Prof. M Khalaj-Amirhosseini,
Volume 11, Issue 4 (12-2015)
Abstract
The ideal analysis of planar diodes in Temperature Limited Region is presented. Two types of relations are obtained for electric potential and electric field distributions one accurate but implicit and the other almost accurate but explicit.
A. Y. Abdulrahman, O. S. Zakariyya, A. S. Afolabi, A.t. Ajiboye,
Volume 19, Issue 3 (9-2023)
Abstract
Abstract: Rain attenuation prediction models are inevitably deployed to provide rough estimates of the actual measured attenuation due to severe scarcity in most of the tropical and equatorial climates. The results of rain attenuation measurements over a 14.8 GHz terrestrial microwave link and slant-path attenuation in vertically polarized signals propagating at 10.982 GHz in a tropical Malaysian climate were reported in this study. The experimental results including the path adjustment factors were compared with the predictions of some selected rain attenuation models. The relative errors in the path length adjustment factors (PLAFs) are in the range -0.3370 – 2.6272, while those of the slant path adjustment factors (SPAFs) are -0.9252 – +0.2923. Moreso, the charts of PLAFs and SPAFs at 0.01% of the time were also presented because they are the most commonly used availability by the telecommunications service providers. This study will allow the radio engineer to select the most suitable prediction models for the particular region under study, thereby ensuring adequate radio planning for improved service delivery especially in the tropical climates due to their peculiarity.
Godday Biowei, Sulaiman Adeniyi Adekola, Kamoli Amusa,
Volume 20, Issue 2 (6-2024)
Abstract
This paper investigates the dynamics of mmWave at the free space-human skin interface. The four Fresnel equations tailored for parallel and perpendicular polarizations, are employed in the analysis. The research reveals that for human tissue with relative permittivities (18.99, 15.51, 13.35, 11.69, 10.40) and conductivities (22.48, 27.09, 29.76, 31.79, 33.38) S/m, when exposed to 5G mmWave frequencies (24, 30, 35, 40, 45) GHz, respectively, exhibits Brewster angles of (79º, 78º, 77º, 76º, 75º), respectively. Additionally, it is shown that Brewster angles exist between 60º and 80º which aligns with existing literature using Gabriel’s skin model. To further validate obtained results, use is made of the results of the Gabriel’s skin model at (40, 60, 80, 100) GHz with the respective permittivities and conductivities, to generate new power reflection coefficients for the parallel and perpendicular polarizations for the sake of comparative analysis. First, comparisons of the curves for the Gabriel’s skin model reported in the literature with this work, show fairly good agreements. Second, the Brewster angles of (78º, 76º, 74º, 73º) obtained from this work, for the respective frequencies compare favorably with (75º, 74º, 70º, 69º) extracted from Gabriel’s skin model curves reported in the literature, with all values falling within the expected range of 60º to 80º.
Ayoub Hamidi, Ahmad Cheldavi, Asghar Habibnejad Korayem,
Volume 20, Issue 3 (9-2024)
Abstract
This paper proposes a structure for concrete composite materials that effectively attenuates transmitted power through the composite slab across a wide frequency range. The proposed structure is practical for electromagnetic interference shielding applications. To assess its effectiveness, the proposed structure has been compared with two other structures: a traditional wire mesh used in reinforced composites and an array of helices, a cutting-edge technique for manufacturing lightweight concretes with significant improvements in shielding properties. The comparison among full-wave simulation results indicates that the proposed method leverages the benefits of both techniques. It achieves a shielding effectiveness exceeding 30 dB from low frequencies up to 8.5 GHz and beyond 55 dB from low frequencies up to 4 GHz. Furthermore, an experimental measurement was conducted to validate the full-wave simulation results. An experimental sample was fabricated according to the simulated proposed structure, and the measured shielding effectiveness confirmed the composite's capability in wideband electromagnetic shielding. Theoretically, the proposed structure can enhance the concrete's mechanical characteristics while improving its shielding effectiveness, making it suitable for designing ultra-high-performance concretes.
Seyed Hosein Mousavi, Aslan Nouri Moqadam,
Volume 21, Issue 1 (3-2025)
Abstract
Electromagnetic waves, with their unique properties, offer promising solutions to environmental challenges. This paper explores the utilization of electromagnetic scattering by droplets for cloud fertilization purposes. Specifically, a linearly polarized plane wave is deployed to stimulate a heterogeneous cloud medium composed of spherical droplets with varying size parameters. Through the application of Generalized Mie Theory (GMT) and Discrete Dipole Approximation (DDA) at a frequency of 28 GHz, multiple scattering phenomena and local electric fields are meticulously computed. Various scenarios of scattering, encompassing droplet diameters ranging from 500 µm to 700 µm and diverse volume fractions, are meticulously examined. Employing DDA and dyadic calculations, the exerted forces on individual spherical droplets are rigorously evaluated, with precise determination of force direction and components. The simulations robustly affirm the viability of droplet manipulation via plane wave excitation, thereby enhancing the likelihood of droplet collision and consequent cloud fertilization, ultimately leading to precipitation. Furthermore, the parameters of the incident wave can be deliberately adjusted to steer droplets towards denser regions, thereby augmenting the likelihood of successful fertilization events.
