This article examines the benefits of utilizing site and orbital diversity reception techniques at Ka- and Q-bands in South Eastern Europe, comparing their performance in Cyprus and Greece. The assessment relies on measured rainfall rate statistics, collected near the selected locations in both countries. The study compares and evaluates the performance of double and triple site and orbital diversity scenarios. The simulation outcome reveals that the adoption of double and triple site, or double and triple orbital diversity configurations leads to considerable enhancements in outage performance in both frequency bands. The delivered improvements are markedly significant when specifically 3-site and 3-orbit diversities are applied, especially at Q-band. However, the orbital diversity demonstrates inferior performance compared with site diversity. Notably, for satellite systems demanding extremely high levels of service continuity, the 3-site diversity approach proves highly effective at Ka- and Q-bands, accomplishing this without necessitating overly large fade margins. Comparing Cyprus and Greece, the latter demonstrates lower outage improvements due to the higher measured rainfall rates. Finally, for a dual orbital diversity scenario in Greece, measured experimental results are presented in terms of joint attenuation and compared with the theoretical model, exhibiting noticeable accuracy.

A sparse high-gain multifaceted circularly polarized antenna array based on partially reflecting surfaces (PRSs) is designed. Circular polarization is obtained by implementing the sequential phase rotation method at the source antenna level. Beamforming is implemented using phase compensation combined with amplitude weighting proportional to the radiated intensity of the given facet in the targeted direction, following the maximum ratio transmission concept. The radiation pattern is scanned across the angular region specified by the angular gap between adjacent facets. The obtained beamformed result shows a maximum gain fluctuation smaller than 0.5 dB across the scanned sector, together with a sidelobe suppression of 10.27 dB, and the obtained embedded element pattern exhibits a flat top.

This study presents the development of a 3D-printed, wideband, dual-polarized magneto-electric dipole antenna. The proposed antenna demonstrates exceptional cross-polarization isolation (XPI) between its two mutually orthogonal RF ports, achieved through innovative feeding probes, specifically an inverted $\Gamma$-shape and a conventional $\Gamma$-shape probe. The analysis reveals that misalignment between probes can impair XPI; this phenomenon is systematically examined through electromagnetic full-wave simulations. A practical remedy is provided using four plastic rods strategically positioned through the probes and posts. Measurements indicate that XPI exceeds 50 dB across the common operating frequency range of 3.05–4.13 GHz (30%). The maximum realized gain is approximately 7.9 dBi, with a nearly flat response and stable radiation patterns across both ports throughout the bandwidth. The proposed antenna offers a cost-effective, 3D-printed design, wideband radiation performance, and exceptional port-to-port isolation, demonstrating significant potential for full-duplex wireless communication and ICAS applications.

This paper presents an actively controllable nonreciprocal metasurface based on a ferrite–patch structure with PIN diodes for dynamic control. Two activation methods are investigated: (a) phase control, which enables a 30° transmission-phase shift while maintaining nonreciprocal behavior, and (b) ON–OFF control, which switches the response by altering the propagation path. The phase-control metasurface is analyzed using transmission-line theory, full-wave simulation, and experiments, showing good agreement across methods. The ON–OFF design is optimized to suppress bidirectional transmission when ON. Experimental results confirm strong nonreciprocity, though slight frequency shifts arise from FR4 variability, and a back-fitted simulation improves consistency. The proposed dual-control framework provides a compact and low-cost approach to reconfigurable nonreciprocal surfaces that retain the use of permanent magnets for ferrite bias and are applicable to microwave wireless systems, including adaptive isolation, interference control, and tunable shielding. The results demonstrate the feasibility of compact, reconfigurable nonreciprocal metasurfaces using simple biasing circuits and offer design insights for frequency-stable implementations.

This paper proposes an electronically controlled reconfigurable scanned array that uses movable short phase shifters suitable for 6G applications. Excellent performance is demonstrated by the passive electronically scanned array (PESA) operating in the centimeter-wave frequency region (13–17 GHz). Four digitally controlled variable reflect-type phase shifters, each built with a $90^\circ$ hybrid coupler with a movable short circuit, are integrated with a $ 2 \times 2$ horn antenna array. The assembly also has E–H feeding networks, which help the antenna array receive a uniform signal distribution. Outstanding performance is demonstrated and verified by time and frequency domain simulation results of the full PESA, which show continuous main-lobe scanning in the azimuth and elevation planes. Over the operating bandwidth, the proposed PESA maintains a steady gain of $14 \pm 2$ dBi while achieving a matching level below $-$12 dB.

This paper presents a low-cost and highly integrated stacked patch antenna-in-package (AiP) solution for millimeter-wave communication. The design features two stacked patches with unequal dimensions to enhance bandwidth via dual close resonances, together with an antiphase feeding technique that suppresses cross-polarization without extra circuit complexity. In addition, a full codesign methodology is developed, incorporating antenna feeding, stripline-based matching networks, BGA parasitic modeling, and coaxial-like transitions discontinuities. The core building block is a 2 × 2 sub-array integrated with a flip-chip beamforming IC on a standard 10-layer organic high-density interconnect (HDI) substrate. The fabricated 2 × 2 AiP module achieves a measured fractional bandwidth >15% (25.9–30.3 GHz), a realized gain of 9.3 dBi, a total efficiency exceeding 90%, and a cross-polarization level better than −40 dB at 28 GHz. To validate scalability, four identical sub-arrays are tiled to form a 4 × 4 array, which demonstrates a measured peak gain of 15.1 dBi and maintains high radiation efficiency (>78%). This work validates the proposed HDI PCB-based approach as a viable, cost-effective, and scalable solution for medium-to-large scale 5G/6G phased arrays.

Simulation of precipitation for automotive radar validation requires suitable rain clutter models to test radars against various weather conditions. Although there have been developments in the investigation of attenuation due to rain, rain back-scattering needs to be explored further. However, the analytical modeling is challenging. Even if the raindrops are considered perfect conducting spheres, the Rayleigh approximation cannot be used to calculate RCS since rain droplets are comparable to automotive radar wavelengths. Therefore, reflectivity measurements at different rain rates were conducted in an indoor rain facility. Based on the measured data, reflectivity from rain back-scattering for automotive radars is modeled using an empirical approach. The results indicate that reflectivity can be modeled using an inverse-gamma or inverse-Weibull distribution parametrized by rain rate, and that the observed distribution varies with the spatial range considered, highlighting the impact of range-dependent effects on rain clutter modeling.

The efficient computation of an image-based ray trace for a receiver moving along a linear trajectory in an urban area is considered. Sampling channel information at the Nyquist rate or higher imposes a considerable computational burden, and the proposed algorithm instead utilizes the observation that such receivers will enter and exit well-defined lit regions, which define the precise extent within which reflected and diffracted rays can potentially propagate. A simple model for the associated ray is created within each lit region, obviating the need to perform an independent ray trace for each receiver location. The simple model is based on field information computed at $M$ locations within the region. Polynomial and cubic spline interpolation is used to efficiently model amplitude and phase data along the trajectory. The paper validates the approach and demonstrates its effectiveness in the context of a simulated street-canyon environment.

This paper proposes and experimentally validates four origami-inspired reconfigurable waveguide antenna designs, including the vertical folded waveguide antenna, the tilted waveguide antenna, the bellowed tilted waveguide antenna, and the fan-fold horn antenna. Aimed at overcoming the inherent limitations of rigid waveguide, those designs use mechanical deformation to control electromagnetic performance. By leveraging simple folding mechanisms, those proposed structures can turn antenna’s key parameters such as operating frequency, beam direction, beamwidth, gain and beam shape without relying on active components or complex beamforming circuitry. All prototypes were handcrafted as proof-of-concepts and successfully demonstrated their targeted functionality, showing the great potential in applications that require occasional reconfiguration rather than rapid, continuous adjustment. These results also reveal how origami techniques can unlock new design freedom for compact, reconfigurable antennas for future communication and sensing system.

Additive manufacturing is an enabling technology for a wide range of applications, particularly within the domain of electromagnetism, where components and antennas can benefit from its use. The objective of this study is to design antennas with different effective permittivities using only a small number of dielectric materials that are compatible with additive manufacturing. A formalism based on the construction of macrocrystalline cells employing Bravais lattices is utilized to accurately analyze the homogeneity and properties of the materials. This formalism is then used to synthesize a specific effective permittivity with polymers or ceramics. Following experimental validation of the method, it was applied to the design of dielectric resonator antennas, which were then validated using measurements in C-band. This paper presents an original construction of a multipermittivity material based on the formalism outlined above. This development offers interesting possibilities for antenna designers.

This paper presents a low-profile on-glass antenna solution for smart building applications that supports both WiFi and Narrowband Internet of Things (NB-IoT) connectivity and can be integrated with glass doors and windows. As a preliminary step, five architectural glass types were characterized in terms of dielectric properties, leading to the selection of 3 mm clear glass as the optimal antenna substrate. The initial antenna, a rectangular monopole with asymmetric coplanar ground, demonstrated wideband operation from 1.53 to 2.63 GHz, covering the 2.1 GHz NB-IoT and 2.4 GHz WiFi bands, 1.72–3.9 dBi gain, high radiation efficiency, and a bidirectional radiation pattern suitable for coverage on both sides of the glass. To enable applications requiring directional coverage and higher gain, the antenna was combined with a dual-band artificial magnetic conductor (AMC) surface, implemented on a separate 3 mm clear glass substrate. This integration enhanced the forward gain to 7.7–8.4 dBi while suppressing backward radiation, with simulation and measurement results showing good agreement. The proposed AMC-integrated on-glass antenna therefore combines wide bandwidth, high efficiency, and flexible bidirectional or unidirectional operation, making it a strong candidate for next-generation IoT-enabled architectural elements in smart buildings.

This paper investigates the use of large Reconfigurable Intelligent Surfaces (RISs), also known as “Smart Skins,” to improve outdoor-to-indoor millimeter-wave (mmWave) propagation, taking advantage of ventilation holes commonly found – or easily implemented – in European buildings. By using a transmissive, focusing RIS, the signal can be concentrated and routed through the opening, enhancing signal penetration into the indoor space even in modern, highly insulated buildings that particularly hinder signal penetration. Using Ray Tracing simulations, we compare scenarios with and without RIS at 29 GHz, demonstrating significant indoor signal coverage improvements in the first case. The study highlights the use of RIS – or Smart-Skins – as a cost-effective solution to address the challenges of mmWave propagation in modern building designs.

This paper presents the design and evaluation of reflectarray antennas at spherical surfaces aimed at achieving an optimal compromise between electrical performance and mechanical deployability for satellite antenna solutions based on offset reflector configurations. By implementing printed reflectarray elements on a spherical surface, the phase-shifting elements mitigate spherical aberration, leading to enhanced focusing capabilities comparable to those of parabolic reflectors. The spherical geometry inherently simplifies the folding mechanism due to the rotational symmetry of the reflecting surface and minimizes the differential spatial phase delay, improving the reflectarray in-band performance. Simulation results demonstrate that large-aperture spherical reflectarrays can replicate the gain and beam quality of parabolic reflectors with smoother phase distributions than flat or multifaceted reflectarrays. The integration of spherical reflectarrays in dual-antenna configurations is evaluated to realize compact and efficient antenna systems for next-generation satellites.

This work proposes a band-switchable electrically small antenna (ESA) system for a wearable health monitoring device. The system operates at multiple 5G-NR bands (875–934 MHz and 1.72–2.2 GHz) using a switchable configuration. The antenna consists of multi-resonant shorted strips that have been miniaturized to fit in meandered form into an area of 63.2$\times$25 mm$^2$ (0.19$\times$0.08$\lambda^2$) available in the intended health monitoring device. To enable operation at two distinct modes, the antenna feedline has been integrated with a switch, which is then matched using lumped matching components. Results indicate that the ESA system operates at 875–900 MHz in Configuration 1, and at 898–934 MHz and at 1.72–2.2 GHz in Configuration 2. The device has been fabricated and integrated into a compact 3D printed casing prior to experimental evaluations. In addition to studying the switchable reflection and radiation performance, the ESA is also evaluated in the presence of a human body phantom. Simulated specific absorption rate levels are less than 0.47 W/kg averaged over 1 g of tissue, which complies with international standards.

Medical microwave imaging (MMWI) is emerging as a promising noninvasive diagnostic modality, offering a safe, portable, and cost-effective alternative to conventional imaging methods. Despite its potential, MMWI poses significant challenges due to the ill-posed and nonlinear nature of the underlying inverse scattering problem. Two main strategies are typically adopted: qualitative imaging, which yields rapid but approximate reconstructions, and quantitative imaging, which aims to recover the full permittivity distribution of tissues. Both approaches substantially benefit from accurate patient-specific background models that enhance reliability and reduce computational complexity. Building upon preliminary results presented at EuCAP 2025, this work advances the development of patient-specific head models for quantitative brain imaging. The study employs anatomically conformal basis functions and extends the model to include cerebrospinal fluid, which represents a strong scatterer with markedly distinct dielectric properties. The proposed framework improves reconstruction accuracy and convergence efficiency, thereby contributing to the advancement of quantitative MMWI toward practical clinical applications.

The rapid advancement of the miniaturization techniques for high-frequency transceivers, radars, and communication systems operating in the D-band (110–170 GHz) has positioned circular dielectric waveguides (CDWGs) as a promising transmission-line alternative. Yet, their potential has not been fully exploited. This work fills this gap by introducing novel, compact CDWG-fed lens antenna solutions that deliver excellent gain and impedance matching performance. A low-loss, low-cost, and flexible CDWG made of low-density polyethylene is used to excite dielectric lens antennas of various sizes, contours, and materials, enabling a systematic evaluation of the impact of lens geometry on antenna performance. Through detailed electromagnetic simulations and experimental validations, lenses of different sizes and contours are designed. The proposed CDWG-lens configuration achieves measured broadband matching better than 17 dB and stable high gain across 115–130 GHz. Measured gains of 21–23 dBi for lenses with diameter of 10.6 mm and gain factor of 27–28 dBi for lenses with diameter of 20 mm confirm the high aperture efficiency and novelty of this approach. A strong agreement between the simulation and the measurement results is also observed. These compact and efficient lens antennas combined with the advantages of CDWG feed, can be integrated as a part of advanced system applications in the D-band frequency range like radar sensing and communications.

This paper presents a differential split-ring resonator sensor, designed for the analysis of small volumes around 20 µl of liquid. One resonator is filled with a reference liquid while the other contains the liquid under test. Although the differential configuration reduces the influence of environmental parameters, it can lead to resonance overlap when the dielectric properties of the two liquids are close to each other. To overcome this limitation, a post-processing method based on Lorentzian fitting is used to accurately extract resonance parameters such as frequency and width, even when the resonances strongly overlap. The method is validated through experiments with water–ethanol mixtures of different concentrations. This shows excellent agreement between measured and calculated values. Eigenmode simulations are also performed to analyze field distributions, providing additional insight into resonance behavior. The proposed approach offers a reliable and general methodology for the analysis of differential resonant sensors.

Uncrewed aerial vehicles (UAVs) serving as aerial base stations (ABSs) are expected to extend 6G millimeter-Wave (mmWave) coverage and improve link reliability in urban areas. However, UAV-based air-to-ground channels are highly dependent on height and urban geometry. This paper proposes an ABS height-dependent mmWave channel model and investigates whether urban geometry, beyond the standard built-up parameters, significantly affects line-of-sight (LoS) probability ($P_{\text{LoS}}$) and large-scale fading (LSF). Using MATLAB ray tracing (RT) at 26 GHz, we simulate approximately 10K city realizations for four urban layouts that share identical built-up parameters but differ in their spatial organization. We extract elevation-based $P_{\text{LoS}}$ using a sigmoid model and derive height-dependent path-loss exponents (PLEs) and shadow-fading trends using exponential fits. Results show that PLE for non-LoS decreases toward $2.5$–$3$ at high altitudes, LoS PLE remains near $2$, and shadow fading reduces with height. We also find that geometric layout introduces a modest but consistent change in PLE ($\approx \pm 0.2$), even when built-up parameters are fixed. The proposed model matches RT results and provides a practical, height-dependent LSF model for ABS planning in urban scenarios.

Microwave hyperthermia (HT) is a promising adjunct therapy for breast tumors. This study investigates gold nanoparticle (GNP)-enhanced HT through three-dimensional electromagnetic (EM) simulation of a realistic breast phantom containing an embedded 5 mm tumor, excited by an eight-element fractal octagonal ring antenna (FORA) array operating at 2.45 GHz. A 5.85 nM concentration of 21 nm peptide-capped GNPs confined to the tumor region produces a 65–75$\%$ increase in peak specific absorption rate (SAR) and improves the target-to-breast quotient by 39–47$\%$ across both optimization methods, without introducing additional hotspots in healthy tissue. Two complementary optimization strategies are compared: Python-based genetic algorithm (GA) post-processing and direct optimization within CST. The Python/GA approach achieves a six- to seven-fold reduction in computational time (22–24 vs. 145–158 minutes), enabling rapid treatment planning for varying tumor geometries and nanoparticle concentrations. Baseline thermal modeling confirms that tumor temperatures reach 43–45$^\circ$C, within the therapeutic window for HT. These results demonstrate that GNPs effectively enhance EM energy focusing within the tumor region. The FORA antenna delivers the microwave energy, while the GNPs modify the target’s dielectric profile to selectively boost energy absorption-confining the heat to the tumor while safeguarding adjacent healthy tissue.’ Overall, this work provides computational evidence supporting the feasibility of GNP-enhanced microwave HT, while highlighting key optimization trade-offs between computational efficiency and protection of healthy tissue.