Radioelectronics and Communications Systems

On sum of Beaulieu-Xie shadowed variates and its application to maximum ratio combining diversity

2024-12-02T16:17:32+02:00

Sixth-generation (6G) communication systems use terahertz frequency bands. These enable high-speed data rates, enhanced reliability, and low latency. The Beaulieu-Xie shadowed (BXS) fading model effectively characterizes 6G wireless channels. This study computes the sum of Beaulieu-Xie shadowed variates for independent, not necessarily identically distributed (INID) random variables. Several statistical measures are derived using the moment generating function (MGF) for independent identically distributed (IID) maximum ratio combining (MRC) diversity. Performance is evaluated in terms of the n-th moment, outage probability (OP), and error rates. The proposed analytical expressions are validated by comparison with Monte Carlo simulation results and established small-scale fading models. These include Beaulieu-Xie, Nakagami-m, and Rayleigh as special cases.

Analysis of antenna elevation pattern impact on sporadic-E propagation computations under ITU-R P.2001

2026-09-13T23:42:01+03:00

A variant for improving the accuracy of automated prediction of radio wave propagation is considered based on the framework of Recommendation ITU-R P.2001-6. It is noted that, in many cases, one can improve computational accuracy by accounting for the antenna’s elevation radiation pattern. We pay particular attention to the model of radio wave propagation via sporadic-E reflection. Besides, we analyze the impact of terminal separation and the effect of antenna type on computation accuracy. We have also identified the corrections necessary for typical antennas operating in the short- and ultrashort-wave ranges, along with the limits within which these corrections apply. We identified areas for future research that would further improve the accuracy of predictions of radio wave propagation using Recommendation ITU-R P.2001. This technique accounts for four mechanisms of radio wave propagation. While implementing the automated method based on Recommendation ITU-R P.2001 in a practical computer information system, it was necessary to account for additional factors that were not explicitly considered in the original ITU Recommendation. However, these factors can significantly degrade the accuracy of radio wave propagation predictions.

Whispering gallery mode radiation on periodic local irregularities of dielectric resonator for mm-Wave sectoral antennas development

2025-04-09T10:58:25+03:00

A new effect of diffractive radiation of whispering gallery modes on local inhomogeneities in disk dielectric resonators is presented. The basis of a multi-beam radiation of electromagnetic energy in the full sector of azimuthal angles 0–360° is substantiated. It is found that local irregularities, equidistantly spaced on the operating surface of a disk dielectric resonator, generate intense electromagnetic radiation over the azimuthal sector 0–360°. The physical principles of operation, design features, and calculation of a segmented dielectric resonator with an operating surface in the form of a diffraction grating are shown. Moreover, the resonator’s far-zone radiating properties are presented. It is demonstrated that the radiated electromagnetic energy from the segmented dielectric resonator forms a multi-lobe radiation pattern across the azimuthal sector from 0 to 360°. The key feature is high gain values, which can reach up to 12 dB at various lobes and the operating resonant frequency.

Nature of thermal stability and losses in microwave dielectrics with high dielectric permittivity

2026-09-13T23:57:09+03:00

Microwave electronics requires dielectrics with a high dielectric permittivity and low losses. Promising composites are based on “hard” paraelectrics such as rutile or perovskite, which are characterized by a weakly damped soft transverse optical mode of crystal lattice vibrations and do not contribute to the formation of polar phases. The natural temperature instability of the dielectric permittivity of paraelectrics can be suppressed by introducing paramagnetic lanthanide ions. Relatively low losses in the microwave range can only be achieved in single-phase compositions and in the absence of polar inclusions in the structure. The paper attempts to explain the physical nature of the temperature stability of the dielectric permittivity and losses introduced by the polar phase.

Effect of temperature on noise graded InGaN diode characteristics

2026-09-14T00:03:34+03:00

Solid-state noise signal sources are utilized in various systems for both civilian and military applications. One mechanism that leads to noise fluctuations is interband impact ionization (II). The use of diodes in which impact ionization occurs in strong static fields formed near the cathode contact (cathode domain) is proposed to create noise generators in the frequency range from one to hundreds of GHz. InGaN-based diodes containing a graded gap layer and a low-doping region for the initiation of II and its localization on the cathode are considered. Diodes with a length of 1–4 μm are considered. Their simulation is carried out using a two-dimensional model of the diode and the ensemble Monte Carlo method. The different environmental temperatures and self-heating effects associated with impact ionization and current in diodes are considered. The direct-current and noise characteristics of the diodes were obtained over the external temperature range of 300 to 500 K. The temperature effect on physical processes in the diode and the frequency properties of the generated noise are shown.