This paper investigates the RF electrophoretic response of ellipsoidal gold nanoparticles (AuNPs). Since the existing works generally consider the electrophoretic heating of spherical AuNPs, this work provides an important step towards understanding the behavior of ellipsoidal AuNPs. We first develop an analytical framework for modeling of electrophoretic response of ellipsoidal AuNPs. Thereafter, due to the lack of experimental studies of non-spherical electrophoretic RF heating of AuNPs, we validate our theory by comparison to the existing experimental results of spherical AuNPs as a special case, and estimate a few additional parameters not considered before. Then, parameter studies are performed on surface charge, friction constant, frequency, and ionic background, with respect to AuNP size and shape. Finally, we present new results for the electromagnetic absorption and heat rates of ellipsoidal AuNPs in human tissue. Our results from the tissue testing indicate a strong difference between aqueous media and realistic human tissues due to the major difference in the host medium viscosity. We demonstrate the electrophoresis' strong dependency on the host medium's viscosity, where we note that cancer tissue viscosity is more than a thousand times higher than that of water. We thereby confirm negative results for RF AuNP heating, indicated by our own previous study and two other previous studies. Our results provide important insights into the feasibility of RF AuNP heating in a medical context.

This article presents the design of a high-gain, highly isolated four-element multiple-input multiple-output (MIMO) antenna system operating at the millimeter-wave (mm-wave) 28 GHz frequency band. The radiating element of the MIMO antenna comprises a 1 × 2 array of crescent-shaped patch elements backed by a full ground plane, having overall dimensions of 33 × 33 mm² (3.08λ × 3.08λ), where λ is the wavelength at 28 GHz. A 0.787-mm-thick low-loss dielectric substrate having a relative permittivity (ε<inf>r</inf>) of 2.2 and a loss tangent (tanδ) of 0.009 is used for the antenna design. It is observed that the designed radiating element provides resonance at 28.18 GHz and has a 6.21% fractional bandwidth (FBW) and a peak realized gain of 10.5 dBi. The radiation and total efficiency of the radiator are noted to be >85% and ≥75%, respectively, in the operating bandwidth. For polarization diversity and high isolation characteristics, the MIMO elements are arranged in an orthogonal manner, which helps achieve an isolation of >22.5 dB for adjacent elements and >32.5 dB for diagonally placed elements in the entire band of interest. Furthermore, MIMO system parameters such as envelope correlation coefficient (ECC) <0.003, diversity gain (DG) >10 dB, total active reflection coefficient (TARC) < −10 dB, and channel capacity loss (CCL) <0.5 bps/Hz are observed, which fall within the operational limits. Based on the achieved outcomes, the proposed design is well suited for mm-wave 28 GHz communication devices.

In this study, we introduce a cost-effective antenna designed for ultrawideband (UWB) spectrum. The antenna employs a single-layer coplanar waveguide (CPW) feed on a 1.6 mm FR4 board. Notably, the antenna demonstrates a bandwidth from 3.7 to 15.7 GHz (12 GHz) for a single element. Expanding its utility, a four-element Multiple Input Multiple Output (MIMO) assembly is arranged orthogonally, aiming to achieve diversity characteristics. The MIMO elements are connected through a common ground plane. In the MIMO configuration, the bandwidth response is increased to 2.9–16.2 GHz. To mitigate mutual coupling between the antenna elements, a simple geometric parasitic element is inserted between them, resulting in a significant improvement of 15 dB in isolation. In addition, a maximum gain of 5.5 dBi is noted at 14 GHz with total efficiency exceeding 80% throughout the resonance bandwidth. The individual antenna element boasts a compact footprint of 20 × 26 mm2, while the MIMO configuration occupies an area of 46 × 48 mm2. Furthermore, we conduct a thorough analysis of various MIMO performance metrics, including the envelope correlation coefficient (ECC), mean effective gain (MEG), and diversity gain (DG), all of which fall within acceptable thresholds. These analyses validate the potential of our proposed UWB–MIMO antenna for diverse UWB applications.

Metamaterials are mostly studied using the time-harmonic approach, where the wave propagation is spatially described. Recently, studies of media having electromagnetic properties that change in time have been given the attention of the scientific community, aiming to describe wave-matter interaction in both space and time. In the present paper, we use the space-harmonic method for the general description of wave propagation in time. Such a method can be used to effectively describe a "temporal multilayered" (or temporal multi-stepped) metamaterial by alternating the effective material parameters of the medium in time between two values. We obtain the exact analytical solution for the fields in two examples of temporally periodic metamaterials. Numerical simulations for the impedance-matched scenario are also carried out, showing an excellent agreement when compared to the exact analytical field. Our results also demonstrate the duality between the descriptions of the temporally periodic metamaterial and its spatial counterpart, spatially periodic metamaterials.

In this paper, we study transverse electric (TE) wave propagation inside a hollow circular waveguide filled with a lossy graded multilayered dielectric composite. The dielectric composite grading and the wave propagation are directed along the z-direction. The z-dependent permittivity of the dielectric composite is modeled using a periodic sinusoidal function. The exact analytical solutions to Maxwell's equations are obtained, and the field solutions and wave behavior confirm the expected properties of a lossy graded multilayered dielectric medium inside a hollow circular waveguide. Thereafter, through a numerical study performed using the commercial software COMSOL Multiphysics, we show that the analytical and numerical results are in perfect agreement. The analytical model applies to any combination of the material parameters relevant to the graded multilayered dielectric medium. The significance of the proposed method is that it can be utilized for analytically studying wave propagation and wave phenomena in a variety of media with characteristics including, but not limited to, periodicity, grading, negative refraction, and spatial- and frequency dependence. The validity is not restricted to any given frequency regime, therefore, allowing the proposed method to be useful for different types of applications, such as super-resolution imaging, electromagnetic cloaking, sub-wavelength focusing, and microwave absorbers.

This paper presents a novel wideband circularly polarized (CP) cavity-backed slot antenna based on Substrate Integrated Waveguide (SIW) technology, designed for compact and high-efficiency performance. The proposed antenna utilizes a hexagonal SIW cavity to simultaneously excite two closely spaced resonant modes (TM110 and TM210 ), resulting in enhanced bandwidth for linear polarization (LP). To achieve circular polarization, a passive, single-layer linear-to-circular polarization converter is integrated above the cavity, offering a structurally simple and PCB-compatible solution. Unlike conventional CP designs that rely on complex feeding networks or multilayered structures, this configuration maintains a planar profile and efficient performance. A fabricated prototype demonstrates strong agreement between simulation and measurement, achieving a peak gain of 9.2 dBic and a 14% axial ratio (AR) bandwidth. These results highlight the antenna's suitability for modern wireless systems requiring wideband CP functionality, including satellite communications, 5G modules, and compact embedded devices.

This study presents a novel, compact, diamond-shaped Multiple Input Multiple Output (MIMO) antenna system for 5G wireless communication. The proposed MIMO antenna system encompasses an array configuration, with each array unit comprising two antenna elements. The array elements are then orthogonally oriented making it a dual-port MIMO antenna system. The system is printed on a commercially available Rogers 5880, characterized by a permittivity ( epsilon(r) ) of 2.2 and a loss tangent (tan( delta) ) of 0.0009. The overall dimensions of the MIMO antenna system are 26 x 16 x 0.254 mm(3), operating in an mm-wave band with a frequency spectrum spanning from 26.2 to 34.2 GHz. The single antenna element exhibited a gain of 3.8 dBi and is then improved up to 7.6 dBi with two elements array arrangement. The system exhibited satisfactory MIMO characteristics with a maximum diversity gain of 10 dB, an envelope correlation coefficient of less than 0.0005, and an impressive 25 dB isolation between the antenna elements. Moreover, the proposed MIMO antenna array consistently maintained a radiation efficiency exceeding 90% across the entire desired frequency spectrum. Measurements were conducted with fabricated prototypes to validate the simulation results and were found in good agreement. The remarkable features of the proposed MIMO antenna system, such as compact size, wide bandwidth, good efficiency, and satisfactory gain values make it a promising candidate for 5G millimeter-wave wireless communication networks.

This paper investigates the RF electrophoretic response of ellipsoidal gold nanoparticles (AuNPs). Since the existing works generally consider the electrophoretic heating of spherical AuNPs, this work provides an important step towards understanding the behavior of ellipsoidal AuNPs. We first develop an analytical framework for modeling of electrophoretic response of ellipsoidal AuNPs. Thereafter, due to the lack of experimental studies of non-spherical electrophoretic RF heating of AuNPs, we validate our theory by comparison to the existing experimental results of spherical AuNPs as a special case, and estimate a few additional parameters not considered before. Then, parameter studies are performed on surface charge, friction constant, frequency, and ionic background, with respect to AuNP size and shape. Finally, we present new results for the electromagnetic absorption and heatrates of ellipsoidal AuNPs in human tissue. Our results from the tissue testing indicate a strong difference between aqueous media and realistic human tissues due to the major difference in the host medium viscosity. We demonstrate the electrophoresis’ strong dependency on the host medium’s viscosity, where we note that cancer tissue viscosity is more than a thousand times higher than that of water. We thereby confirm negative results for RF AuNP heating, indicated by our own previous study and two other previous studies. Our results provide important insights into the feasibility of RF AuNP heating in a medical context.

This paper presents a compact penta-band Multiple Input Multiple Output (MIMO) Dielectric Resonator Antenna (DRA). The proposed MIMO DRA consists of two rectangular DRs incorporating complementary split ring resonators (CSRRs) and an inverted T-shaped slot. The MIMO DRA achieves low impedance matching through simple microstrip feedlines, which is further enhanced by integrating a microstrip line with the DRA itself. Remarkably, the introduction of CSRRs enables the design to resonate at five distinct frequency bands, namely 2.8-GHz, 4.4-GHz, 5.8-GHz, 6.4-GHz, and 6.9-GHz. The simulated properties of the MIMO DRA were validated through over-the-air measurements performed on a fabricated prototype. The proposed MIMO design demonstrates impedance bandwidths of 2.09 %, 2.43 %, 2.17 %, 2.55 %, and 4.91 % at the above respective resonance frequencies. The proposed design exhibits exceptional stability in radiation pattern, featuring a noteworthy peak gain of 6.08 dBi and an efficiency of 91.35 %. Notably, the incorporation of an inverted T-shaped slot effectively enhances isolation between the MIMO elements, achieving a maximum diversity gain of 10 dB and an envelope correlation coefficient of 0.005 over 20-dB isolation. A good agreement between the simulation and measured results is obtained, which underscores the suitability of the CSRR-based MIMO DRA for multiband wireless applications (blue tooth, radio astronomy, remote sensing, WIFI, satellite television and 6G), making it a very valuable contribution to the field.

This paper introduces a novel method for estimating the path loss value in indoor scenarios. It uses a combination of electromagnetic calculation and machine learning. Using electromagnetic software, we design the indoor environment and calculate path loss between the receiver and the transmitter antennas, which are situated randomly with respect to the transmitters for better coverage. The transmitter antenna is modeled by employing the 3GPP standards. The indoor NLOS and LOS scenarios are measured over a 47-m separation distance between the RX and TX antenna locations. As it comes to fitting real measured data that has been acquired via measurement campaigns, the suggested models perform better overall. The achieved data is used to predict path loss using empirical models like FI and CI, and the mean absolute error percentages obtained are 5.87 and 6.61, respectively. After that, deep neural network and CatBoosting methods are employed to predict and estimate the PL precisely in the indoor environment. The mean absolute error percentages obtained are 4.4 and 3.3 for deep neural network and CatBoosting, respectively. Predicting PL, deep neural network, and CatBoosting methods outperform CI and FI by modelling complex, non-linear relationships, incorporating a broader range of features, adapting to diverse environments, and generalizing more effectively from data. These benefits are well-matched for modern wireless communication systems, where accurate estimation of signal loss is essential for maximizing network performance.