CALCULATION OF POLARIZATION LOSSES FOR HF COMMUNICATION CHANNEL (Part 1)

2021 ◽  
pp. 42-52
Author(s):  
M. M. Anishin ◽  
G. A. Zhbankov
Keyword(s):  
Numerical Modeling ◽  
Communication Channel ◽  
Radio Link ◽  
Communication Link ◽  
Energy Characteristics ◽  
Decameter Range ◽  
Input Parameters ◽  
Calculation Results

The article describes an algorithm for calculating polarization losses, which are one of the energy characteristics of a HF communication channel when planning radio link of various paths and arbitrary relative positions of the receiving and transmitting points. Using the proposed method, numerical modeling of this type of loss for a given set of input parameters of communication link in the decameter range has been carried out. Based on the calculation results, conclusions were drawn regarding the behavior of polarization losses under various conditions.

Numerical study of the aerodynamic and power characteristics of the cycloidal rotor, under incoming flow

2019 ◽  
pp. 25-34
Author(s):  
Александр Анатольевич Дектерев ◽  
Артем Александрович Дектерев ◽  
Юрий Николаевич Горюнов
Keyword(s):  
Flow Velocity ◽  
Numerical Study ◽  
Lift Coefficient ◽  
Simulation Method ◽  
Aerodynamic Characteristics ◽  
Incoming Flow ◽  
Ansys Fluent ◽  
Energy Characteristics ◽  
Power Characteristics ◽  
Calculation Results

Исследование направлено на разработку и апробацию методики численного моделирования аэродинамических и энергетических характеристик циклоидального ротора. За основу взята конфигурация ротора IAT21 L3. Для нее с использованием CFD-пакета ANSYS Fluent построена математическая модель и выполнен расчет. Проанализировано влияние скорости набегающего потока воздуха на движущийся ротор. Математическая модель и полученные результаты исследования могут быть использованы при создании летательных аппаратов с движителями роторного типа. This article addresses the study of the aerodynamic and energy characteristics of a cycloidal rotor subject to the influence of the incoming flow. Cycloidal rotor is one of the perspective devices that provide movement of aircrafts. Despite the fact that the concept of a cycloidal rotor arose in the early twentieth century, the model of a full-scale aircraft has not been yet realized. Foreign scientists have developed models of aircraft ranging in weight from 0.06 to 100 kg. The method of numerical calculation of the cycloidal rotor from the article [1] is considered and realized in this study. The purpose of study was the development and testing of a numerical simulation method for the cycloidal rotor and study aerodynamic and energy characteristics of the rotor in the hovering mode and under the influence of the oncoming flow. The aerodynamic and energy characteristics of the cycloidal rotor, rotating at a speed of 1000 rpm with incoming flow on it with velocities of 20-80 km/h, were calculated. The calculation results showed a directly proportional increase of thrust with an increase of the incoming on the rotor flow velocity, but the power consumed by the rotor was also increased. Increase of the incoming flow velocity leads to the proportional increasing of the lift coefficient and the coefficient of drag. Up to a speed of 80 km/h, an increase in thrust and power is observed; at higher speeds, there is a predominance of nonstationary effects and difficulties in estimating the aerodynamic characteristics of the rotor. In the future, it is planned to consider the 3D formulation of the problem combined with possibility of the flow coming from other sides.

NUMERICAL SIMULATION OF THE LIGHT AIRCRAFT PROPELLER NOISE UNDER STATIC CONDITION

Akustika ◽  
2021 ◽  
pp. 100-106
Author(s):  
sergey Timushev ◽  
Alexey Yakovlev ◽  
Petr Moshkov
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Numerical Modeling ◽  
Vortex Method ◽  
Static Condition ◽  
Semiempirical Model ◽  
Calculation Methods ◽  
Propeller Noise ◽  
Calculation Results ◽  
Static Conditions

The problem of simulation the noise generated during the operation of the propeller is considered. Calculation methods are described and numerical simulation of the noise of a light aircraft propeller by the acoustic-vortex method is performed. The results of numerical modeling of the tonal components of the propeller noise when operating under static conditions are compared with experimental data and calculation results based on a semiempirical model.

scholarly journals Enhancing the Performance of Medical Implant Communication Systems through Cooperative Diversity

2010 ◽  
Vol 2010 ◽  
pp. 1-10 ◽  
Author(s):  
Barnabás Hegyi ◽  
János Levendovszky
Keyword(s):  
Cooperative Communication ◽  
System Performance ◽  
Communication Systems ◽  
Communication Channel ◽  
Cooperative Diversity ◽  
Communication Link ◽  
Medical Implants ◽  
Medical Implant ◽  
Cardioverter Defibrillators ◽  
Implant Communication

Battery-operated medical implants—such as pacemakers or cardioverter-defibrillators—have already been widely used in practical telemedicine and telecare applications. However, no solution has yet been found to mitigate the effect of the fading that the in-body to off-body communication channel is subject to. In this paper, we reveal and assess the potential of cooperative diversity to combat fading—hence to improve system performance—in medical implant communication systems. In the particular cooperative communication scenario we consider, multiple cooperating receiver units are installed across the room accommodating the patient with a medical implant inside his/her body. Our investigations have shown that the application of cooperative diversity is a promising approach to enhance the performance of medical implant communication systems in various aspects such as implant lifetime and communication link reliability.

scholarly journals A new class of polyphase pseudo-random sequences with a nonlinear generation algorithm for secure radio communication link between unmanned vehicles and dispatch centers of the "smart city"

T-Comm ◽  
2020 ◽  
Vol 14 (8) ◽  
pp. 42-46
Author(s):  
Evgeniy M. Lobov ◽  
◽  
Dmitry N. Shubin ◽  
Nikolai A. Kandaurov ◽  
Elizaveta O. Lobova ◽  
...  
Keyword(s):  
Smart City ◽  
Communication Systems ◽  
Cross Correlation ◽  
Unmanned Vehicles ◽  
Radio Link ◽  
Communication Link ◽  
Generation Algorithm ◽  
Random Sequences ◽  
New Class ◽  
Nonlinear Generation

The article discusses an algorithm for generating a new class of polyphase pseudo-random sequences with a nonlinear generation algorithm for use in secure communication systems with spread spectrum technology. In particular, the proposed sequences are relevant to use for generating signals in a secure command radio link between unmanned vehicles located in different environments, and dispatch centers of the "smart city". An analysis of the existing ensembles and an assessment of their main characteristics are carried out. Namely, the size of the ensemble, which affects the security of the communication system, and the level of maximum emissions of the cross-correlation function. The existing ensembles of polyphase pseudo-random sequences do not simultaneously have satisfactory values of the considered indicators. Therefore, an urgent task is to develop an ensemble that finds a compromise between these two characteristics and has a nonlinear generation algorithm. The essence of the algorithm for the formation of the proposed new class of polyphase pseudo-random sequences is to expand the classical polyphase sequences, for example, Frank, Chu, or Milewski, which have good correlation properties, de Bruijn sequences with a large ensemble and a nonlinear formation algorithm. Comparative analysis of the proposed method for forming a class of polyphase sequences shows the advantage of its use. In particular, an improvement in cross-correlation characteristics and a significant increase in the size of the ensemble of new sequences compared to the original sequences are shown. These properties can be used to increase the structural secrecy of command radio links.

scholarly journals EMR: A new metric to assess the resilience of directional mmWave channels to blockages

2021 ◽  
Vol 2 (2) ◽  
pp. 47-60
Author(s):  
Fatih Erden ◽  
Ozgur Ozdemir ◽  
Ismail Guvenc ◽  
David W. Matolak
Keyword(s):  
Communication Systems ◽  
Communication Channel ◽  
Path Loss ◽  
Spatial Diversity ◽  
Line Of Sight ◽  
Communication Link ◽  
Weighted Sum ◽  
Channel Measurements ◽  
Angular Domain ◽  
Cosine Distance

Millimeter-wave (mmWave) communication systems require narrow beams to compensate for high path loss and to increase the communication range. If an obstacle blocks the dominant communication direction, alternative paths (directions) should be quickly identified to maintain reliable connectivity. In this paper, we introduce a new metric to quantify the Effective Multipath Richness (EMR) of a directional communication channel in the angular domain. In particular, the proposed metric takes into account the strength and spatial diversity of the resolved Multipath Components (MPCs), while also considering the beamwidth of the communication link and the blockage characteristics. The metric is defined as a weighted sum of the number of distinct MPC clusters in the angular domain, where the clustering of the MPCs is performed based on the cosine-distance between the dominant MPCs. For a given transmitter (TX) and receiver (RX) pair, the EMR is a single scalar value that characterizes the robustness of the communication link against blockages, as it captures the number of unique communication directions that can be utilized. It is also possible to characterize the blockage robustness for the whole environment by evaluating the spatial distribution of the EMR metric considering various different TX/RX locations. Using our proposed metric, one can assess the scattering richness of different environments to achieve a particular service quality. We evaluate the proposed metric using our 28 GHz channel measurements in a library environment for Line-of-Sight (LOS) and NLOS scenarios, and compare it with some other commonly used propagation metrics. We argue that EMR is especially informative at higher frequencies, e.g., mmWave and terahertz (THz), where the propagation attenuation is high, and directional Non-Light-of-Sight (NLOS) communication is critical for the success of the network.

scholarly journals Investigation of accuracy of rain-rate and rain-attenuation prediction models in satellite communications based on meteorological skills

MAUSAM ◽  
2021 ◽  
Vol 68 (4) ◽  
pp. 621-632
Author(s):  
MEHRAN BEHJATI ◽  
JIT SINGH MANDEEP ◽  
MAHAMOD ISMAIL ◽  
ROSDIADEE NORDIN
Keyword(s):  
Prediction Model ◽  
Rain Rate ◽  
Prediction Models ◽  
Satellite Communications ◽  
Rain Attenuation ◽  
Vital Role ◽  
Measured Data ◽  
Radio Link ◽  
Communication Link ◽  
Specific Prediction

Rainfall is a major destructive factor which severely reduces the quality and reliability of propagated signals in satellite communications. Hence, rain-attenuation prediction plays a vital role in the satellite radio link planning and engineering. The accuracy of the rain-attenuation prediction models depends on two things; (i) the accuracy of rain-rate information and (ii) the area of study. Therefore, selecting an appropriate rain-attenuation prediction model for a new site without having any specific prediction model and experimental measured rain-rate would be challenging. In this regard, this letter takes advantage of climatology skills to find an accurate model for such kind of areas. To do so, we study the Urmia-site (37.55° N, 45.1° E) and its communication link with the Eutelsat 25A (25.5° E), where there is no available experimental measured data and specific prediction models for that site. Therefore, based on the meteorological skills, the Yong-in site in South-Korea (37.43° N, 126.93° E) was chosen, as a homogeneous area with Urmia, which has available measured data of rainfall and rain-attenuation. Afterward, the most common used global prediction models are applied to Yong-in and the results are compared with the existing measurements. Consequently, the more accurate rain-rate and rain-attenuation prediction models are investigated and generalized to Urmia, which are the ITU-R P.837-5 model with 34% r.m.s. and the Joo-Hwan model with 18% r.m.s., respectively. Finally, the amount of rain-attenuation in different useful frequency bands (10-50 GHz) is investigated for Urmia by the Joo-Hwan model.

scholarly journals NUMERICAL CALCULATION OF STEEL-CONCRETE COMPOSITE BEAMS

2019 ◽  
pp. 175-184
Author(s):  
A. S. Krylov
Keyword(s):  
Experimental Data ◽  
Numerical Modeling ◽  
Concrete Beams ◽  
Crack Opening ◽  
High Strength ◽  
Composite Beams ◽  
Experimental Models ◽  
Vertical Displacements ◽  
Calculation Results ◽  
Opening Width

The paper presents a brief review of test experiments with models of steel-concrete beams made of high-strength concretes. The description is given to models and features of the applied materials. Numerical modeling and calculations are performed for steel-concrete beams. The modeling is performed in two versions: with and without the steel-concrete contact interaction. The calculation results are given numerically and graphically, and loads corresponding to the limiting bearing capacity, vertical displacements, crack opening width, height of the selected compressed zone are obtained. All parameters are evaluated and compared with the experimental data. Numerical and experimental models of destruction are compared. The obtained simulation and numerical results are compared.

scholarly journals Implementation of UAV Communication Channel Using Airborne Wide-Band Low-Element Antenna Arrays

2020 ◽  
Vol 6 (2) ◽  
pp. 39-44
Author(s):  
K. Korovin ◽  
S. Kuzmin
Keyword(s):  
Long Range ◽  
Antenna Arrays ◽  
Communication Channel ◽  
Wide Band ◽  
Antenna System ◽  
Communication Link ◽  
Compact Antenna ◽  
Cylindrical Antenna ◽  
Vivaldi Antennas ◽  
Long Range Communication

In this paper, we consider the the possibility of constructing a long-range communication link using a broadband low-element cylindrical antenna array based on Vivaldi antennas in 10 GHz band. A comparative analysis of the choice of emitters, optimization of the system according to the ratio of the number of elements and gain, and the assessment of overall characteristics are carried out. It is shown that the use of low-element cylindrical array allows one to obtain a compact antenna system with a gain of 13–16 dB, which allows one to construct a long-range communication channel.

scholarly journals Narrowband Interference Suppression in Wireless OFDM Systems

2009 ◽  
Vol 5 (1) ◽  
Author(s):  
Zlatka Nikolova ◽  
Georgi Iliev ◽  
Miglen Ovtcharov ◽  
Vladimir Poulkov
Keyword(s):  
Communication Systems ◽  
Multiple Access ◽  
Communication Channel ◽  
Digital Data ◽  
Communication Link ◽  
Narrowband Interference ◽  
Frequency Division ◽  
Ofdm Systems ◽  
Signal Distortions ◽  
Channel Distortion

Signal distortions in communication systems occur between the transmitter and the receiver; these distortions normally cause bit errors at the receiver. In addition interference by other signals may add to the deterioration in performance of the communication link. In order to achieve reliable communication, the effects of the communication channel distortion and interfering signals must be reduced using different techniques. The aim of this paper is to introduce the fundamentals of Orthogonal Frequency Division Multiplexing (OFDM) and Orthogonal Frequency Division Multiple Access (OFDMA), to review and examine the effects of interference in a digital data communication link and to explore methods for mitigating or compensating for these effects.

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