A Dual-Band Dual-Polarised Stacked Patch Antenna for 28 GHz and 39 GHz 5G Millimetre-Wave Communication

Abstract

Rapid developments in wireless communications demand an antenna that can operate at dual frequency bands in a compact size. In this work, a dual-band dual-polarised antenna is proposed for future 5G wireless communications that can operate at 28 GHz and 39 GHz 5G frequency bands. The proposed antenna is a stacked capacitive coupled patch antenna with bend parasitic elements having a dual-polarisation capability. The design principles and the antenna performance are discussed in detail. The antenna covers 25.75-30.25 GHz and 36.5-41.5 GHz and has a broad bandwidth in both the frequency bands. The proposed antenna element has a peak gain of 7.14 dBi in the lower band and 6.44 dBi in the higher band. The antenna element has a compact size of 3.8 mm × 3.8 mm × 1 mm making it suitable for implementation of antenna arrays in mobile devices.

Full text

A Dual-Band Dual-Polarised Stacked Patch Antenna
for 28 GHz and 39 GHz 5G Millimetre-Wave
Communication
Manoj Stanley1, Yi Huang1, Hanyang Wang2, Hai Zhou2, Ahmed Alieldin1, Sumin Joseph1, Chaoyun Song1 and
Tianyuan Jia 1
1 Department of Electrical Engineering and Electronics, University of Liverpool, Liverpool, UK, e-mail:
Manoj.Stanley@liv.ac.uk;Yi.Huang@liv.ac.uk; Ahmed.alieldin@liv.ac.uk;Sumin.joseph@liv.ac.uk; C.Song2@liverpool.ac.uk
Tianyuan.Jia@liverpool.ac.uk
2 Huawei Technology (UK) Co. Ltd, Reading, United Kingdom,
email: hanyang.wang@huawei.com;hai.zhou1@huawei.com
Abstract—Rapid developments in wireless communications
demand an antenna that can operate at dual frequency bands
in a compact size. In this work, a dual-band dual-polarised
antenna is proposed for future 5G wireless communications
that can operate at 28 GHz and 39 GHz 5G frequency bands.
The proposed antenna is a stacked capacitive coupled patch
antenna with bend parasitic elements having a dual-
polarisation capability. The design principles and the antenna
performance are discussed in detail. The antenna covers 25.75-
30.25 GHz and 36.5-41.5 GHz and has a broad bandwidth in
both the frequency bands. The proposed antenna element has a
peak gain of 7.14 dBi in the lower band and 6.44 dBi in the
higher band. The antenna element has a compact size of 3.8
mm × 3.8 mm × 1 mm making it suitable for implementation of
antenna arrays in mobile devices.
Index Terms—5G, dual-polarisation, mm-Wave, patch
antenna, phased array, smartphone.
I. INTRODUCTION
Recently, some researchers have developed phased
antenna arrays for 5G communication at millimetre-wave
frequency bands [1-4]. For 5G systems, 28 and 39 GHz
frequency bands are strong candidates and its suitability for
high data rate and low latency systems are being
investigated. Researchers are exploring different antenna
designs with a small footprint and wide bandwidth for dual-
band operation. On the other hand, dual-polarisation is also
preferred, as the antennas have the benefit of allowing two
signals, with different orientations, to be transmitted or
received on the same antenna and to counteract polarisation
mismatch.
Several new and existing dual-polarised designs have
been proposed in the previous studies [4-5]. However, the
existing dual-polarised antenna designs with dual-band
capabilities do not meet the 5G requirement. For example,
the design in [6] had a complex feeding mechanism and had
a narrow bandwidth of 2.5% at the lower band (LB) and
1.7% at the higher band (HB), thus it is not sufficient for 5G
applications, which typically require at least a 10%
bandwidth at both frequency bands. In addition, the complex
feed structure will distort the radiation pattern at mm-wave
frequencies. In [7], a single layer coaxial fed structure was
proposed which used reactance loading using stubs and slits
to obtain dual-band functionality. The design also suffered
from a narrow bandwidth of less than 1% at the LB and HB.
In [8], antenna design used capacitive feeding and CPW
feeding to obtain dual resonance. This design also suffered
from a narrow bandwidth (1% at LB and 2% at the HB).
However, the design offered excellent isolation of 25 dB
between the two dual polarised ports. In [9-10], the antenna
designs used slot coupled feeding and tuning stubs to achieve
dual resonance. This design had a wide bandwidth of 11.6%
at the LB and 10% at the HB, but used a complex feeding
mechanism and used air as the dielectric, which is not
practical. In [11], several stacked wideband antenna designs
with multiple feeds had been investigated to obtain dual-
band operation. However, these designs were complex and
used thick substrates, which were not practical for mobile
devices. In [17], a tri-band patch antenna was proposed with
high gain. However, the radiation pattern had a narrow
beam-width and did not provide a stable radiation pattern in
the operating frequency range.
This work discusses the design strategies that have been
used to overcome these limitations and to design a compact
dual-band dual-polarised stacked capacitive fed patch
antenna. The evolution of the design and the performance of
the antenna element is explained in Section II. The
performance of the antenna element is compared with the
state-of-the-art antenna designs in Section III. The
conclusions of this work are outlined in section IV.
II. ANTENNA ELEMENT DESIGN AND PERFORMANCE
A. Antenna Element Design
For future 5G systems, dual-band antennas of broad
bandwidth with bandwidth percentage of at least 10% is
required for each band. The prospective 5G frequency bands
are 26.5-29.5 GHz and 37-40.5 GHz [12-13].

A new architecture for millimetre-wave 5G antenna
based on Antenna-in-Package (AiP) technology is introduced
in Fig. 1 (a) which has been developed from the feeding
techniques in [14]. The dual-band operation is implemented
using the stacked patch antenna configuration with the
bottom patch designed for LB operation at 28 GHz and top
patch designed for HB operation at 39 GHz. Two feeds are
used for dual-polarisation capability. The capacitive feed
integrated with the bottom patch layer improves the
bandwidth. Four parasitic elements are added in the same
layer as the top patch to improve the bandwidth and isolation
in the HB. Rogers RT5880 (ε𝒓= 2.2) of size 10 mm × 10 mm
× 0.9 mm is used as the substrate for the AiP module. The
ground plane is the same size as the substrate. The feed lines
from the RFIC to the capacitive feed section is modelled as a
discrete port in CST Microwave Studio simulation. The
RFIC uses an RF phase shifter to provide progressive phase
shifts to each antenna element to implement array scanning
[15]. Each of the RFIC is powered using DC lines from a
digital IC [16].
(a)
(b)
Fig. 1. (a) Proposed Antenna-in-Package architecture (b) Proposed
design with overall dimensions of the top and bottom patch in mm (Rogers
RT5880 substrate is hidden).
The proposed antenna is a dual-polarised stacked
capacitive fed patch antenna with bend parasitic elements as
shown in Fig. 1 (b) and has an overall size of 3.8 mm × 3.8
mm × 0.9 mm. The bottom patch has an edge length of 0.27λ
at 28 GHz and the top patch has an edge length of 0.28λ at
39 GHz. The parasitic elements have a length of 0.32λ at
40.5 GHz. The feed locations are such that the TM10 and
TM01 orthogonal patch modes are effectively excited.
It has been demonstrated in previous work, that wide
band can be achieved using capacitive feeding which helps
to utilise thicker substrates to achieve wider bandwidth [4-5].
Hence, a dual-polarised capacitive fed patch antenna with
two feeds is used as the starting point for this design. The
dual-band resonance is obtained in the next step by stacking
two different patches each designed for the respective
frequency band as shown in Fig. 2. This gives the capability
to tune both the frequency bands independently.
Fig 2. The evolution of the proposed design.
After stacking the capacitive fed patch antenna, reactance
loading is implemented by removing the corner sections
from the bottom patch to tune the LB independently. This
also facilitates in the reduction of the bottom patch size due

to the increase in the length of the current path. In the next
step, tuning stubs are added to the top patch at the edges
adjacent to the feed to tune the HB independently by
adjusting impedance without having to change the actual
feed position. Another pair of tuning stubs is added to the top
patch edges opposite to the feeding position to fine tune HB
independently and reduce the cross-polar levels, which were
introduced due to the addition of the pair of tuning stubs
adjacent to the feeding location. Reactance loading and stub
loading enables independent control of both LB and HB. In
the next stage, reactance loading by cutting a circular slot in
the middle of the top patch is done to tune HB independently
and providing an additional degree of freedom for impedance
matching. By combining reactance loading and stub loading,
the bandwidth of both LB and the HB can be optimised to
get a broadband dual-polarised design.
However, the isolation between the orthogonal
polarization ports in the HB still needs improvement. This
isolation can be improved by adding parasitic elements along
the edges of the patch as an additional layer. The parasitic
elements, which are adjacent to the feeds, trap energy from
the feed, thereby, reducing the amount of energy leaked into
the orthogonally polarised feed. In addition, a new resonance
is created in the HB at 40 GHz due to the parasitic elements,
which helps to widen the bandwidth in the HB. In the final
stage, the parasitics are bent to reduce the overall area of the
antenna element to 3.8 mm × 3.8 mm. Bending the parasitic
elements also improves the isolation between adjacent
antenna elements when used in an array configuration due to
the reduction in magnetic coupling.
24 26 28 30 32 34 36 38 40 42
-30
-25
-20
-15
-10
-5
0
Reflection Coefficient (dB)
Frequency (GHz)
S11 bend parasitics
S21 bend parasitics
Fig. 3. Simulated S-parameters of the antenna element.
Fig. 4. Radiation pattern of antenna element at 28 GHz and 39 GHz.
B. Antenna Element Performance
The simulated reflection coefficient of the antenna
element is shown in Fig. 3. The results indicate a 10 dB
return loss over 25.75-30.25 GHz and 36.5-41.5 GHz, which
covers the required frequency bands.
A worst-case isolation of 17 dB and 15 dB is seen
between the two feeds of the dual-polarised patch antenna in
the LB and HB respectively. The antenna element has a total
efficiency above 90% and 86% in the LB and HB
respectively.
The radiation patterns of the two feeds of the proposed
antenna element at 28 GHz and 39 GHz are shown in Fig. 4.
The antenna element exhibits a stable broadside radiation
pattern with realised peak gains around 7.1 dBi and 6.15 dBi
for both the feeds at 28 GHz and 39 GHz respectively. The
slight tilt of the radiation pattern is due to the asymmetric
feed placement with respect to the square patch element.
Hence, the radiation pattern is slightly tilted towards the feed
position, as strong currents exist along the slot around the
feed in the lower band.
III. COMPARISON WITH STATE-OF-THE-ART ANTENNA
DESIGNS
In order to evaluate the achievements of the proposed
dual-band, dual-polarised antenna element with respect to
existing designs, the antenna element is compared with some
recently published mm-wave dual-band antenna designs as
shown in Table I.
TABLE I
COMPARISON OF PROPOSED ANTENNA WITH TWO
RECENT ANTENNA DESIGNS
The key parameters are bandwidth in the LB as well as
the HB, antenna size, antenna element gain in the LB as well
as the HB and the capability of supporting dual-polarisation.
Although there exist several dual-band dual-polarised
antenna designs for various other frequency bands and
applications, only the low profile antenna designs are chosen
for a fair comparison.
The proposed antenna element provides a peak gain of
7.14 dBi in the LB and 6.44 dBi in the HB, which is higher
Design
[12]
[13]
This
work
Frequency
Bands (GHz)
23-29
37-40.5
27.7-
28.15
36.7-38.9
25.7-30.2
36.5-41.5
Antenna Size
(mm3)
7.2 × 6.9 ×
0.127
20 × 5.5 ×
0.254
3.8 × 3.8
× 0.9
BWLB (GHz)
6
0.45
4.5
BWHB (GHz)
3.5
2.2
5
Gain LB (dBi)
4.58
5.2
7.14
Gain HB (dBi)
6.15
5.9
6.44
Polarisation
Single
linear
Single
linear
Dual
linear

than any other existing mm-wave low profile dual-band
antenna designs. The proposed antenna element is of low
profile and has a size of 3.8 mm × 3.8 mm × 1 mm. It
provides a wide bandwidth of 4.5 GHz in the LB and 5 GHz
in the HB with dual-polarisation capability.
IV. CONCLUSION
A stacked capacitive fed patch antenna with bent
parasitic elements has been proposed and designed for dual-
band, dual-polarised operation at 28 GHz and 39 GHz 5G
frequency bands. The addition of the parasitic elements
improved the bandwidth and isolation performance in the
higher band. The proposed antenna element provided a peak
gain of 7.14 dBi in the lower band and 6.44 dBi in the higher
band, which is higher than any other existing low profile
dual-band antenna design. It has a wide bandwidth of 4.5
GHz in the lower band and 5 GHz in the higher band with
dual-polarisation capability. The antenna design has a low
profile, occupied space of 3.8 mm × 3.8 mm × 1 mm, and is
a strong candidate for dual-band dual-polarised mm-wave
antenna array implementation in mobile phones.
REFERENCES
[1] W. Hong, K.H. Baek, Y. Lee, Y. Kim, and S. T. Ko, “Study and
Prototyping of Practically Large-Scale mmWave Antenna Systems
for 5G Cellular Devices”, IEEE Commun. Mag. , Sep. 2014.
[2] M. Stanley, Y. Huang, T. Loh, Q. Xu, H. Wang and H. Zhou, “A
High Gain Steerable Millimeter-Wave Antenna Array for 5G
Smartphone Applications”, Eur. Conf. Antennas and Propag., Paris,
Apr. 2017.
[3] M. Stanley, Y. Huang, H. Wang, H. Zhou, A. Al-Eiden and S.Joseph,
“A Capacitive Coupled Patch Antenna Array with High Gain and
Wide Coverage for 5G Smartphone Applications”, IEEE Access, vol.
6, pp. 41942 – 41954, Aug. 2018.
[4] M. Stanley, Y. Huang, H. Wang, H. Zhou, A. Al-Eiden and S.Joseph,
“A Novel mm-Wave Phased Array for 180 degree coverage for 5G
Smartphone Applications”, Eur. Conf. . Antennas and Propag.,
London, Mar. 2018.
[5] M. Stanley, Y. Huang, H. Wang, H. Zhou, A. Al-Eiden and S.Joseph,
“A Transparent Dual-Polarized Antenna Array for 5G Smartphone
Applications”, Int. Sym. Antenna Propag., Boston, Jul. 2018.
[6] B. Rohrdantz, et.al, “A Dual-Frequency and Dual-Polarised Patch
Antenna at Ka-Band”, Eur. Radar Conf., Sep. 2015.
[7] M. Ibraheam, et.al, “Dual-band Dual-polarised Stub-loaded Patch
Antenna for Robust GNSS Receivers”, Eur. Conf. Antenna Propag.,
Apr. 2016.
[8] D.H. Choi, et.al, “Dual-band and dual-polarised microstrip antenna”,
Elec. Lett., vol. 42 No. 2, Jan. 2016.
[9] T. W. Chiou, et.al, “A Compact Dual-Band Dual-Polarised Patch
Antenna for 900/1800-MHz Cellular Systems”, IEEE Trans.
Antennas Propag., vol. 51, no. 8, Aug. 2003.
[10] S. Soodmand, et.al, “Circular formed dual-band dual-polarised patch
antenna and a method for designing compact combined feed
networks”, Int. Jour. Elec. and Commun., Jun. 2010.
[11] Borja, et al, “Dual-Polarised Radiating Element, Dual-Band Dual-
Polarised Antenna assembly And Dual-Polarised Antenna Array”,
United States Patent, US 8,354,972 B2, Jan. 2013.
[12] O. Haraz, M. Mamdouh, M. Ali, A. Elboushi, A. Sebak, “Four-
Element Dual-Band Printed Slot Antenna Array for the Future 5G
Mobile Communication Networks”, Int. Sym. Antenna Propag., Jul.
2015.
[13] N. Ashraf, O. Haraz, M. Ashraf and S. Alshebeili, “ 28/38-GHz Dual-
Band Millimeter Wave SIW Array Antenna with EBG Structures for
5G Applications”, Int. Conf. . Information and Commun. Technol.
Res., Abu Dhabi, May 2015.
[14] W. Hong, K. H. Baek and S. Ko, "Millimeter-Wave 5G Antennas for
Smartphones: Overview and Experimental Demonstration," in IEEE
Trans. Antennas and Propag., vol. 65, no. 12, pp. 6250-6261, Dec.
2017.
[15] B. Sadhu, et.al, “A 28-GHz 32-Element TRX Phased-Array IC With
Concurrent Dual-Polarized Operation and Orthogonal Phase and Gain
Control for 5G Communications”, IEEE Jour. Of Solid-State Circuits,
vol. 52, no. 12, pp. 3373 – 3391, Dec 2017.
[16] B. Yu, K. Yang, C. Y. D. Sim and G. Yang, "A Novel 28 GHz Beam
Steering Array for 5G Mobile Device With Metallic Casing
Application," in IEEE Trans. Antennas and Propag., vol. 66, no. 1,
pp. 462-466, Jan. 2018.
[17] A. Abdelaziz and E. Hamad, “Design of a Compact High Gain
Microstrip Patch Antenna for Tri-Band 5G Wireless
Communication,” Frequenz Published online 07.09.2018.