CPW antenna operating in the sub-GHz band, integrated with an Artificial Magnetic Conductor (AMC) and layers for WBAN applications, which stands out as a low-profile, low-cost solution. Miniaturization is achieved by combining a conductor based on Gielis'superformula and L-shaped inductors in the transmission line, resulting in resonance at 915 MHz. Experimental validation was performed using a multilayer phantom (comprising skin, fat, and muscle) with dielectric properties adjusted to match reference values. The simulation results indicated |S₁₁| = –21.33 dB at 922 MHz, while the measurements showed a shift to 946.6 MHz with |S₁₁| = –17.42 dB for the antenna in free space. The results confirm the antenna's potential for low-frequency biomedical applications, with high efficiency and adequate operation close to the human body.

ABSTRACT. We introduce a spectral representation for electromagnetic fields generated by electric dipoles in cylindrical biaxial anisotropic media. Our approach uses a medium parameter condition to decouple the field components, reducing the problem to solving a Sturm-Liouville equation for the axial electric field. The resulting Green's function is expressed in a spectral form, and we employ a modified integration path in the complex plane to ensure rapid convergence. Our findings are promising for practical applications in oil and gas exploration.

ABSTRACT. This work presents a new method for synthesizing annular apertures with circular symmetry, based on the Method of Stationary Phase. The synthesis is performed in two steps: first, a mapping between the aperture and radiation variables is done, and then, using this, the solution of a differential equation will generate the synthesized field. Two examples of synthesis are presented.

ABSTRACT. We understand the beauty of Antennas, Formulas, Equations in the publications of Harald Trap Friis, PhD, and many others. Today, we recommend sharing the classic papers: pass them along, cite, teach, and advance the field. Friis was director radio research at Bell Laboratories, then director of research in high frequency and electronics, in a position to have known, managed, and collaborated with many of the experts who shaped the field. Friis prepared an ‘Introduction to radio and radio antennas’ in 1971. As a Role Model in the field, Friis’s materials provide a guide. We add attention to numeracy skills, with spillover impact for accessibility, and amateur radio for hands-on experience for students of all ages.

ABSTRACT. A miniaturized wideband implantable antenna with wide axial ratio bandwidth is proposed for modern body centric wireless systems. The antenna is designed on Rogers 5880 substrate with overall size of 7 × 7 × 0.254 mm³, the design employs circular slot extensions and three shorting pins to achieve size reduction and multiple resonant paths. The antenna provides a wide impedance bandwidth from 1.2–5 GHz, including a strong 4.8-GHz resonance with –34 dB reflection coefficient and –12 dBi gain. Its symmetrical layout ensures stable radiation within multilayer tissues. With compact dimensions and wideband operation, the proposed antenna is well suited for biomedical implants and in-body telemetry applications.

ABSTRACT. This paper presents a new extension of a GPU-based discontinuous Galerkin time-domain (DGTD) solver that incorporates the Drude dispersion model to accurately simulate metallic and plasmonic materials at optical and terahertz frequencies. The proposed framework builds upon a previously developed GPU-DGTD solver with a third-order local time-stepping (LTS) scheme, enhancing its capability to handle frequency-dependent permittivities in a fully explicit and parallel manner. Numerical experiments on the scattering by a silver nanowire cylinder demonstrate the accuracy of the proposed formulation when compared with analytical Mie theory and its efficiency improvement due to the combined GPU-DGTD-LTS implementation. The developed tool provides an efficient and flexible platform for modeling photonic structures, metamaterials, and nanoplasmonic components.

ABSTRACT. This study presents a seven-year time series of water vapor attenuation at 142 and 240 GHz within a high-humidity tropical climate. The study combines GNSS delay data from the IGS station in the Bolivian Amazon, from ERA5 climate reanalysis and the latest ITU-R model. Zenith attenuation peak values of up to 7.11 dB (142 GHz) and 21.36 dB (240 GHz) are observed primarily during summer, with elevated levels also noted in spring and fall.

ABSTRACT. We introduce U-Net convolutional neural networks that estimate received-power maps around cellular base stations (BS) using only 0.045% of measured pixels in 256 × 256 maps. These maps can help regulatory bodies verify the compliance of EMF exposure guidelines. The models are trained with a log-distance path loss model and calibrated with real-life measurements. We obtain MAE and RMSE of approximately 4.5 dB and 5.8 dB, respectively, with respect to measurements when evaluating frequencies of 1.95 GHz, 2.13 GHz, and 2.65 GHz).

ABSTRACT. The wet antenna effect has been identified as the primary cause of the unexpectedly high attenuation values observed in 5 GHz microwave links. The Poisson model has been shown to effectively simulate this type of attenuation under varying weather conditions. However, there is currently no specific Poisson model that addresses this effect. This investigation aims to fill that gap by proposing a simplified version of previously developed Poisson models for estimating 5 GHz signal attenuation. The model validation results show strong predictive performance, with a pseudo R-squared value of 40.78% and a correlation coefficient of 66.44% between the observed excess attenuation values and the predicted attenuation influenced by the wet antenna effect.

ABSTRACT. Fixed Wireless Access at 28 GHz enables high-capacity indoor broadband but is highly sensitive to channel conditions. We conducted a comprehensive measurement campaign in corridors and offices using an omnidirectional receiver. Power-law models fit path gain with RMSE of 1.4 dB (LOS) and 6.4 dB (NLOS), outperforming reference models. Corridor waveguiding reduces path loss slopes, while entering offices adds 39 dB loss. Throughput analysis shows 7 Gbps (LOS) and 5.5 Gbps (NLOS) for 400 MHz, scaling proportionally with bandwidth. Results provide a robust basis for indoor FWA deployment and realistic system design.

ABSTRACT. This paper presents the results of path loss measurements of a link operating at the 60 GHz millimeter wave frequency in indoor auditorium environment in LoS and NLoS conditions within the campus of the National University of Colombia in the city of Bogota D.C. An experimental setup was used to measure path loss at millimeter wave frequencies, which integrates several hardware and software components to perform the measurements. The results of the experimental tests were compared with the 3GPP TR 38.901, METIS and NYU reference models and a fit using a lognormal distribution was performed to obtain a characterization of the path loss. These results are expected to be important to analyze the indoor coverage behavior of a 60 GHz millimeter wave frequency band network for aplications for 5G/6G or WiGig in Colombia.

ABSTRACT. We characterize a compact 2 X 2 dual-polarized self-grounded-bowtie array (1.6–3.0 GHz) and show how polarization non-orthogonality Ip and amplitude imbalance Ia govern MIMO efficiency in RLOS at 2.5 GHz. Using embedded-element far-fields and S-parameters, we map Ip and Ia to the measured efficiency for 2 X 2 spatial diversity (SD) based on maximum ratio combining (MRC) and spatial multiplexing (SM) based on zero-forcing (ZF). Bit-stream coverage at 2.5 GHz highlights the directional penalties from non-orthogonal polarizations.

ABSTRACT. This work presents a dual-port planar microwave sensor designed for non-destructive determination of the void index in lightweight mortars. The sensor operates based on variations in the dielectric permittivity of the mortars under test (MUT), which correlate with the vermiculite content in the mixture. The device was designed and simulated using Ansys HFSS, and measurements were performed with a vector network analyzer (VNA). The results demonstrate a downshift in the resonance frequency with increasing void index and the dielectric permittivity also increases, highlighting the potential of the proposed structure for quality assessment in construction materials.

ABSTRACT. This research paper presents the design, simulation, fabrication, and characterization of a compact antenna operating in the Industrial, Scientific, and Medical (ISM) band (4.65GHz – 6.075 GHz) and provides a high gain wideband (1.4250 GHz) for wearable devices. This antenna is designed for wearable medical devices. The designed antenna has shown good performance including its return loss (>-35dB), Bandwidth (1.425GHz), radiation pattern, gain 10dB, and efficiency.

ABSTRACT. This work presents a point-wise phase retrieval (PR) algorithm for estimating the phase of electromagnetic (EM) fields using interferometric techniques. The algorithm exploits punctual field interactions to reduce the PR problem in terms of geometric relations of the field vectors involved in the interfered field. Numerical and experimental tests were made to demonstrate the feasibility of the algorithm. The results show strong agreement between the retrieved and reference phases with errors below 9% in both cases.

ABSTRACT. This work addresses the challenge of detecting water contamination in gasoline, a recurrent form of fuel adulteration with economic, environmental, and operational impacts. We propose a compact two-port microwave sensor that integrates a Complementary Split Ring Resonator (CSRR) with an interdigital capacitor (IDC) to enhance sensitivity to dielectric changes in liquid samples. The combined CSRR–IDC topology strengthens the electromagnetic interaction with the test material, enabling more accurate identification of low-concentration contaminants. Microwave experiments were conducted to characterize the sensor’s response for different water levels in gasoline. The sensor exhibited a sensitivity of 1.45%, demonstrating its effectiveness for non-destructive detection of fuel adulteration.

ABSTRACT. A microwave-based label-free biosensor was designed and tested to detect anti-p53 antibodies, an early detection biomarker of cancer. The biosensor utilized a 50-Ω microstrip line with stepped impedance resonators (SIRs) optimized to resonate at 5.25 GHz. Experimental evaluations showed that the biosensor could detect binding events with a linear response from 10 up to 1250 pg/ml, a sensitivity of 0.104 MHz•ml/pg, and a limit of detection (LOD) of 315.7 pg/ml. The biosensor demonstrated effective biomolecule detection, paving the way toward affordable early cancer biomarker detection.

ABSTRACT. This paper presents a lightweight, flexible mmWave antenna-based wearable sensor capable of non-invasively monitoring skin hydration. The sensor, which is made on a 10x10x1 mm3 PDMS substrate, has dual-band (22.17-24.02 GHz), (26.33-40.56 GHz) and resonates at 32 GHz. A three-layer human tissue phantom that replicates three skin hydration levels—dehydrated, normal, and hydrated—with corresponding εᵣ and tanδ values was created to confirm sensing capability. Due to variations in the skin's effective permittivity upon hydration, the antenna shows different resonance-frequency shifts. When the hydration level changes from normal skin to dehydrated skin, the frequency shifts to the lower side. For dry skin, there was changes of 1.37 GHz, 410 MHz, whereas for hydrated skin, showed changes of 170 MHz, 180 MHz. This shows that the suggested mmWave design has a high sensitivity for detecting small variations in the local water content and skin state. This sensor has significant potential for wearable diagnostics in real time and smart healthcare.