Diffraction Losses Research Articles

Automatic Placement Algorithm of Base Stations Trunking Communication Systems

to increase the efficiency of the trunking communication systems design process, an original algorithm for the automatic placement of base stations is proposed, taking into account the real conditions of radio wave propagation. The analysis showed that the existing methods allow you to place base stations manually, with a given step or automatically, but without taking into account the propagation of radio waves, which leads to poor-quality coverage of the required area with communication. The aim of the work is to reduce the complexity of designing a trunking communication system that is guaranteed to cover a given service area. It is proposed to calculate the service areas of base stations using a statistical model, as well as taking into account additional diffraction losses on the radio signal propagation path. The solution to the problem of automatic placement of base stations is based on the use of the proposed modified Hut model, which takes into account the terrain at the locations of the base and portable stations, as well as on the international recommendation for predicting signal propagation on a specific route for ground services. With automatic placement, the optimality criterion is fulfilled, which consists in placing the minimum number of base stations necessary to cover the required territory. An element of the novelty of the presented solution is that at the first stage of the calculation, the service area of the base station is determined by the statistical method, at the second stage, an updated calculation of the service area takes place taking into account the actual conditions of radio wave propagation at the binding site, and at the third stage, the zone of guaranteed customer service is determined. The use of the proposed algorithm makes it possible to reduce the complexity of the system design process and determine the sufficient number of base stations needed to cover a given area with communication. Appropriate software has been developed to apply the algorithm in real practice. To confirm the effectiveness of the algorithm, the paper presents comparative calculations of the time spent on designing a trunking communication system using the developed software and using the widely used RadioMobile program.

Average Intensity of a Laguerre—Gaussian Vector Vortex Beam through Inhomogeneous Atmospheric Turbulence

We investigate the evolution properties of a partially coherent Laguerre–Gaussian vector vortex (LGVV) beam through inhomogeneous atmospheric turbulence. Analytical formulae for the elements of a cross-spectral density matrix of a partially coherent LGVV beam propagating in turbulence are derived with the help of the extended Huygens–Fresnel principle. Our outcomes demonstrate that the normalized initial profile of a partially coherent beam with concentric dark rings gradually evolves into a Gaussian-like beam profile in turbulence. We also find that the beam is emitted at a large zenith angle and quickly converts to a Gaussian-like beam. Furthermore, it is also shown that a propagation beam with a large topological charge has a stronger ability to resist atmospheric turbulence. In order to confirm our numerical results, we combine the complex screen method and multi-phase screen method to simulate the propagation of a partially coherent LGVV beam in atmospheric turbulence. It is indicated that the simulation results are in good agreement with theoretical predictions. Our results will pave the way for the development of free-space optical communications and remote sensing.

Properties of focused Laguerre–Gaussian beam propagating in anisotropic ocean turbulence

We analyze the properties of a focused Laguerre–Gaussian (LG) beam propagating through anisotropic ocean turbulence based on the Huygens–Fresnel principle. Under the Rytov approximation theory, we derive the analytical formula of the channel capacity of the focused LG beam in the anisotropic ocean turbulence, and analyze the relationship between the capacity and the light source parameters as well as the turbulent ocean parameters. It is found that the focusing mirror can greatly enhance the channel capacity of the system at the geometric focal plane in oceanic turbulence. The results also demonstrate that the communication link can obtain high channel capacity by adopting longer beam wavelength, greater initial beam waist radius, and larger number of transmission channels. Further, the capacity of the system increases with the decrease of the mean squared temperature dissipation rate, temperature-salinity contribution ratio and turbulence outer scale factor, and with the increase of the kinetic energy dissipation rate per unit mass of fluid, turbulence inner scale factor and anisotropy factor. Compared to a Hankel–Bessel beam with diffraction-free characteristics and unfocused LG beam, the focused LG beam shows superior anti-turbulence interference properties, which provide a theoretical reference for research and development of underwater optical communication links using focused LG beams.

The Data Transmission Process Optimizing Algorithm in the Designed Telecommunication Network Structure

The data transmission process optimization problem in telecommunication network is considered by experimentally calculating resources spent on transmitting data from one point of the designed network to another. The network structure is designed based on the algorithm for placing network nodes, taking into account diffraction losses inside the urban area. The calculation of the resources spent on data transmission is carried out by bypassing the entire network structure using the modified Kosaraju algorithm. This process is carried out iteratively using simulation until it satisfies the given conditions. An algorithm is being developed that uses signal loss calculation models, as well as a network structure bypass algorithm to analyze the data transmission process, which allows designing a network model.

An analysis of the efficiency and accuracy of applying Huygen's principle to acoustic scattering models

Over the last decade, the Target-in-the-Environment-Response (TIER) model has proven to be an efficient simulation tool for computing the acoustic scattering from axisymmetric objects in an underwater environment. The model functions by first computing the free-field scattered pressure via a high-fidelity Finite Element (FE) computation. The scattered pressure is converted into a scattering amplitude and stored in a look-up table. These scattering amplitudes are used in a fast ray model to compute the acoustic scattering from an object on or embedded in a seafloor, for any vehicle path imaginable. Computing the scattered pressure amplitude for the look-up tables via the FE method is a bottleneck of the computation. For monostatic scattering problems, the look-up table historically sampled the azimuthal angle domain with 1-deg resolution. However, this approach is not efficient in time nor disk space when moving to bistatic scattering situations. Here, we present a more efficient alternative, which is based on application of Huygen’s principle. The results from this method are assessed against the original sampling method and validated against additional high-fidelity models including a hybrid 2-D/3-D FE-Propagation model and a fully 3-D Impedance Matrix method, the latter of which is numerically exact and offers a benchmark solution.

Determining the Orientation of a Single-Crystal and the Absolute Energy of X-Rays Using Diffraction Losses

Determining the Orientation of a Single-Crystal and the Absolute Energy of X-Rays Using Diffraction Losses

The Method for Determining the Exact Single Crystal Orientation with Simultaneous X-Ray Energy Correction Using the Spectrum of Diffraction Losses

The Method for Determining the Exact Single Crystal Orientation with Simultaneous X-Ray Energy Correction Using the Spectrum of Diffraction Losses

Young’s double slit interference with vortex source

The fast and convenient demultiplex of optical vortex (OV) mode is crucial for its further application. We propose a novel approach that combines classic Young’s doublet with an OV source to effectively identify the OV mode through the analysis of interference patterns. The interference patterns of the OV source incident on the double slits can be perfectly illustrated by using both the classical double-slit interference method and the Huygens–Fresnel principle. The interference fringes will twist along the negative or positive direction of x axis when topological charge (TC) l > 0 or l < 0, and the degree of the movement varies with the TC, allowing for a quantitative display of the OV characteristics through the interference patterns. Additionally, we deduce analytically that the zeroth-order interference fringe has a linear relationship with the TC and the vertical position. These findings highlight the ability to identify the OV mode by analyzing the interference patterns produced by Young’s doublet.

Effect of oceanic turbulence on the propagation behavior of a radially polarized Laguerre-Gaussian Schell-model vortex beam.

Optical wireless communications applications are restricted by oceanic media-induced beam quality degradation. However, modulating the coherence and polarization structures of the laser beams can effectively diminish the negative influence of oceanic turbulence on the beams. The average intensity of a radially polarized Laguerre-Gaussian Schell-model vortex (RPLGSMV) beam propagating through oceanic turbulence is explored by employing the extended Huygens-Fresnel principle. We found that the average intensity of an RPLGSMV beam is greatly affected by oceanic turbulence with a large rate of dissipation of the mean-square temperature and a large relative strength of the temperature and salinity fluctuations as well as the small rate of dissipation of the turbulent kinetic energy per unit mass of fluid and small Kolmogorov microscale. It was also found that a RPLGSMV beam with a larger radial index, topological charge, initial coherent length, and beam waist has a stronger anti-turbulence ability. Our numerical findings may be of great significance for the detection and imaging of oceanic optical telecommunications links.

Discrete form of the Huygens-Fresnel principle: to the multi-dimensional analog of the Nyquist–Shannon sampling theorem

Discrete form of the Huygens-Fresnel principle: to the multi-dimensional analog of the Nyquist–Shannon sampling theorem

Second-order coherence and polarization characteristics of partially coherent radially polarized cosh-Gaussian vortex beams in a turbulent atmosphere

The second-order coherence and polarization characteristics of partially coherent radially polarized cosh-Gaussian vortex (PCRPChGV) beams in atmospheric turbulence are investigated based on the extended Huygens–Fresnel principle. The analytical propagation formulas of cross-spectral density matrix, average intensity and degree of polarization (DOP) for PCRPChGV beams in turbulence are derived. The influences of initial correlation length, cosh factor and turbulence intensity on average intensity, on-axis intensity and DOP of PCRPChGV beams are examined numerically. Results show that with increasing propagation distance, the PCRPChGV beam evolves from the initially separated double-lobe spot into overlapping double-lobe spot, and Gaussian spot. The corresponding intensities of the two Cartesian components of light field rotate markedly around the beam axis in a unique manner. Initial correlation length and cosh factor have an obvious influence on the position and size of normalized on-axis intensity peak, respectively. In addition, PCRPChGV beams in moderate turbulence have strong anti-turbulence ability.

Photoelectrochemical Water Splitting at Elevated Pressure: A Model-Based Evaluation

Photoelectrochemical (PEC) water splitting is one of the few truly renewable pathways towards “green” H2. Although PEC water splitting demonstration devices have been mainly operated at atmospheric pressure, most applications and processes that use H2 require it to be supplied at elevated pressure. Although PEC-generated H2 can be pressurized afterwards with e.g. mechanical compression, operating the PEC water-splitting device itself at elevated pressure offers an intriguing alternative and several possible advantages. For example, bubble formation is strongly reduced at elevated pressure, which lowers bubble-induced electrode deactivation and bubble-induced product crossover rate.[1,2] In addition, the optical reflection and diffraction losses induced by bubbles can be minimized.[3] Finally, the electrochemical production of hydrogen at higher pressure requires only a small (though not insignificant) increase of the thermodynamic cell voltage (29 mV for 10-fold increase in pressure).[4] The main disadvantage of a higher pressure is the increasing mechanical demands on the cell design, and the challenge is to find a pressure range at which optimum conditions will be achieved.To evaluate these pressure-induced effects, we have developed a two-dimensional multiphysics model that considers semi-empirical pressure-dependent bubble characteristics (e.g., bubble formation efficiency, bubble diameter) and their impacts on the multi-phase flow, electrochemistry, and mass transport in a membrane-free PEC water-splitting device. Based on the simulation results, a quantitative comparison between two technical approaches to generate pressurized H2 from a PEC device, namely operating PEC water-splitting at atmospheric vs. elevated pressure, has been conducted, as shown in the schematic diagram in Fig. 1a. Various performance loss factors in a PEC water-splitting device were considered, including bubble-induced product crossover, optical loss, and pH gradient-induced concentration overpotential. These losses (translated to kWh unit) were then compared with the specific work required to mechanically compress H2 from the collection pressure (p 1 in Fig. 1a) to 700 bar (p 2 in Fig. 1a). Our results show that bubble-induced optical loss is the predominant factor among all the losses considered. The overall loss diminishes as pressure increases, as shown in Fig. 1b. By comparing the benefit of conducting PEC water-splitting at elevated pressure (defined as the amount of losses avoided vs. operation at 1 bar) with the thermodynamic cell voltage penalty (see Fig. 1c), we found that no significant benefit can be gained by operating beyond 6 – 8 bar. Therefore, this pressure range represents a desirable range for the operation of a membrane-free PEC water-splitting device. Keywords : (photo)electrochemistry, water splitting, elevated pressure, multiphysics modeling, quantitative evaluation.

Quantitative Analysis of the Effect of Atmospheric Turbulence on a Bessel–Gaussian Beam

Suppressing the impact of atmospheric turbulence on laser beam propagation is a bottleneck problem in the application of free space optical communications, with the primary difficulty being the lack of a quantitative description of the effect of turbulence on a laser beam. In this paper, we propose a quantitative description of the effect of turbulence and express a quantitative analysis of the effect of atmospheric turbulence on Bessel–Gaussian beam based on the extended Huygens–Fresnel principle. The results of numerical analysis confirm the validity of the theoretical description. This study also shows that the influence of turbulence is stronger when the annular shape of the Bessel–Gaussian beam is more obvious. The method also provides theoretical guidance for reverse engineering the amplitude and phase distribution of the initial laser beam, thereby effectively reducing the impact of atmospheric turbulence on laser beam propagation.

Determination of Diffraction Losses and Coverage Inaccuracies in Some Mountainous Regions of Southern Nigeria

Determination of Diffraction Losses and Coverage Inaccuracies in Some Mountainous Regions of Southern Nigeria

Analytical Model of Three-Dimensional Ultrasonic Beam Interaction with an Immersed Plate

This paper proposes an analytical model to describe the interaction of a bounded ultrasonic beam with an immersed plate. This model, based on the Gaussian beams decomposition, takes into account multiple reflections into the plate. It allows predicting three-dimensional spatial distributions of both transmitted and reflected fields. Thereby, it makes it easy to calculate the average pressure over the receiver’s area taking into account diffraction losses. So the acoustical parameters of the plate can be determined more accurately. A Green’s function for the interaction of an ultrasonic beam with the plate is derived. The obtained results are compared to those given by the angular spectrum approach. A good agreement is seen showing the validity of the proposed model.

Average intensity of Bessel-Gauss beams propagating through Kolmogorov turbulence with the quadratic structure function.

It is well known that in free space propagations, Bessel-Gauss (BG) beams are non-diffractive, in the sense that over a finite distance the beam mainlobe does not spread. Non-diffraction beams have been found to offer advantages over diffractive beams, for example, in terms of power delivery. However, in random media, such as a turbulent atmosphere, the performance of BG beams is still an active area of research. For example, applying the extended Huygens-Fresnel (EHF) principle results in an intractable expression for the optical field and the average intensity. This work is concerned with finding a closed-form expression for the average intensity of BG beam propagating through weak and strong Kolmogorov turbulence under the quadratic structure function (QSF) assumption. This is achieved by considering the average intensity convolution integral of the free space intensity with the point spread function (PSF). This convolution integral is reduced to a one-dimensional integral that can be easily evaluated in closed form and plotted. Moreover, the beam root mean square (rms) width is also given in terms of one-dimensional integrals. The work presented can be used for assessing the utility of a BG beam for applications in emerging communication systems such as optical wireless communications (OWC).

Beam intensity and spectral coherence of Hermite-cosine-Gaussian rectangular multi-Gaussian correlated Schell-model beam in oceanic turbulence

The beam spreading and evolution behavior of a partially coherent, Hermite-cosine-Gaussian (HcosG) rectangular multi-Gaussian correlated Schell-model beam propagating in oceanic turbulence is studied. Analytical expressions for the cross-spectral density function, as well as the root mean square (rms) beam width and the spectral degree of coherence, are derived based on the extended Huygens-Fresnel principle. The HcosG rectangular multi-Gaussian correlated Schell-model beam exhibits a multi-lobe pattern at short propagation distances. The dependencies of the number, size, shape, and centroid of the lobes on displacement parameters, source size, order of field distribution, and displacement are investigated. As the propagation distance increases, the spectral coherence decreases, and the differences between the spectral coherence curves gradually diminish. Additionally, for HcosG rectangular multi-Gaussian correlated Schell-model beams, better propagation performance was found in oceanic turbulence with larger mean square temperature dissipation rate, smaller turbulent kinetic energy dissipation rate per unit mass of fluid, and larger relative strength of temperature and salinity fluctuation.

Data-Driven Diffraction Loss Estimation for Future Intelligent Transportation Systems in 6G Networks

The advancement of 6G networks is driven by the need for customer-centric communication and network control, particularly in applications such as intelligent transport systems. These applications rely on outdoor communication in extremely high-frequency (EHF) bands, including millimeter wave (mmWave) frequencies exceeding 30 GHz. However, EHF signals face challenges such as higher attenuation, diffraction, and reflective losses caused by obstacles in outdoor environments. To overcome these challenges, 6G networks must focus on system designs that enhance propagation characteristics by predicting and mitigating diffraction, reflection, and scattering losses. Strategies such as proper handovers, antenna orientation, and link adaptation techniques based on losses can optimize the propagation environment. Among the network components, aerial networks, including unmanned aerial vehicles (UAVs) and electric vertical take-off and landing aircraft (eVTOL), are particularly susceptible to diffraction losses due to surrounding buildings in urban and suburban areas. Traditional statistical models for estimating the height of tall objects like buildings or trees are insufficient for accurately calculating diffraction losses due to the dynamic nature of user mobility, resulting in increased latency unsuitable for ultra-low latency applications. To address these challenges, this paper proposes a deep learning framework that utilizes easily accessible Google Street View imagery to estimate building heights and predict diffraction losses across various locations. The framework enables real-time decision-making to improve the propagation environment based on users’ locations. The proposed approach achieves high accuracy rates, with an accuracy of 39% for relative error below 2%, 83% for relative error below 4%, and 96% for both relative errors below 7% and 10%. Compared to traditional statistical methods, the proposed deep learning approach offers significant advantages in height prediction accuracy, demonstrating its efficacy in supporting the development of 6G networks. The ability to accurately estimate heights and map diffraction losses before network deployment enables proactive optimization and ensures real-time decision-making, enhancing the overall performance of 6G systems.

Diffraction Losses of a Dielectric Open Resonator

Diffraction Losses of a Dielectric Open Resonator

Spreading properties of partially coherent multi-Gaussian Schell-model and modified Bessel-correlated vortex beams in anisotropic turbulent plasma

We investigate the propagation characteristics of partially coherent multi-Gaussian Schell-model (MGSM) and modified Bessel-correlated (MBc) vortex beams traveling in a turbulent plasma. Based on the extended Huygens-Fresnel principle, the cross-spectral density expressions for partially coherent MGSM and MBc vortex beams propagating through turbulent plasma were derived. The results show that the dark spot at the center of the partially coherent MGSM beams disappears in the low-coherence states and remains in the high-coherence states only. In contrast, the intensity of partially coherent MBc vortex beams exists in low- and high-coherence states and does not change during propagation in a weak turbulent plasma.