Multi-band SIW antenna with modulated metasurface at 5G frequency Priya Suresh Nair 1

Multi-band SIW antenna with modulated metasurface at 5G
Priya Suresh Nair 1
, Amalendu Patnaik 2
, M.V. Kartikeyan 3
Millimeter and THz Laboratory, Dept. of Electronics and Communiction Engineering, Indian Institute of Technology Roorkee, Roorkee-247667, Uttarakhand, [email protected], 2
[email protected], 3
[email protected]
Abstract — This paper proposes a multi-band SIW an-
tenna which is linearly polarized. The antenna consists of
a T-shaped radiator inscribed on the upper side of the
dielectric substrate. This radiator is responsible for multi-
band occurrence. The operating frequency is chosen to be
28 GHz, which is a valid selection for 5G applications.
An aperiodic modulated metasurface is employed as the
ground plane for the proposed antenna. Modulated MTS
is a great alternative to the metal ground as it enhances
the gain and subsequently the front to back lobe ratio
(FTBR) of the antenna. The substrate used is FR4 epoxy
with a thickness of 0.8 mm. The simulations are done using
ANSYS HFSS. Only simulated results are presented as the
antenna fabrication is under process.
Keywords —T-shaped radiator, multiband ,metasurface
(MTS), articial magnetic conductor (AMC)
The reason for increased researches in multi-band
antennas is due to the expeditious development of radar
and satellite communication systems. One of the most
prominent choices for the implementation of the multi-
band antennas is slot antenna. It offers various advan-
tages such as higher bandwidth, low prole, low cost
etc. among many other factors. 9,10,11,12 describe
latest developments and trends in the eld of broad-band
and multi-band antennas. Despite this, the main factor
that limits its performance is the bidirectional radiation
pattern it produces.
Substrate integrated waveguides (SIWs) or laminated
waveguides have replaced the conventional transmission
lines at high frequency millimeter wave communication.
Propagation characteristics and ease of construction are
the main reasons among many others due to which it
is suitable waveguide structure at very high frequencies.
Its physical construction consists of two metallic plates
sandwiching the dielectric substrate. The metallic plates
are connected through arrays of cylindrical metallic
grooves. The wave propagation in the structure is bound
between these two arrays of cylindrical vias. SIWs also
provide easy integration of planar circuits. Microsrtip
transition is used to excite the SIW structure. The
main reason foe choosing this over other techniques is low return loss, low insertion loss and also it provides
sufcient bandwidth for the desired purpose. Metallic grounds are conductive surfaces that act as
reectors. They reverse the phase of the reected EM
waves. They also support surface waves. These two
reasons are sufcient enough to prove the fact that
metallic grounds have deleterious effects on antenna
performance. By introducing special periodic patterns
on the conductive surface, its surface properties can
be altered provided the period of this texture is much
smaller than the wavelength of the EM wave. Various
applications of the modulated MTSs are listed in 4. The
proposed antenna uses its application to control surface
waves. Recent years have seen researchers working
on non-periodic MTSs. The periodicity is taken as a
constant on the aperture and the variation of impedance
is achieved by varying the geometry, thereby giving a
non-periodic MTS structure. 5G is one of the most sought after wireless technol-
ogy. The answer to increasing demand for efcient, high
speed and secular communication is 5G as it utilizes
the unexplored high frequency bands. In this paper, the
frequency band under consideration is 22-40 GHz. In section II the design of the proposed antenna is ex-
plained. In Section III, HFSS simulations and its results
are given. The conclusions drawn from the proposed
design and its simulations are given in Section IV.
A. Antenna Design The geometry and design parameters of the proposed
SIW antenna at 28 GHz is shown in Fig. 1. The design
consists of a single layer substrate of FR4 epoxy having
a relative permittivity (
r) of 4.4 and loss tangent (tan
) of 0.02 with a substrate thickness of 0.8mm. The
diameter(d) and pitch (p) values are chosen according
to 6,7,8 in order to ensure that leakage of power
is minimized. The diameter of the periodic metallic
via is chosen to be 0.8mm whereas the chosen pitch
value is 0.87mm. There is a tapered transition between
microstrip feed line and SIW. The tapering prole is
used to overcome the challenges of impedance matching

in a wide frequency range at millimeter-wave bands. The
combination of a tapered prole and SIW technology
is implemented 5. One of the several reasons that
has been standing out for the tapering prole to be
easily integrated is the exibility in the SIW design. The
optimized numerical values of all the design parameters
are given in table 1. Fig. 1: T-radiator SIW antenna
B. AMC unit cell The unit cell of the proposed modulated articial
magnetic conductor (AMC) is shown in Fig.2. It consists
of 3X3 array of circular patches of different radii. The
size of each square element of AMC is 3.1mm X
3.1mm. The reason for incorporating non-periodicity in
the AMC texture is the reduction in area with almost
same performance characteristics. Fig. 2: Geometry of AMC unit cell
C. Design of antenna with aperiodic modulated MTS The metallic ground of conventional antenna is re-
placed with 3X2 array of the above mentioned mod-
ulated aperiodic AMC or MTS unit cell. This AMC
surface does not allow the propagating surface waves within the frequency band of interest and hence im-
proves the antenna radiation characteristics. The proper-
ties of in-phase reection and non propagation of surface
waves lead to the replacement of conventional metallic
ground plane with modulated AMC. The constant radius
(0.6mm) circular patches on the ground plane below
the length of T-radiator is to ensure that the EM waves
reected by T-radiator is in phase with the incident ones. Fig. 3: T-radiator SIW antenna with with modulated
aperiodic AMC
TABLE I: Antenna design parameters Design parameters Numerical values
(mm) Substrate length (L) 17.5
Substrate width (W) 8.5
Substrate thickness (th) 0.8
Length of SIW (L
1) 3.6
Width of SIW (w
3) 6
Diameter of the vias (d) 0.8
Pitch (s) 0.87
Width variation of tapered section (w
2) 2.5 to 3
Length of rst part of T-radiator (L
3) 3
Length of second part of T-radiator (L
2) 6.5
Width of T-radiator (w
4) 1.5
Radii of circular patches (r
1, r
2, r
3) 0.15,0.3,0.45
Length of AMC unit cell (L
5) 3.1
Width of AMC unit cell (w
5) 3.1
A. Reection coefcient comparison From the graph, it can be clearly stated that the intro-
duction of modulated metasurface results in decreased
refelction loss . The multi-band occurrence is due to the
T-radiator etched on the upper side of the FR4 epoxy
B. Radiation pattern comparison Gain of the antenna without modulated MTS is about
3 dBi whereas gain of the proposed antenna with mod-
ulated MTS is 4.03 dBi. It is evident from the polar
plots that the increase in gain is about 1 dBi with the
replacement of conventional metal ground with modu-
lated aperiodic AMC or MTS. Therefore the proposed

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Fig. 4: Reection coefcient T-radiator SIW antenna
with and without AMC Fig. 5: E-plane radiation pattern comparison
antenna is an efcient radiator with decreased back lobe
and increased gain.
This work presents an antenna design that is easy to
fabricate and utilize at 5G frequency bands. The paper
mainly focuses on how the introduction of modulated
aperiodic metasurface (MTS) or AMC improves gain
of the antenna by 1 dBi and also enhances the FTBR
of the antenna when compared to the antenna with
metallic ground plane. This is clearly visible in the
radiation pattern simulated using HFSS as shown in
Fig. The presence of T-radiator in the antenna design is
responsible for multi-band and SIW along with tapered
microstrip feeding ensures low reection loss.
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