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\begin{document}

\title{Design and analysis of ultra-wideband decoupling structure based on
polarisation mismatch}



\author[1]{Jianpu Qiao}%
\author[1]{Weijun Wu}%
\author[1]{Xianliang Zeng}%
\author[1]{Hang Ji}%
\author[1]{Li Tao}%
\affil[1]{China Ship Development and Design Center}%


\vspace{-1em}



  
  \date{May 15, 2024}


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\selectlanguage{english}
\begin{abstract}
In this work, a polarization rotating surface is designed and analyzed
and applied to the decoupling of ultra-wideband antennas. A method of
using dual-size combined rings is proposed to expand the operating
bandwidth to 4.8GHz--18.2GHz, and the polarization conversion rate
within the entire bandwidth is higher than 99\%. Based on the principle
of polarization mismatch, placing the polarization rotating surface
between ultra-wideband antennas for decoupling can reduce the coupling
between antennas by an average of 20dB within the operating bandwidth.
Simulation and experimental results consistently prove its excellent
decoupling capabilities and ultra-wide operating bandwidth.%
\end{abstract}%



\sloppy


\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

Design and analysis of ultra-wideband decoupling structure based on
polarisation mismatch

Jianpu Qiao, Weijun Wu, Xianliang Zeng, Hang Ji,

and Li Tao*

\emph{}

\par\null\par\null

\emph{}

\par\null\par\null

This paper proposes a Polarized Rotating Surface (PRS) in which the
middle layer is composed of two orthogonal open resonant rings of
different sizes, which is also an innovation of this structure. This
structure can convert TE/TM waves into TM/TE waves orthogonal to them,
and the polarisation conversion efficiency remains above 99\% within the
bandwidth. Therefore, the decoupling method of this structure is
different from the traditional decoupling by blocking electromagnetic
wave propagation, and different from the introduction of additional
paths for neutralization and decoupling. Instead, polarisation isolation
is achieved by converting electromagnetic waves into their orthogonal
waves. Not only that, through electromagnetic simulation, the proposed
polarisation rotating surface can reduce the electromagnetic coupling
between two ultra-wideband horn antennas whose centers are 1 m apart in
the range of 5GHz \textasciitilde{}19GHz by an average of 20dB and a
maximum of 30dB. The final experimental results demonstrate that, within
the operating frequency band, this PRS can reduce the coupling between
ultra- wideband array antennas by an average of 20dB.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}

\emph{Structural design:} Transmissive polarisation converters usually
consist of a three-layer structure of a resonant structure array and two
layers of orthogonal metal wire grids above and below it {[}14{]}. This
structure is often called a quasi Fabry--P\selectlanguage{ngerman}érot-like cavity resonant unit
structure. The F-P cavity resonant unit structure can cause
electromagnetic waves to be reflected multiple times between multi-layer
dielectric plates and ultimately increase the amplitude of the
transmission coefficient. The metal wire grid can select electromagnetic
waves with different polarisation directions. Because the current
direction on the surface of the wire grid is distributed along its
direction, and the direction of the current on the metal surface is
perpendicular to the electric field in the space near it, only when the
polarisation direction of the planar electromagnetic wave is
perpendicular to the metal wire grid can it pass through the metal wire
grid.

The unit structure and specific structural parameters of the PRS in this
paper are shown in Figure 1. The unit is divided into three layers. The
front and rear are composed of orthogonal metal wire grids. In the
middle are two open resonant rings. It is worth noting that the two
resonant rings have different sizes and the opening directions are
orthogonal to each other. The three layers of metal are separated by two
dielectric layers. The metal patch is copper with a thickness of
0.018mm, the conductivity is 5.8×10-7 S/m, the material of the
dielectric layer is F4BM-2, the relative dielectric constant is 2.2, and
the loss tangent is 0.0015. Among them, the period of the unit is a, the
metal wire grid spacing is d1, the metal wire grid width is d2, the
outer diameters of the two middle open resonant rings are r1 and r2, the
ring widths are w1 and w2, and the opening sizes are t1 and t2, the
thickness of both dielectric layers is h.

\selectlanguage{english}\emph{Simulation results and analysis:} When the polarisation direction
of the incident electromagnetic wave (y-polarisation) is perpendicular
to the metal wire grid, periodic boundary conditions are used to
simulate the unit of the polarized rotating surface. The S parameters of
the polarisation rotation unit are shown in Figure 2. When there is only
a larger double-opening resonant ring in the middle layer of the
polarisation rotating surface, the operating bandwidth is 8GHz
\textasciitilde{}15GHz, and the relative bandwidth is 60.87\%. When
there is only a smaller double-opening resonant ring in the middle layer
of the polarized rotating surface, the operating bandwidth is 16GHz
\textasciitilde{} 18GHz, and the relative bandwidth is 11.76\%. But when
the two sizes of double-open resonant rings are placed orthogonally, as
shown in the figure, the operating bandwidth is 4.8GHz
\textasciitilde{}18.2GHz, and the relative bandwidth is 116.5\%. Through
the combination of double-open resonant rings of different sizes, the
structure can finally work effectively in an ultra-wide frequency band.
It is worth noting that in Figure 2 (c), the two sizes of rings must be
placed orthogonal to reduce coupling between the two rings.

The surface current distribution on the open resonant ring is shown in
Figure 3. At 6GHz, the current is fully coupled to the large loop,
indicating that at low frequencies, the polarisation conversion function
is mainly carried out by the large loop, and the small loop is almost
ineffective; At 12GHz, the surface current is mainly concentrated on the
large ring, and there is also partial coupling on the small ring. At
this time, the large and small rings work together, but rely more on the
large ring to complete polarisation conversion; At 18GHz, the surface
current on the small ring is higher, indicating that at high
frequencies, the polarisation conversion work is mainly carried out by
the small ring. The comparison of surface currents on these three double
open resonant rings confirms the reason why the polarized rotating
surface designed in this paper can operate in an ultra-wide frequency
band.

The efficiency of polarisation rotation can provide an intuitive
description of the performance of polarisation converters. Polarisation
rotation efficiency (PRE), also known as polarisation conversion rate
(PCR), is defined as the ratio of the transmitted cross-polarized
electromagnetic wave energy to the total transmitted energy {[}15{]}.
When the incident electromagnetic wave is y-polarized, the calculation
formula for PCR is:

In the formula, `T' represents the transmitted wave, and the subscript
`xy' represents that the electromagnetic wave is incident by the
y-polarized wave and transmitted by the x-polarized wave.

The advantages of the dual-size combination ring designed in this
article can also be demonstrated through PCR. From Figure 4, it can be
intuitively seen that the performance effect of the polarized rotating
surface can convert incident electromagnetic waves into their
cross-polarized waves in the range of 4.8GHz\textasciitilde{}18.2GHz,
with a conversion efficiency higher than 99\%. At the same time, when
only a small or large ring exists, only a portion of that frequency band
can be covered. It is interesting that the two PCR curves in the figure
coincidentally intersect and converge at the 16GHz frequency point,
which makes people marvel at the ingenuity of the dual size combination
ring design.

Comparison of the proposed PRS with the existing PRS is given in Table
2. The superiority of the proposed PRS is strongly demonstrated by its
relative bandwidth, PCR, and relative maximum wavelength thickness.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image8/image8}

\end{center}
\end{figure}

\emph{Experimental verification:} As is well known, vertically
polarized waves need to be received by antennas with vertical
polarisation characteristics, while horizontally polarized waves need to
be received by antennas with horizontal polarisation characteristics.
When the polarisation direction of the incident wave is inconsistent
with that of the receiving antenna, the received signal energy will
decrease, which means polarisation loss will occur. When the
polarisation direction of the receiving antenna is completely orthogonal
to the polarisation direction of the incident wave, for example, if a
horizontally polarized antenna is used to receive a vertically polarized
incident wave, the antenna will not receive the energy of the incident
wave at all. In this case, the polarisation loss is the maximum, which
is called complete polarisation isolation {[}16{]}. This section
conducts experiments based on the principle of polarisation mismatch.

Considering the issue of excessive computational complexity and long
simulation time when simulating array antennas, we used the horn antenna
as the ultra-wideband antenna for simulation. The simulation diagram and
simulation results are shown in Figure 5. Over the entire operating
frequency range, when PRS is placed between two horn antennas, the
coupling between the antennas decreases by an average of 20dB. From the
simulation results, it has been proven that the use of polarisation
mismatch principle for antenna decoupling is effective, and it has also
demonstrated the decoupling ability of the PRS designed in this paper in
ultra-wideband.

The processed sample is shown in Figure 6 (b), with a length and width
of 400mm and a thickness of 6mm. The medium is the F4BM-2 sheet with a
relative dielectric constant of 2.2. This experiment was conducted using
the free space method. The experimental scene is shown in Figure 6 (a).
The polarisation rotating surface is placed between coplanar array
antennas spaced 1m apart. Since a single pair of array antennas cannot
cover the entire frequency band, the experiment is divided into two
frequency bands: 6GHz \textasciitilde{} 12GHz and 12GHz
\textasciitilde{} 18GH. For the same reason, the experimental results
are also divided into two parts. Figure 7 is a schematic diagram of the
coupling comparison between array antennas before and after simulated
PRS. In the entire frequency band from 6GHz to 18GHz, PRS can reduce the
coupling of the array antenna by an average of 20dB. Since the antennas
used in the simulation are different from those used in the experiment,
the result curves are also inconsistent. However, from the perspective
of decoupling capability and decoupling bandwidth, it is very consistent
with the simulation results, which effectively proves the decoupling
capability of PRS between ultra-wideband antennas.

\emph{Conclusion:} Based on the principle of polarisation mismatch, a
PRS with polarisation conversion rate higher than 99\% was designed and
manufactured from the perspective of polarisation. Moreover, the
dual-size combined ring is cleverly used to extend the operating
bandwidth to an ultra-wide frequency band of
4.8GHz\textasciitilde{}18.2GHz. In this paper, the PRS is applied
between the ultra-wideband horn antenna and the array antenna. The
simulation and experimental results consistently prove its superior
performance in decoupling capability and operating bandwidth. In short,
this PRS provides a new perspective and method on how to decouple
ultra-wideband antennas.

References

1 Pendry J B, Holden A J, Robbins D J, et al. Magnetism from conductors
and enhanced nonlinear phenomena{[}J{]}. IEEE transactions on microwave
theory and techniques, 1999, 47(11): 2075-2084.

2 Xu H X. Research on the Mechanism of Metasurface Electromagnetic
Regulation and the Application of Functional Devices{[}M{]}. Beijing:
Science Press,2019:3-14

3 Wang G M, Cai T, Liang J G, et al. Design and Application of
Electromagnetic Superstructured Surface{[}M{]}. Beijing: National
Defense Industry Press,2020:2-15

4 Cui T J, Li L, Liu S, et al. Information metamaterial systems{[}J{]}.
Iscience, 2020, 23(8): 101403.

5 He Y, Pan Z, Cheng X, et al. A novel dual-band, dual-polarized,
miniaturized and low-profile base station antenna{[}J{]}. IEEE
Transactions on Antennas and Propagation, 2015, 63(12): 5399-5408.

6 Zou X J, Wang G M, Wang Y W, et al. An efficient decoupling network
between feeding points for multielement linear arrays{[}J{]}. IEEE
Transactions on Antennas and Propagation, 2019, 67(5): 3101-3108.

7 Gao D, Cao Z X, Fu S D, et al. A novel slot-array defected ground
structure for decoupling microstrip antenna array{[}J{]}. IEEE
Transactions on Antennas and Propagation, 2020, 68(10): 7027-7038

8 Li M, Jiang L, Yeung K L. Novel and efficient parasitic decoupling
network for closely coupled antennas{[}J{]}. IEEE Transactions on
Antennas and Propagation, 2019, 67(6): 3574-3585.

9 Yang X M, Liu X G, Zhou X Y, et al. Reduction of mutual coupling
between closely packed patch antennas using waveguided
metamaterials{[}J{]}. IEEE Antennas and Wireless Propagation Letters,
2012, 11: 389-391.

10 Yang F, Peng L, Liao X, et al. Coupling reduction for a wideband
circularly polarized conformal array antenna with a single-negative
structure{[}J{]}. IEEE Antennas and Wireless Propagation Letters, 2019,
18(5): 991-995.

11 Niu Z, Zhang H, Chen Q, et al. Isolation enhancement in closely
coupled dual-band MIMO patch antennas{[}J{]}. IEEE Antennas and Wireless
Propagation Letters, 2019, 18(8): 1686-1690.

12 Liu B, Chen X, Tang J, et al. Co-and cross-polarization decoupling
structure with polarization rotation property between linearly polarized
dipole antennas with application to decoupling of circularly polarized
antennas{[}J{]}. IEEE Transactions on Antennas and Propagation, 2022,
70(1): 702-707.

13 Farahani M, Pourahmadazar J, Akbari M, et al. Mutual coupling
reduction in millimeter-wave MIMO antenna array using a metamaterial
polarization-rotator wall{[}J{]}. IEEE Antennas and Wireless Propagation
Letters, 2017, 16: 2324-2327.

14 Grady N K, Heyes J E, Chowdhury D R, et al. Terahertz metamaterials
for linear polarization conversion and anomalous refraction{[}J{]}.
Science, 2013, 340(6138): 1304-1307.

15 Wang J, Shen Z, Wu W. Cavity-based high-efficiency and wideband 90\selectlanguage{ngerman}°
polarization rotator{[}J{]}. Applied Physics Letters, 2016, 109(15):
153504.

16 Jin M T. CST Antenna Simulation and Engineering Design{[}M{]}.
Beijing: Electronic Industry Press.2014: 89

17 Li Y, Zhang J, Qu S, et al. Ultra-broadband linearly polarization
manipulation metamaterial{[}J{]}. Electronics Letters, 2014, 50(23):
1658-1660.

18 Saikia M, Ghosh S, Bhattacharyya S, et al. Broadband polarization
rotator using multilayered metasurfaces{[}C{]}//2015 IEEE Applied
Electromagnetics Conference (AEMC). IEEE, 2015: 1-2.

19 X Wu, Application research based on metamaterial electromagnetic wave
modulation {[}D{]} Chongqing University, 2017.

20 Omar A A, Shen Z, Ho S Y. Multiband and wideband 90° polarization
rotators{[}J{]}. IEEE Antennas and Wireless Propagation Letters, 2018,
17(10): 1822-1826.

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