Reflection of the Ultra-Wideband Signals from Plasma Layers
This paper is concerned with the temporal distortion caused by the dispersion of ultra-wideband signals reflecting from linear and parabolic plasma layers. The magnitudes of the expected effects have been estimated for the various parameters of the plasma layers and sounding ultra-wideband signals....
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| Цитувати: | Reflection of the Ultra-Wideband Signals from Plasma Layers / L.F. Chernogor, O.V. Lazorenko // Радиофизика и радиоастрономия. — 2002. — Т. 7, № 4. — С. 431-434. — Бібліогр.: 4 назв. — англ. |
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nasplib_isofts_kiev_ua-123456789-1223532025-02-10T00:37:44Z Reflection of the Ultra-Wideband Signals from Plasma Layers Отражение сверхширокополосных сигналов от плазменных слоев Відбиття надширокосмугових сигналів від плазмових шарів Chernogor, L.F. Lazorenko, O.V. This paper is concerned with the temporal distortion caused by the dispersion of ultra-wideband signals reflecting from linear and parabolic plasma layers. The magnitudes of the expected effects have been estimated for the various parameters of the plasma layers and sounding ultra-wideband signals. The ultra-wideband signal distortions are calculated for reflection from the ionospheric plasma layers and their features are described. Рассмотрены дисперсионные искажения, которые возникают при отражении сверхширокополосных сигналов от линейного и параболического плазменных слоев. Оценены величины наблюдаемых эффектов при различных соотношениях параметров плазменного слоя и зондирующего сверхширокополосного сигнала. Рассчитаны величины и описан характер дисперсионных отражений сверхширокополосных сигналов при отражении от ионосферных плазменных слоев. Розглянуто дисперсійні спотворення, що виникають при відбитті надширокосмугових сигналів від лінійного та параболічного плазмових шарів. Оцінено величини ефектів, що спостерігаються, при різних співвідношеннях параметрів плазмового шару та зондуючого надширокосмугового сигналу. Розраховано величини та описано характер дисперсійних спотворень надширокосмугових сигналів при відбитті від іоносферних плазмових шарів. 2002 Article Reflection of the Ultra-Wideband Signals from Plasma Layers / L.F. Chernogor, O.V. Lazorenko // Радиофизика и радиоастрономия. — 2002. — Т. 7, № 4. — С. 431-434. — Бібліогр.: 4 назв. — англ. 1027-9636 https://nasplib.isofts.kiev.ua/handle/123456789/122353 en Радиофизика и радиоастрономия application/pdf Радіоастрономічний інститут НАН України |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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English |
| description |
This paper is concerned with the temporal distortion caused by the dispersion of ultra-wideband signals reflecting from linear and parabolic plasma layers. The magnitudes of the expected effects have been estimated for the various parameters of the plasma layers and sounding ultra-wideband signals. The ultra-wideband signal distortions are calculated for reflection from the ionospheric plasma layers and their features are described. |
| format |
Article |
| author |
Chernogor, L.F. Lazorenko, O.V. |
| spellingShingle |
Chernogor, L.F. Lazorenko, O.V. Reflection of the Ultra-Wideband Signals from Plasma Layers Радиофизика и радиоастрономия |
| author_facet |
Chernogor, L.F. Lazorenko, O.V. |
| author_sort |
Chernogor, L.F. |
| title |
Reflection of the Ultra-Wideband Signals from Plasma Layers |
| title_short |
Reflection of the Ultra-Wideband Signals from Plasma Layers |
| title_full |
Reflection of the Ultra-Wideband Signals from Plasma Layers |
| title_fullStr |
Reflection of the Ultra-Wideband Signals from Plasma Layers |
| title_full_unstemmed |
Reflection of the Ultra-Wideband Signals from Plasma Layers |
| title_sort |
reflection of the ultra-wideband signals from plasma layers |
| publisher |
Радіоастрономічний інститут НАН України |
| publishDate |
2002 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/122353 |
| citation_txt |
Reflection of the Ultra-Wideband Signals from Plasma Layers / L.F. Chernogor, O.V. Lazorenko // Радиофизика и радиоастрономия. — 2002. — Т. 7, № 4. — С. 431-434. — Бібліогр.: 4 назв. — англ. |
| series |
Радиофизика и радиоастрономия |
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| fulltext |
Radio Physics and Radio Astronomy, 2002, v. 7, No. 4, pp. 431-434
REFLECTION OF THE ULTRA-WIDEBAND SIGNALS
FROM PLASMA LAYERS
L.F. Chernogor, O.V. Lazorenko
Kharkiv V. N. Karazin National University
4, Svoboda Square, Kharkov, 61077, Ukraine
E-mail: Leonid.F.Chernogor@univer.kharkov.ua
This paper is concerned with the temporal distortion caused by the dispersion of ultra-wideband signals re-
flecting from linear and parabolic plasma layers. The magnitudes of the expected effects have been estimated for
the various parameters of the plasma layers and sounding ultra-wideband signals. The ultra-wideband signal dis-
tortions are calculated for reflection from the ionospheric plasma layers and their features are described.
1. Introduction
In the 90s of the 20th century, the ultra-wideband
(UWB) signals introduced in the 50–60s by Ken-
naugh, Moffatt, and Kosgriff began to find increas-
ingly wide application to different areas of science
and engineering.
For example, the UWB signals could be used for
remote radio sensing snow and ice covers, the radio-
location of subsurface targets, the communication
with immersed submarines, for super fast data traffic
in computer networks, etc.
The application of such signals to radiolocation
allows a range resolution of 0.1 m to be attained for a
pulse duration of 910τ −≈ s, the detection of tar-
gets with a special antiradar cover, e.g., manufac-
tured by using the “Stealth” technology, to be ac-
complished, and the data on non-coordinate informa-
tion on the target (form, size, etc.) to be inferred [1].
The UWB signals were suggested to apply to
remote radio sensing near-earth space in the middle
of the 90s of the 20th century [2].
The plasma environments, in particular the
Earth's ionosphere and magnetosphere, were ex-
pected to exert the main negative effect on UWB
radio wave propagation due to the dispersion. The
features and magnitudes of these distortions due to
the phase velocity dispersion, as well as the absorp-
tion and attenuation dispersions, are considered in
detail in [3] for different models of the UWB signals.
The radar equation necessary for calculating the
parameters of radio systems was updated for the case
of UWB signal applications [4].
2. Simulation of Reflection
The sounding signals are described by six simple
analytical UWB signal models in the time-domain,
which have been suggested in [3].
The reflected signals in the time domain are
represented by the relation
( )
( )( )( ) exp 4 ( ) 2
2
( )
r
r
E t
fS f i z f n f i ft i
c
Q f df
ππ π
∞
−∞
=
+ − ×∫
(1)
where ( )S f is the spectral density of the sounding
signal given by the complex function
( ) ( ) ( )0 exp 2S f E t i ft dtπ
∞
−∞
= −∫ ,
f is the frequency, t is time, c is the speed of light
in free space, ( )rz f is the altitude of reflection of
the harmonic with frequency f , which is determined
from the condition
( )( ), 0rn f z f = ,
( ),n f z is the index of refraction;
( )
( )
( )
( )
0
1 ,
rz f
r
n f n f z dz
z f
= ∫ ,
1,
( )
0,
pm
pm
f f
Q f
f f
≤= >
, (2)
and where pmf is the maximum plasma frequency of
the medium. The relation (2) expresses the fact that
the spectral components with pmf f> are not re-
flected from the plasma layer.
The index of refraction of the medium is given by
( )
2
2
21 pfn f
f
= − .
L.F. Chernogor, O.V. Lazorenko
432 Radio Physics and Radio Astronomy, 2002, v. 7, No. 4
The linear and parabolic plasma layers were
selected for describing the medium because they are
most frequently used for approximating the actual
profiles of the Earth's ionospheric electron density.
They are given by the following expressions.
For the piece-wise linear layer
( )
[ ] [ ]
2 2 2 ,
0, , 0, ,
p p pm
m
m pm
zf f z f
z
z z f f
= =
∈ ∈
where mz is the altitude of the piece-wise linear
layer maximum.
For the parabolic layer
( ) ( ) ( )
[ ] ( )[ ]
2max2 2
max
max min
min max max
1 ,
, , 0, ,
p p
p
z zf z f z
z z
z z z f f z
− = − −
∈ ∈
where minz is the height of the parabolic layer be-
ginning, maxz is the height of the peak density. In
our case, it is convenient to set min 0z = , and to
designate max mz z= , max( )p pmf z f= .
It is convenient to introduce the dimensionless
variables
0 0
0 0
, , , p p
t zT F f Z F f
c
τ τ
τ τ
= = = = ,
which are dimensionless time, frequency, distance,
and plasma frequency, respectively, and 0τ is the
finite time duration of the UWB signal.
The signal reflected from the piece-wise linear
layer can be represented as
( ) ( )
( )
) ( )
3
2
8exp
3
2 .
2
r m
p m
FE T S F i Z
F Z
i FT i Q F dF
π
ππ
∞
−∞
= +
−
∫
(3)
The signal reflected from the parabolic layer is
given by
( )
( )
( )
( )
( )
( )
( )
2 2
exp 2
ln 2 .
2
r
p m
m
p m
p m
p m
E T
F Z F
S F i FZ
FF Z
F Z F
i FT i Q F dF
F Z F
π
ππ
∞
−∞
=
− + ×
− + − +
∫
(4)
The integrals (3) and (4) are evaluated by nu-
merical methods.
To model the actual ionospheric plasma layer,
we set ( ) 10p mf z = MHz for the daytime iono-
sphere and ( ) 10p mf z = MHz for the nighttime
ionosphere, and 200mz = km in both cases.
3. Results of Model Calculations
In reflecting the UWB signal from a linear or para-
bolic plasma layer with a given maximum plasma
frequency ( )pm p mF F Z≡ , two different situations
are possible.
In the first of them, the condition max pmF F≤
is satisfied ( maxF is the maximum frequency of the
UWB signal spectral density), i.e., all spectral com-
ponents of the probing signal are reflected and re-
turned back. Then, if all of them are reflected at the
same range from the source, i.е. from the boundary
of the plasma layer ( min maxZ Z= ), the signal
changes insignificantly due to the phase changes of
the complex spectrum of the signal by /2π in the
process of reflection. Such a situation is shown in
Fig. 1 for 80pmF = . It can be seen that a bi-lobe
signal pattern ( 2µ → ) has transformed into a tri-
lobe one ( 1,33µ ≈ ). However, the reflected signal
remains ultra-wideband.
In the second situation, max pmF F> , part of the
UWB signal spectrum is not reflected from the
plasma layer, and does not return. As a result, the
more there are such components, the narrower the
signal spectrum becomes, and therefore, the more
reflected signal lobes occurs, the smaller the wide-
band index µ becomes, and the faster the reflected
signal ceases to be a UWB signal. In Fig. 1, this
process can be seen as pmF decreases.
Therefore, in practical applications of UWB
signals to remotely sounding the ionosphere, the sig-
nals with max pmF F≤ should be selected. It is
beneficial both from the point of view of decreasing
the distortion in reflected signals, and from the point
of view of energy conservation, since for
max pmF F> part of signal energy is wasted.
Consider separately the effect of dispersion dis-
tortion of the sounding signal arising exclusively
because of the fact that the different signal spectral
components are reflected at different ranges from the
source of the signal, i.e., the condition max pmF F≤
satisfied.
In Fig. 2, the dispersion distortions in the UWB
sounding signals are shown when it is reflected from
the model parabolic plasma layer. It is established that
the greater spectral component frequency is, the
greater path it travels up to the level of reflection and
back. Provided pmF is a constant, this results in an
increase in the dispersion distortion of the reflected
signal as mZ increases; in dimensional variables, this
corresponds to an increase in mz if ( )p mf z and 0τ
remain constant. The distortion is displayed in the ap-
Reflection of the Ultra-Wideband Signals from Plasma Layers
Radio Physics and Radio Astronomy, 2002, v. 7, No. 4 433
pearance of new lobes in the UWB signal, which re-
duces its wideband index; therefore, the signal gradu-
ally ceases to be ultra-wideband. The temporal dura-
tion of the signal also increases with increasing mZ .
As distinct from the dispersion distortions of
UWB signals arising during their propagation in the
dispersive plasma environments, in particular, in the
Earth's ionosphere [3], when, as the signal disperses,
the high frequency components propagate to the ris-
ing edge of the signal and the low frequency to the
falling edge of the signal, at reflection the opposite
picture is observed. Here the lower frequency com-
ponents appear closer to the signal rising edge and
those with the higher frequency to the falling edge.
We shall now consider the reflection of UWB
signals from a real ionospheric layer, for which the
parabolic plasma layer model is used with the men-
tioned above parameters. It is convenient to introduce
the parameter r that is equal to the ratio of the
maximum frequency, maxf , in the UWB sounding
signal spectral density to the plasma frequency at
parabolic layer peak
( )
max max
p m pm
f Fr
f z F
= = .
The dispersive distortions depend on the value of this
parameter: the greater this parameter r is, the greater
distortions are.
The range 0 1r< ≤ corresponds to the reflec-
tion of all spectral components from the plasma
Fig. 1. Probing signal in the time-domain ( ( )0E T )
and in the frequency domain ( ( )0S F ), and the re-
flected signal in the time domain ( ( )rE T ) and in
the frequency domain ( ( )rS F ) for different values
of the peak plasma frequency pmF
Fig. 2. Dispersive distortion of the probing UWB
signals (model 5) reflecting from the parabolic
plasma layer with various layer peak heights mZ .
The layer peak plasma frequency max 50pmF F= =
L.F. Chernogor, O.V. Lazorenko
434 Radio Physics and Radio Astronomy, 2002, v. 7, No. 4
layer, and for 1r > , part of them does not reflect,
and consequently, does not return to the source of the
sounding signal. The number of such components
grows with increasing r .
As a quantitative property of the distortion, we
shall use the relative signal lengthening 0/τ τ where
τ is the echo time duration. It is established that the
dispersive distortion of the sounding UWB signals
used for remotely radio sensing the Earth's iono-
sphere is essential.
When the UWB signal with 4
0 5 10τ −= ⋅ s is
reflected from the ionospheric plasma layer with
200mz = km and 10pmf = MHz, which corre-
sponds to the daytime ionosphere,
0/ 1 1000τ τ ÷∼ when 0.01 0.60r = ÷ . The
features of the distortion is shown in Fig. 3.
Use of the same UWB sounding signals in the
nighttime ionosphere, 10pmf = MHz, results in
0/ 1 225τ τ ÷∼ when 0.05 0.60r = ÷ . Similar
results are also obtained with other ionospheric mod-
els. Therefore, the effects are virtually independent of
UWB signal model.
4. Conclusions
1. As the UWB signals are reflected from the iono-
spheric plasma layers, significant dispersive dis-
tortion arises.
2. The features of this distortion differ from those
occurring during UWB signal propagation in the
Earth's ionosphere and magnetosphere.
References
1. L.Y. Astanin, A.A. Kostylev. Fundamentals of Ultra-
Wideband Radar Measurements, Radio and Commu-
nication, Moscow (1989) (in Russian).
2. O.V. Lazorenko, L.F. Chernogor. In Proc. of 4th Cri-
mean Conference and Exhibition “Microwave Tech-
nology and Satellite Reception”. Sevastopol: Weber.
pp. 123-124. (1994) (in Russian).
3. O.V. Lazorenko, L.F. Chernogor. Geomagnetism and
Aeronomy, Vol. 37, No. 6, pp. 80–90, (1997) (in Rus-
sian).
4. O.V. Lazorenko, L.F. Chernogor. Radiotekhnika. All-
Ukr. Sci. Interdep. Mag.. No. 103. pp. 31–34. (1997)
(in Russian).
ОТРАЖЕНИЕ
СВЕРХШИРОКОПОЛОСНЫХ
СИГНАЛОВ ОТ ПЛАЗМЕННЫХ СЛОЕВ
Л.Ф. Черногор, О.В. Лазоренко
Рассмотрены дисперсионные искажения, которые
возникают при отражении сверхширокополосных сиг-
налов от линейного и параболического плазменных
слоев. Оценены величины наблюдаемых эффектов при
различных соотношениях параметров плазменного
слоя и зондирующего сверхширокополосного сигнала.
Рассчитаны величины и описан характер дисперсион-
ных отражений сверхширокополосных сигналов при
отражении от ионосферных плазменных слоев.
ВІДБИТТЯ НАДШИРОКОСМУГОВИХ
СИГНАЛІВ ВІД ПЛАЗМОВИХ ШАРІВ
Л.Ф. Чорногор, О.В. Лазоренко
Розглянуто дисперсійні спотворення, що виника-
ють при відбитті надширокосмугових сигналів від лі-
нійного та параболічного плазмових шарів. Оцінено
величини ефектів, що спостерігаються, при різних
співвідношеннях параметрів плазмового шару та зон-
дуючого надширокосмугового сигналу. Розраховано
величини та описано характер дисперсійних спотво-
рень надширокосмугових сигналів при відбитті від
іоносферних плазмових шарів.
Fig. 3. Dispersive distortion of the sounding UWB
signals reflecting from the parabolic ionospheric
layer with various values of r and for
4
0 5 10τ −= ⋅ s, 10pmf = MHz, 200mz = km
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