Radiation of Ultra-Wideband (UWB) Signals
The radiation of short duration signals (or ultra-wideband – UWB signals) is significantly different from the long duration narrowband signals (see Table 1 below). Paper analyzed the processes in linear antennas and gives a physical interpretation these differences.
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Радіоастрономічний інститут НАН України
2002
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| Цитувати: | Radiation of Ultra-Wideband (UWB) Signals / I.J. Immoreev, A.N. Sinyavin // Радиофизика и радиоастрономия. — 2002. — Т. 7, № 4. — С. 389-393. — Бібліогр.: 3 назв. — англ. |
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irk-123456789-1223432017-07-03T03:03:22Z Radiation of Ultra-Wideband (UWB) Signals Immoreev, I.J. Sinyavin, A.N. The radiation of short duration signals (or ultra-wideband – UWB signals) is significantly different from the long duration narrowband signals (see Table 1 below). Paper analyzed the processes in linear antennas and gives a physical interpretation these differences. В статье анализируются процессы в линейных антеннах. Излучение сигналов короткой длительности (или сверхширокополосных) существенно отличается от излучения сигналов большой длительности (узкополосных). Приводится физическая интерпретация этих различий. У статті аналізуються процеси у лінійних антенах. Випромінювання сигналів короткої тривалості (або надширокосмугових) суттєво відрізняється від випромінювання сигналів з великою тривалістю (вузькосмугових). Наводиться фізична інтерпретація цих відмінностей. 2002 Article Radiation of Ultra-Wideband (UWB) Signals / I.J. Immoreev, A.N. Sinyavin // Радиофизика и радиоастрономия. — 2002. — Т. 7, № 4. — С. 389-393. — Бібліогр.: 3 назв. — англ. 1027-9636 http://dspace.nbuv.gov.ua/handle/123456789/122343 en Радиофизика и радиоастрономия Радіоастрономічний інститут НАН України |
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The radiation of short duration signals (or ultra-wideband – UWB signals) is significantly different from the long duration narrowband signals (see Table 1 below). Paper analyzed the processes in linear antennas and gives a physical interpretation these differences. |
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Article |
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Immoreev, I.J. Sinyavin, A.N. |
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Immoreev, I.J. Sinyavin, A.N. Radiation of Ultra-Wideband (UWB) Signals Радиофизика и радиоастрономия |
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Immoreev, I.J. Sinyavin, A.N. |
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Immoreev, I.J. |
| title |
Radiation of Ultra-Wideband (UWB) Signals |
| title_short |
Radiation of Ultra-Wideband (UWB) Signals |
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Radiation of Ultra-Wideband (UWB) Signals |
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Radiation of Ultra-Wideband (UWB) Signals |
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Radiation of Ultra-Wideband (UWB) Signals |
| title_sort |
radiation of ultra-wideband (uwb) signals |
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Радіоастрономічний інститут НАН України |
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2002 |
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http://dspace.nbuv.gov.ua/handle/123456789/122343 |
| citation_txt |
Radiation of Ultra-Wideband (UWB) Signals / I.J. Immoreev, A.N. Sinyavin // Радиофизика и радиоастрономия. — 2002. — Т. 7, № 4. — С. 389-393. — Бібліогр.: 3 назв. — англ. |
| series |
Радиофизика и радиоастрономия |
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2025-07-08T21:32:48Z |
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2025-07-08T21:32:48Z |
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1837116027783086080 |
| fulltext |
Radio Physics and Radio Astronomy, 2002, v. 7, No. 4, pp. 389-393
RADIATION OF ULTRA-WIDEBAND (UWB) SIGNALS
I.J. Immoreev, Senior Member IEEE, A.N. Sinyavin
Moscow Aviation Institute
Gospitalny val, Home 5, block 18, apt 314. 105094, Moscow, Russia,
E-mail: immoreev@aha.ru, asinyavin@fm-craft.ru
The radiation of short duration signals (or ultra-wideband – UWB signals) is significantly different from the
long duration narrowband signals (see Table 1 below). Paper analyzed the processes in linear antennas and gives
a physical interpretation these differences.
1. Introduction
The building of ultra-wideband (UWB) radars re-
quires a theoretical basis for calculating the antenna
design parameters and predicting the performance.
This is particularly important for designing antenna
systems that set up the performance of precision range
and the direction measuring systems. Recent publica-
tions about UWB antennas do not present a compre-
hensive and systematic theory for calculating such
antenna parameters. This is because the UWB signal
radiation process in antennas is significantly different
from the narrow-band signal case. Studying these
differences and determining the causes helps to de-
velop the design calculation methods for the UWB
antennas. In this paper, we analyzed the radiation pro-
cess occurring in linear UWB antennas and gave a
physical interpretation.
Table 1.
Signal Parameter
Narrowband UWB
Radiation All the aperture
of antenna (one
wave)
Only the center
and edges of
antenna’s aper-
ture (several
waves)
The form of a
radiation field
in time
Derivative from
form of current
(signal)
Repeats the form
of a current (sig-
nal)
Amplitude of a
radiation field
Depends on an-
gular coordi-
nates only
Depends on an-
gular coordinates
and time
The form of a
radiation field
in space (an-
tenna pattern)
Depends on an-
gular coordi-
nates only
Depends on an-
gular coordi-
nates, time and
on form of cur-
rent (signal)
Side radiation Side lobes Uniform de-
crease
2. The Processes in a UWB Antenna
2.1. A UWB Antenna Propagation Model
We consider a series excited antenna modeled as one
branch of a symmetrical radiator of length L , and
having a large number of the elementary radiators of
size L∆ . By examining the radiation from each ele-
ment L∆ we can sum up the results and provide the
far field estimate at different angles from the antenna
axis. The result shows that the field is a function of
time and the angular position from the antenna, in-
stead of the position, as in the narrowband case. For
the given radiator size L , the radiation becomes axial
for small values of cτ . As τ has increased increases
to a constant length, the pattern becomes normal to
the antenna axis.
Fig. 1 shows the l representing one branch of a
symmetrical radiator with length L consisting of a
large number of elementary radiators with the linear
size L∆ . In Fig. 1 we use the following notation:
jL∆ is the j -th elementary radiator, jL is its coor-
dinate, r is the distance to observation point M ;
Θ is the angle between the direction to observation
point and the antenna axis. The pulse of current starts
at point O which is the physical base of the antenna.
2.2. Derivation of the Equation
We consider the electromagnetic far-field, appearing
r
M
0 θ
jL
L∆
L-L
Fig. 1. The symmetrical radiator model for the
analysis
I.J. Immoreev, A.N. Sinyavin
390 Radio Physics and Radio Astronomy, 2002, v. 7, No. 4
as the pulse of current spreads along the radiator
branch. The current pulse feeding to point O excites
the first elementary radiator. The electromagnetic
field appearing in the far field at time /r c has the
following form:
( )
0 1 1
0
,
sin 1 cos ,
4
E t
Z d L r Li t L
c r dt c c
θ
θ θ
π
=
− − − ∆
where 0Z is the free space impedance; 0c is the ve-
locity of propagation of the current pulse in the radia-
tor. To simplify calculations hereinafter we assume:
0c c= .
In time /L c∆ the pulse of current enter the
second elementary radiator and excite it. The second
electromagnetic field is as in the equation as 1L is
changed to 2L .
As the current pulse moves along the branch it
sequentially excites each elementary radiator. To get a
clear physical knowledge we ignore the resistance and
radiation losses and assume that the load absorbs the
current pulse after exciting the last, or N -th radiator.
The far field after the excitation of all the elementary
radiators is as:
0
1
( , )
cossin ,
4
N
j j
j
E t
L r LZ d i t L
cr dt c c
θ
θθ
π
Σ
=
=
− − − ∆ ∑
Now we can examine the continuous antenna.
For this purpose we consider the length of the elemen-
tary radiator tending to zero 0L∆ → and the num-
ber of elementary radiators tending to infinity
N → ∞ . Then, in our equation the summation can
be changed to integration so that
( )0
0
( , )
sin cos .
4
L
E t
Z d L r Li t dL
cr dt c c
θ
θ θ
π
Σ =
− − −
∫
This equation describes the electric component of the
electromagnetic far field for symmetrical radiator
branch excited by arbitrary current.
The field is determined by the derivative of cur-
rent with respect to time and is formed by various
points of the radiator as the pulse moves along the
wire. In round brackets there is the expression which
determines the current time of the system in view of
this delay. We take the derivative of this time with
respect to dL , and have the opportunity to introduce
the replacement variable: cos 1dt dL
c
θ −= . As a
result we obtain the receive integral from the deriva-
tive function of the same variable, which is equal to
this function. Then:
( )
( )
( )
0
0
0
( , )
sin 1 cos
4 cos 1
sin 1 cos
4 cos 1
.
L
E t
Z L r Li tr c c
Z L r Li t
r c c
ri t
c
θ
θ θ
π θ
θ θ
π θ
Σ =
− =− −−
− − − −−
−
It is seen from this equation that the radiation of the
symmetrical radiator branch in far field is a sum of
two fields. One of which is radiated when the current
pulse enters the point of radiator excitation, and the
other at the moment when this pulse achieves the end
of the radiator. In literature this process is often ex-
plained as the radiation from the excitation point and
from the end of radiator. However, this interpretation
is not correct.
Let us consider the example: the field created by
radiator branch in the case when the exciting current
pulse has the Gaussian form shown by the solid line
in Fig. 2, and is expressed by
( ) ( )2exp 4 ti t τ = − ,
where τ is the duration of pulse on level 0,5.
This pulse creates the elementary radiator far
field determined by its derivative. The result is the
symmetrical bipolar pulse shown by the dotted line in
Fig. 2. Having substituted equations and performing
differentiation and integration, we obtain:
( )
( ) }
0
2
2
sin 1,
4 cos 1
cos
exp 4
exp 4 .
ZE t
r
L r Lt
c c
rt c
θθ π θ
θ
τ
τ
Σ = ×
−
− − − − −
− −
dt
tdI )(
t
)(tI
),(tI
dttdI /)(
Fig. 2. Gaussian pulse and its derivative
Radiation of Ultra-Wideband (UWB) Signals
Radio Physics and Radio Astronomy, 2002, v. 7, No. 4 391
2.3. The Fields and Antenna Patterns during
Radiation of a UWB Signal
We examine the far field formation for the case where
the branch length L greatly exceeds the pulse dura-
tion in the space cτ .
In Fig. 3 the fields exited by elementary radiators
jL in point M at the angle 90θ = ° are shown with
continuous line. These fields have the double polarity
and time delay relative to each other. The far field
result, at any angle and distance, is compensated by
the addition or subtraction of the fields from different
points along the radiator. There is the full compensa-
tion of the fields in the time interval t τ= and
/t L c τ= − . However, some part of the fields ex-
cited by the pulse of current at the initial and terminal
areas of the radiator branch remain uncompensated.
The sum of these remaining fields is shown in Fig. 3
with dotted lines. As a result the field created by the
radiator branch under L cτ consists of two parts,
as if they were connected with the point of excitation
and with the end of this branch.
This figure explains the apparently contradictory
shape of the radiated short pulse because the field
waveform follows the current instead of its derivative.
The degree of interaction and compensation be-
tween the elementary radiator fields depends on the
antenna length and pulse duration. If the pulse dura-
tion τ increases and the antenna length L remains
constant, then the time interval on which the compen-
sation of the fields occurs will become less. Finally,
under L cτ the compensation practically stops, as
shown in Fig. 4. The antenna radiates with the whole
aperture simultaneously.
With variations of the observation angle θ , the
distances from the observation point to each elemen-
tary radiator jL vary. As a result, the summation of
far-fields for these radiators occurs in various ways
and the form of the resulting field created by the ra-
diator branch varies as shown in Fig. 5. Thus, if angle
θ is reduced the amplitude of this field increases.
This occurs because more of the elementary radiator
fields do not fall into the compensation areas. The
field amplitude increases until it is influenced by the
multiplier sin θ , which defines the pattern of the ele-
mentary radiator. Note the radiation waveform
changes with the angle from the antenna.
Let us consider the pattern of the radiator branch.
For this, we use the above equations. Thus, the con-
sidered antenna pattern is non-stationary and depends
on the time of the current pulse in the antenna. This
pattern can be presented as a family of instant pat-
)90,( °=Σ θtE
)(1 tE
)(2 tE
)(tEN
t
)(tE
c
r
c
L
c
r +
Fig. 3. Fields excited by radiator branch when
L cτ
)90,( °=Σ θtE
)(1 tE
)(2 tE
)(tEN
t
)(tE
c
r
c
L
c
r +
Fig. 4. The fields excited by the radiator branch
when L cτ
)(tE
t
1t 2t 3t 7t0t 4t 5t 6t
°= 90θ
°= 75θ
°= 60θ
°= 45θ
°= 10θ
°= 15θ
°= 30θ
Fig. 5. Variations of the summation field in the far
zone for different angles
0 50 100 150 200 250 300 350 d
E
t0
t1
t2
t3
t4
t5
tmax
t0< t1<...< t5< tmax
Fig. 6. UWB radiator instantaneous field patterns
for Gaussian pulse excitation
I.J. Immoreev, A.N. Sinyavin
392 Radio Physics and Radio Astronomy, 2002, v. 7, No. 4
terns, each of which corresponds to the instantaneous
far field for some given waveform.
Fig. 6 shows the family of instant patterns in the
field ( )E θ for the Gaussian pulse exciting the radia-
tor branch when the radiator length exceeds the signal
spatial duration so that L cτ . As it can be seen
from Fig. 6, the pattern maximum changes its direc-
tion during the time of the radiated field existence. At
initial time this maximum is directed practically along
the antenna axis. As the current pulse moves, the pat-
tern shifts toward the antenna normal. The space pat-
tern width and maximum value decrease as the pattern
moves away from the axis.
The field pattern of time varying nature is diffi-
cult to use. We can determine a static pattern by aver-
aging the radiator far field over the time of its exis-
tence. Such pattern is called the energy pattern
( )W θ . The family of such patterns for different rela-
tionships between the length of radiator branch L and
the pulse duration in space cτ is shown in Fig. 7. The
expressions for the energy pattern of a wire antenna
are also given in Malek G.M. Hussain, Matthew
J. Yedlin [2] for various values /L cτ . When
L cτ< , this pattern coincides with the radiator
branch pattern. If τ is reduced and L is held con-
stant, the pattern shifts from normal position to the
antenna and grows narrower. At values of L cτ ,
radiation becomes axial, as if the impulse source radi-
ates directly into free space with no compensation
from the antenna length.
The series excited antenna was considered
above. We can obtain similar results for the parallel
antenna excitation. For this purpose it is necessary to
exclude from the equations term /L c determining
delay of a current’s pulse in the aperture. Fig. 8 and 9
show the instantaneous field patterns and energy pat-
terns for the Gaussian pulse excitation of UWB radia-
tor in this case.
3. Conclusion
In the conventional antenna theory, the radiated en-
ergy duplicates the exciting signal frequency and
waveform. By examining the impulse radiator case,
we find that the length of the antenna and the radia-
tion direction with respect to the antenna axis produce
different waveforms. Analyzing and predicting UWB
signal radiation require a new approach to considering
how electronic impulses interact and compensate in
the far field.
This paper suggests that if antenna length
L cτ , there will be a continuously varying signal
spectrum in off-axis directions.
This could provide a method for the direction
finding with respect to the antenna axis based on the
signal waveform.
References
1. I.J. Immoreev. “Ultra-Wideband Radar: new opportu-
nities, unusual problems, system features,” Proceeding
of Moscow State Technical University, №4, pp. 25-26,
December,1998.
2. I.J. Immoreev. “Main Features of UWB Radars and
Differences from Common Narrowband Radars.” In
book «Ultrawideband Radar Technology», Edited by
James D. Taylor, CRC Press, Boca Raton, London,
New Work, Washington, 2000.
0 50 100 150 200 250 300 350 degrees
L
cτ
=0.01
0.51550
W
Wmax
1
0,2
0,4
0,6
0,8
Fig. 7. Family of the simple radiator field patterns
for different ratios of L to cτ
-60 -15 -30 -15 0 15 30 45 d
E
60
t1
t0
t2
t3
t4
t4< t3< t2< t1< t0
Fig. 8. The UWB radiator instantaneous field pat-
terns for the Gaussian pulse and parallel antenna
excitation
0 45 90 135
degrees
L
cτ
=5
10
20
30
40
W
Wmax
1
0,2
0,4
0,6
0,8
180
Fig. 9. Family of the simple radiator field patterns
for different ratios of L to cτ for parallel antenna
excitation
Radiation of Ultra-Wideband (UWB) Signals
Radio Physics and Radio Astronomy, 2002, v. 7, No. 4 393
3. Malek G.M. Hussain, Matthew J. Yedlin. “Active Ar-
ray Bearnforming for Ultra-Wideband Impulse Radar,”
IEEE International Radar Conference RADAR 2000,
Alexandria, USA, May 8-12, 2000.
ИЗЛУЧЕНИЕ
СВЕРХШИРОКОПОЛОСНЫХ
СИГНАЛОВ
И.Я. Иммореев, А.Н. Синявин
В статье анализируются процессы в линейных ан-
теннах. Излучение сигналов короткой длительности
(или сверхширокополосных) существенно отличается
от излучения сигналов большой длительности (узкопо-
лосных). Приводится физическая интерпретация этих
различий.
ВИПРОМІНЮВАННЯ
НАДШИРОКОСМУГОВИХ СИГНАЛІВ
І.Я. Імморєєв, А.М. Синявін
У статті аналізуються процеси у лінійних антенах.
Випромінювання сигналів короткої тривалості (або над-
широкосмугових) суттєво відрізняється від випроміню-
вання сигналів з великою тривалістю (вузькосмугових).
Наводиться фізична інтерпретація цих відмінностей.
|