scholarly journals Description of ionospheric disturbances observed by Vertical Ionospheric Sounding at 3 MHz

2014 ◽  
Vol 57 (1) ◽  
Author(s):  
James Arokiasami Baskaradas ◽  
Silvio Bianchi ◽  
Marco Pietrella ◽  
Michael Pezzopane ◽  
Umberto Sciacca ◽  
...  
Keyword(s):  
High Frequency ◽  
Multipath Propagation ◽  
Multipath Fading ◽  
Propagation Path ◽  
Small Scale ◽  
Ionospheric Disturbances ◽  
Radio Waves ◽  
Time Intervals ◽  
Spatial Level ◽  
Ionospheric Sounding

<p>High Frequency radio waves reflected by the ionosphere can provide a relevant amount of information within the composite received signal. The ionosphere is indeed a frequency dispersive, bi-refractive, absorbing medium, in which multipath propagation occurs due to disturbance on a varied time-spatial scale. On the time-spatial level of Small Scale Disturbances (SSD) the ionosphere dynamics, detectable by Vertical Ionospheric Sounding (VIS), is mainly dependent on wrinkled layers acting as multi-reflectors. The present paper discusses different aspects of the effects of multipath fading suffered by the wave along the propagation path and potentially associated with SSD. To achieve these objectives, a VIS campaign at a fixed frequency of 3.0 MHz was conducted at the ionospheric observatory in Rome (Latitude 41.8 N; Longitude 12.5 E), by collecting a series of measurements of the power variations in received echo signals recorded between two consecutive ionograms whose sounding repetition rate was set to 15 min. The obtained results show that: 1) the fading suffered by the wave follows either a Rayleigh trend or a Nakagami-Rice trend, or a mix of them, the mixed case being the most frequent (about 65 % of the analysed cases); 2) the predominant periodicities characterizing the power variation are less than 25 s; such values are compatible with the small scale ionospheric disturbances; 3) for all the 24 hours of the day the ionospheric reflector is pretty stable and for time intervals of 10-30 s the periods of stability occur with a percentage of occurrence ranging between 55% and 95 %; for time intervals of 190- 210 s the periods of stability occur instead with a percentage of occurrence ranging between 5% and 54 %.</p>

RUSSIAN HIGH-LATITUDE NETWORK OF OBLIQUE IONOSPHERIC SOUNDING

2021 ◽  
pp. 5-13
Author(s):  
D. D. Rogov ◽  
◽  
V. M. Vystavnoi ◽  
N. F. Blagoveshchenskaya ◽  
P. E. Baryshev ◽  
...  
Keyword(s):  
High Latitude ◽  
Communication Systems ◽  
Arctic Region ◽  
Small Scale ◽  
Radio Waves ◽  
Radio Communication ◽  
Remote Diagnostics ◽  
F Region ◽  
High Latitude Ionosphere ◽  
Ionospheric Sounding

The network for monitoring the high-latitude ionosphere by the method of oblique ionospheric sounding deployed in the Russian Arctic region is considered. The study describes the main results of operational data processing for studying the high-latitude ionosphere and determining the conditions for the optimum operation of radio communication systems and over-the-horizon radars in this region. The study demonstrates the potential of the network as a tool for the remote diagnostics of parameters of small-scale artificial ionospheric irregularities induced by powerful HF radio waves in the mid-latitude ionospheric F-region.

SIGNAL NOISE IMMUNITY IN ALAMOUTI SYSTEMS TAKING INTO ACCOUNT PARAMETERS OF MULTIPATH COMMUNICATION CHANNELS

2020 ◽  
Author(s):  
М.А. БЫХОВСКИЙ
Keyword(s):  
Wave Propagation ◽  
Radio Wave ◽  
Noise Immunity ◽  
Multipath Propagation ◽  
Communication Channels ◽  
Spatial Diversity ◽  
Propagation Path ◽  
Communication Line ◽  
Radio Waves ◽  
Physical Features

Представлен метод анализа системы Аламоути - простейшей системы MISO, в которой для устранения интерференции лучей, приходящих в место приема, на передающем конце линии связи применяются только две передающие антенны с определенным пространственным разнесением. Метод основан на рассмотрении физических особенностей распространения радиоволн и позволяет учесть конкретные характеристики многолучевых трасс распространения между передающей и приемной станциями. Система Аламоути позволяет уменьшить флуктуации уровня сигнала, поступающего на вход демодулятора, полностью или частично устраняя интерференцию приходящих на вход приемника лучей. Получены формулы, которые позволяют оценить необходимую для обеспечения требуемой надежности приема сигналов энергетику линии связи, влияние расположения передающих антенн по отношению к трассе распространения радиоволн (вдоль или поперек трассы), а также величину необходимого пространственного разнесения передающих антенн, при котором может быть обеспечена максимально возможная помехоустойчивость приема сигналов. The paper offers the method of analysis of the Alamouti system, the simplest MISO system in which at the transmitting end of the communication line only two transmitting antennas with a certain spatial diversity are used to eliminate the interference of the rays arriving at the receiving site. The method is based on the study of the physical features of radio wave propagation and allows taking into account the specific characteristics of multipath propagation paths between the transmitting and receiving stations. The Alamouti system allows the reduction of fluctuations in the level of the signal entering the input of the demodulator, completely or partially eliminating the interference of the rays coming to the input of the receiver. The paper offers formulas that allow us to estimate the energy of the communication line, necessary to ensure the required reliability of signal reception, the influence of the location of the transmitting antennas relative to the propagation path of the radio waves (along or across the track), as well as the amount of necessary spatial diversity of the transmitting antennas at which the maximum possible noise immunity of signal reception can be ensured.

scholarly journals Simulation of High-Frequency Rotational Motion in a Two-Dimensional Laterally Heterogeneous Half-Space

2021 ◽  
Author(s):  
Ivan Lokmer ◽  
Varun Kumar Singla ◽  
John McCloskey
Keyword(s):  
Wave Field ◽  
Half Space ◽  
High Frequency ◽  
Body Waves ◽  
Propagation Path ◽  
Small Scale ◽  
Two Dimensional ◽  
Engineering Structures ◽  
Background Medium ◽  
Body Forces

&lt;p&gt;The seismic waves responsible for vibrating civil engineering structures undergo interference, focusing, scattering, and diffraction by the inhomogeneous medium encountered along the source-to-site propagation path. The subsurface heterogeneities at a site can particularly alter the local seismic wave field and amplify the ground rotations, thereby increasing the seismic hazard. The conventional techniques to carry out full wave field simulations (such as finite-difference or spectral finite element methods) at high frequencies (e.g., 15 Hz) are computationally expensive, particularly when the size of the heterogeneities is small (e.g., &lt;100 m). This study proposes an alternative technique that is based on the first-order perturbation theory for wave propagation. In this technique, the total wave field due to a particular source is obtained as a superposition of the &amp;#8216;mean&amp;#8217; and &amp;#8216;scattered&amp;#8217; wave fields. Whereas the &amp;#8216;mean&amp;#8217; wave field is the response of the background (i.e., heterogeneity-free) medium due to the given source, the &amp;#8216;scattered&amp;#8217; wave is the response of the background medium excited by fictitious body forces. For a two-dimensional laterally heterogeneous elastic medium, these body forces can be conveniently evaluated as a function of the material properties of the heterogeneities and the mean wave field. Since the problem of simulating high-frequency rotations in a laterally heterogeneous medium reduces to that of calculating rotations in the background medium subjected to the (1) given seismic source and (2) body forces that mathematically replace the small-scale heterogeneities, the original problem can be easily solved in a computationally accurate and efficient manner by using the classical (analytical) wavenumber-integration method. The workflow is illustrated for the case of a laterally heterogenous layer embedded in a homogeneous half-space excited by plane body-waves.&lt;/p&gt;

scholarly journals Investigation of the parameters of traveling ionospheric disturbances using a chirp ionosonde

2021 ◽  
Vol 2131 (5) ◽  
pp. 052097
Author(s):  
F Vybornov
Keyword(s):  
Multipath Propagation ◽  
Experimental Studies ◽  
Vertical Motion ◽  
Ionospheric Disturbances ◽  
Radio Waves ◽  
Technical Parameters ◽  
Traveling Ionospheric Disturbances ◽  
The Village ◽  
The City ◽  
Nizhny Novgorod Region

Abstract This article presents the results of experimental studies of parameters of natural traveling ionospheric disturbances of “sickle” type observed at mid-latitudes using linear frequency modulation ionosondes. Technical parameters of the ionosondes used are given. Experiments were carried out on slightly inclined paths in the central part of Russia in 2015 - 2020 in the daytime. The transmitting station was located in the village of Vasilsursk, Nizhny Novgorod Region. Registration was carried out in the city of Nizhny Novgorod. Examples of ionograms obtained in the course of measurements with different structure of perturbations are given. Estimates of development times of disturbances and their frequency range have been made. The structure of the received signal is analyzed. Based on the results of a complex experiment using a network of synchronously operating ionosondes of the same type, the data obtained were analyzed and direction and magnitude of propagation velocity of the phase front of moving disturbance were determined. A possible mechanism for the imitation of one-way vertical motion of a traveling disturbance characteristic of the mid-latitude ionosphere is discussed within the framework of multipath propagation of radio waves.

Characterization of Artificial, Small-Scale, Ionospheric Irregularities in the High-Latitude F Region Induced by High-Power, High-Frequency Radio Waves of Extraordinary Polarization

2019 ◽  
Vol 59 (6) ◽  
pp. 713-725
Author(s):  
N. F. Blagoveshchenskaya ◽  
T. D. Borisova ◽  
A. S. Kalishin ◽  
T. K. Yeoman ◽  
Yu. A. Schmelev ◽  
...  
Keyword(s):  
High Power ◽  
High Latitude ◽  
High Frequency ◽  
Ionospheric Irregularities ◽  
Small Scale ◽  
Radio Waves ◽  
F Region

Reflection of high-frequency radio waves in inhomogeneous ionospheric layers

Radio Science ◽  
1985 ◽  
Vol 20 (3) ◽  
pp. 303-309 ◽  
Author(s):  
Kenneth Davies ◽  
Charles M. Rush
Keyword(s):  
High Frequency ◽  
Radio Waves

Letters: A digital high-frequency multipath propagation simulator

1978 ◽  
Vol 48 (3) ◽  
pp. 140
Author(s):  
J.D. Ralphs ◽  
W. Matley ◽  
R.E.H. Bywater
Keyword(s):  
High Frequency ◽  
Multipath Propagation

scholarly journals Modeling of Non-WSSUS Double-Rayleigh Fading Channels for Vehicular Communications

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Carlos A. Gutiérrez ◽  
J. J. Jaime-Rodríguez ◽  
J. M. Luna-Rivera ◽  
Daniel U. Campos-Delgado ◽  
Javier Vázquez Castillo
Keyword(s):  
Fading Channels ◽  
Communication Systems ◽  
Rayleigh Fading ◽  
Channel Model ◽  
Closed Form Solution ◽  
Multipath Fading ◽  
Rayleigh Distribution ◽  
Rayleigh Fading Channels ◽  
Small Scale ◽  
Time Frequency

This paper deals with the modeling of nonstationary time-frequency (TF) dispersive multipath fading channels for vehicle-to-vehicle (V2V) communication systems. As a main contribution, the paper presents a novel geometry-based statistical channel model that facilitates the analysis of the nonstationarities of V2V fading channels arising at a small-scale level due to the time-varying nature of the propagation delays. This new geometrical channel model has been formulated following the principles of plane wave propagation (PWP) and assuming that the transmitted signal reaches the receiver antenna through double interactions with multiple interfering objects (IOs) randomly located in the propagation area. As a consequence of such interactions, the first-order statistics of the channel model’s envelope are shown to follow a worse-than-Rayleigh distribution; specifically, they follow a double-Rayleigh distribution. General expressions are derived for the envelope and phase distributions, four-dimensional (4D) TF correlation function (TF-CF), and TF-dependent delay and Doppler profiles of the proposed channel model. Such expressions are valid regardless of the underlying geometry of the propagation area. Furthermore, a closed-form solution of the 4D TF-CF is presented for the particular case of the geometrical two-ring scattering model. The obtained results provide new theoretical insights into the correlation and spectral properties of small-scale nonstationary V2V double-Rayleigh fading channels.

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