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1 INTRODUCTION
Both in marine [1] and space [2] applications, the
requirements for high antenna gains are dictated by the
need to limit the transmitter power and large ranges of
the communication or navigation system, including 5G
[3][5] and systems installed on HAPS platforms [6] and
in the ground component. Additionally, the platforms
on which such solutions are installed are in motion in
at least two axes. For this reason, antenna arrays are
used that allow for changing the direction of the main
radiation.
Other applications include GPS and alternative
systems, where it is important to make the receiver [4]
resistant to spoofing (mitigation) by controlling the
radiation antenna pattern (CRPA), i.e. using directional
beam-steering antennas to perform spatial filtering, i.e.
suppressing signals coming from all other directions in
the receiver system in relation to the angular range of
the useful signal.
In this paper, modifications to the antenna array
geometry are proposed to reduce the side-lobe levels
and increase the angular range. This is a continuation
of previous studies [10], in which The MPM was used
to model radio channels in [11][12] and the 3GPP
channel model [16] in [14][15]. Due to the numerical
complexity of the simulation tests of interference
between multiple antenna beams, an analysis of the
influence of interference from different directions on a
single beam was performed.
The required difference between the levels of the
main direction of antenna radiation and the side lobes
is obtained by appropriately setting the electrical
centers of elements or groups of elements and therefore
also by building an appropriate power supply
network. A small number of elements, e.g. 3 or 4,
allows for a range of about ±30 . Doubling the number
of elements allows for increasing the angular range by
half, which is also possible by tilting some elements
relative to the others and by using lenses.
In the case of a scenario where it would be necessary
to increase the gain of the antenna array using
converging lenses, the angular range would be
reduced, therefore, for X-band and higher frequencies,
while for S-band and lower frequencies, the total
number of elements in the array was reduced. The
Modified Cylindrical Antenna Array for Maritime
Applications
J. Stępień & L. Kachel
Military University of Technology, Warsaw, Poland
ABSTRACT: The article presents modifications of a cylindrical antenna array dedicated to a communication
system in marine ap-plications. The possibilities of spatial filtration were investigated by simulation to obtain low
sidelobe levels of the 20 dBc order. The results for different antenna elements were compared in terms of
frequency filtration for the broadband ones. The optimal characteristics of the antenna system were determined
taking into account the influence of the cross-ing level the each antennas radiation characteristics and the radius
of their position.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 19
Number 4
December 2025
DOI: 10.12716/1001.19.04.25
1268
results of calculations and simulations for different
antenna pattern models were compared. The
optimized parameters [9] of the antenna array allow for
obtaining the expected spatial filtration [7] at a level of
typically 17-20dBc, the minimum for multiplexing [8].
2 ANALYSIS OF ANTENNA ARRAY
The calculations were made for the circular array
constructed of eight sector antennas ( ), tube or patch,
working in the S-band, in one example 3.5 GHz,
uniformly spaced around a circle with radius r with a
spacing of 45 degrees. The analysis of array aimed at
determining the radius for which the antenna array
radiation pattern would be close to omnidirectional.
Figure 1. presents the structure of the analyzed system,
where:
– angle of the signal arrival in relation to the
reference direction of the antenna system, e.g.
relative to the north direction (N),
– angle of the antenna layout
2πN
=
,
Nn
dddd ,,,,
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– distances of the phase centers
of the respective antennas to the tangent wave front
in S point to the circle with r radius.
Analysis of the circular antenna array was
conducted under the following assumptions:
− electromagnetic wave reaching the antenna is flat
one,
− antennas are uniformly spaced around a circle,
− the reference is the antenna, which determines
north direction together with the geometric center
of the antenna system (in our case, it is antenna No.
1),
− width of the antenna directivity characteristics do
not change in the analyzed frequency band,
− minor lobes were omitted in the analysis.
Figure 1. Antenna array in Cartesian coordinate system
For analytical description of the wave front in the
adopted coordinate system, normal equation was used
for the straight line tangent to the circle in S point. In
this case, dn distance of n-th antenna with xn, yn
coordinates from the wave front is described by the
following expression:
( ) ( ) ( ) ( )
2π 2π
cos 1 cos sin 1 sin 1
n
d r n n
NN
= − + − −
(1)
The following expression describes An amplitude
and the temporary phase
n of the signal at the output
of n-th antenna:
( )
( )
2
sin sin 1
where
2
2
sin 1
0 where
2
t
on
t
n
n
a
n
N
A
a
A
n
N
−−
−
=
−−
−
(2)
Analysis of aforementioned relationship reveals
that the values of the signal amplitudes at the outputs
of the respective antennas depend on the angle of the
wave arrival, and signal phases depend on the radius
of the circle of the analyzed antenna arrays, which is
reflected in the relationship (1).
Based on relationship (2), the directivity
characteristics of the respective antennas, which
created the antenna array, were determined.
Evaluation of influence of changes in level in the
antenna characteristics crossing into the signal
parameters occurring at their outputs was obtained by
change in the width
of the radiation characteristics.
Figure 2. presents the directivity characteristics of the
antenna elements, which are crossing at the levels of –
2dB. Polar characteristics for second linear polarization
is similarly presented in Figure 4.
Figure 2. Polar directivity array elements characteristics
On the Cartesian characteristic, shown in Figure 3.
and Figure 5., the intersection points of the directional
characteristics of the elements of subsequent sectors
were marked. These points are more than 2dB below
the maximum gain level and, in angular terms, it is
about ±23 deg and in relation to these angles in
multiples of ±90 deg.
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Figure 3. Cartesian elements directivity characteristics
Figure 4. Polar characteristics second linear polarization
Figure 5. Cartesian elements directivity characteristics for
second linear polarization
Figure 6. and Figure 7. present the directivity
characteristics of the antenna array for both
polarization in the polar and Cartesian systems
respectively. Farfield characteristics for sector antenna
array was shown in Figure 8. and it is quite similar to
the characteristics of an omnidirectional antenna with
gain 2.8dBi. The difference in gain level is
approximately ±1dB.
Figure 6. Polar directivity antenna array characteristics
Figure 7. Cartesian array directivity characteristics
Figure 8. Multi-sector array farfield characteristics
The antenna array was built based on a modified
element which farfield and gain characteristics are
shown in Figure 9. and Figure 10. The changes
included not only increasing the gain by 3 dB but also
reducing the azimuth beamwidth to match the number
of sectors. For example, 90 degrees for 6 sectors and
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about 60 degrees for 8 sectors. The beamwidth can be
controlled by connecting elements, but this requires
increasing their number by two or more. The
bandwidth of each element has also been increased to
700MHz. The antenna element parameters are
summarized in Table 1.
In order to reduce the number of elements, circular
polarization was obtained from each element so that it
was not necessary to connect the elements with phase
shifting shown in Figure 11. The parameters of the
connected elements are shown in Figure 12. The gain
characteristics of a single element and a combination of
four are shown in the Figure 10. and Figure 13,
respectively. Circular polarization was obtained in one
element by exciting signals both linear polarizations.
Figure 9. Antenna element farfield characteristic
Figure 10. Polar gain characteristic of antenna element
Figure 11. 4 elements antenna farfield characteristic
Figure 12. S-parameters characteristics of elements
Figure 13. Polar gain characteristic of 4 antenna elements
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Table 1. The modified antenna element parameters
Parameter
Value
Unit
"Antenna element gain"
9.8
dBi
SLL
>-15
dB
"f" _"C"
3.5
GHz
WFS
<1.5
[--]
"Bandwidth"
>700
MHz
"3dB Beamwidth" Vertical
59
°
"3dB Beamwidth" Horizontal
360
°
Figure 14. presents the directivity of antenna sector,
consisting of 3 elements in column, depending on the
angle in elevation. For comparison, the Figure 16.
shows directivity for 7 elements in column. As
expected, it is possible to achieve larger angles up to
±45 degrees for 7 elements for not worse SLL levels in
this case >26dB. In practice, a better solution will be to
make two columns of 3 elements, one above the other,
set at a e.g. 60 deg. angle.
Figure 14. Directivity characteristic 3 elements column
Figure 15. Parameters characteristics of 3 elements array
Figure 16. Directivity characteristic 7 elements column
Figure 17. Parameters characteristics of 7 elements array
Figure 15. and Figure 17. show not only the
directivity characteristics depending on the angle but
also the side lobe level SLL for 3 and 7 antenna
elements in a column (array) respectively. calculations
were performed for 0.5 and 0.4 spacings and other
parameters contained in the Table 1. The characteristics
show that the practical SLL level that can be achieved
is 20 dB in the entire angular range of ±30 degrees for 3
elements in a column and in the range of ±45 degrees
for 7 elements. Regardless of the number of elements,
the best parameters are obtained in the angular range
of ±30 degrees, therefore, illuminating with additional
elements is a more effective solution compared to a
larger number of elements in the column.
Figure 18. shows the structure of the model of the
selected sector. In order to obtain a gain of
approximately 10dBi from each element, lenses can be
used due to the sharing of a screen by all elements
limiting directivity the connected radiators constitute
the central element of the column. Connecting the
middle elements allows to reduce the distance between
the electrical centers below 0.5 for elements whose
dimensions prevent closer proximity in order to reduce
the SLL to the minimum possible levels.
Figure 18. Antenna array 2x2 with and without holder
Figure 19. Antenna array 2x2 directivity without holder
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Figure 20. Antenna array 2x2 directivity with holder
The directional characteristics are shown in Figure
19. and Figure 20., respectively, without and with the
model housing and as expected, the level of back
radiation is lower with antenna array mounting. The
obtained SLL level of >-15dB can be improved by
increasing the gain of the antenna element to about
12dBi, but this will require increasing the number of
sectors to 12. Practical SLL levels that can be achieved
are from 17dB to 20dB.
Figure 21. Arrays 2x1x2 and 3x2x3 amplitude tapering
Figure 22. Array 2x1x2 directivity in angle range
Figure 23. Array 3x2x3 directivity in angle range
Figure 21. shows the model structure of connecting
adjacent sectors for a maximum of 3 rows and various
arrangements. The directional characteristics of arrays
2x1x2 and 3x2x3 are shown in Figure 22. and Figure 23.,
respectively. The advantage of the 3x2x3 arrangement
is the equalization of directivity levels for the entire
angular range but this comes at the cost of a higher
level of side lobes at maximum angles. Skillful
arrangement of element connections and tapering are
key for optimization.
Figure 24. Antenna array 3x3 amplitude tapering
Figure 25. Antenna array 3x3 directivity, Phi=90
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Figure 26. Antenna array 3x3 directivity, Phi=0
Figure 24. shows the model structure of connecting
adjacent sectors in the case of a larger number of rows
in the presented example of 5. The directional
characteristics of array 3x3x3 are shown in Figure 25.
and Figure 26. Apart from increasing gain, there are no
noticeable benefits in such an arrangement. The SLL
levels are slightly lower for larger angles. A more
effective solution is to use additional elements to
illuminate the maximum angles, not simultaneously
+30deg or -30deg. This allows effectively combine a
column of maximum four elements.
Figure 27. Three-row modified cylindrical antenna array
Based on the presented elements and antenna
arrays the model shown in Figure 27. was also
designed in addition to the model with one element in
the column. It is possible to control beams in columns
or rows of the array. Skillful element combinations
allow to achieve gain close to 20dBi level while
maintaining low sidelobe levels of 15dBc to 20dBc. The
small number of elements limits beam steering to an
angular range of ±30 degrees in elevation. Gain
adjustments are made by selecting the power levels of
the control signals.
Arranging elements in a zigzag pattern allows you
to double the number of columns but forces to reduce
the width of the beam from a single element. Changing
the beam width is also beneficial due to reducing the
level of coupling between elements. Due to the limited
space, greater gain can be achieved by using horns or
planar antennas with lenses. Further work will concern
the analysis of the feasibility of prototype mechanics,
not only with overlapping elements but also with
conformal ones. The power levels of the stimulating
signals will also be optimized.
3 CONCLUSIONS
Radiation characteristics of cylindrical antenna array
elements were calculated. A system of 8 elements with
one for each sector based on patch antennas was
designed. Electromagnetic simulations were
performed, which resulted in obtaining radiation
characteristics of the antenna array operating in the S-
band, consistent with the calculations performed. The
simulations with 3 and more elements in the array
columns were performed not only to increase the gain
of the antenna array but also to be able to control the
beam angle in each sector independently.
REFERENCES
[1] J. Stępień, “Localization Methods in MF and UHF Reserve
Radionavigation System”, NTSP, 2020.
[2] J. Stępień, “Review of S-band and X-band Antennas and
Filters for both Maritime and Space applications”, ISAP,
2021.
[3] D. Zmysłowski, P. Skokowski, K. Malon, K. Maślanka,
J.M. Kelner, “Naval Use Cases of 5G Technology”, 09
2023, TransNav 17(3):595-603.
[4] D. Zmysłowski, K. Kryk, J.M. Kelner, “Testing GNSS
receiver robustness for jamming” December 2023
”Aviation and Security Issues” 4(2):139–155.
[5] NTT DOCOMO, INC., “5G Evolution and 6G”, White
Paper, Version 5.0, 01/2023.
[6] Go Otsuru, Hiroyuki Tsuji, Ryu Miura, Jun Suzuki,
Yoshihisa Kishiyama, “Efficient Antenna Tracking
Algorithm for HAPS Ground Station in Millimeter-
Wave”, WPMC, 2022.
[7] Cezary Ziółkowski; Jan M. Kelner, “Angular Separation of
Channels in 5G System Multi-Beam Antennas”, ICMCIS,
2019.
[8] Jan M. Kelner; Cezary Ziółkowski, “Spatial Multiplexing
of Channels by Using Multi-beam Antenna System for 60
GHz”, PIERS, 2019.
[9] Kamil Bechta; Jinfeng Du; Marcin Rybakowski,
“Optimized Antenna Array for Improving Performance
of 5G mmWave Fixed Wireless Access in Suburban
Environment”, 5GWF, 2019.
[10] Jan M. Kelner and Cezary Ziółkowski, “Interference in
Multi-beam Antenna System of 5G Network”, IJET, 2020.
[11] Kamil Bechta, Cezary Ziółkowski, Jan M. Kelner and
Leszek Nowosielski, “Modeling of Downlink Interference
in Massive MIMO 5G Macro-Cell”, MDPI Sensors, 2021.
[12] Kamil Bechta, Jan M. Kelner, Cezary Ziółkowski and
Leszek Nowosielski, “Inter-Beam Co-Channel Downlink
and Uplink Interference for 5G New Radio in mm-Wave
Bands”, MDPI Sensors, 2021.
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[13] Jarosław Wojtuń,Cezary Ziółkowski and Jan M. Kelner,
“Modification of Simple Antenna Pattern Models for
Inter-Beam Interference Assessment in Massive Multiple-
Input–Multiple-Output Systems”, MDPI Sensors, 2023.
[14] Cezary Ziółkowski, Jan M. Kelner, “Antenna pattern in
three-dimensional modelling of the arrival angle in
simulation studies of wireless channels”, IET, 2017.
[15] Cezary Ziółkowski; Jan M. Kelner, “Statistical
Evaluation of the Azimuth and Elevation Angles Seen at
the Output of the Receiving Antenna”, IEEE Transactions
on Antennas and Propagation, 2018.
[16] ETSI TR 138 901 V18.0.0, “5G; Study on channel model
for frequencies from 0.5 to 100 GHz”, 2024.
