A novel design of antenna for the 3G mobile devices

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A novel design of antenna for the 3G mobile devices. This paper proposes a novel structure of the inverted F antenna based on meandering and folding methods for the monopole antenna placed on FR4 dielectric plate. The proposed antenna has compact size (21 mm × 14 mm × 3.2 mm). Moreover, this antenna still offers enough wide bandwidth (VSWR ≤ 2), which covers 3G bandwidth. Using the simulation program to optimize antenna structure and calculate the antenna parameters in order to verify its applicability for the 3G mobile devices.
VNU Journal of Science: Comp. Science & Com. Eng., Vol. 31, No. 2 (2015) 8-14
A Novel Design of Antenna for the 3G Mobile Devices
Ha Quoc Anh*, Nguyen Quoc Dinh
Department of Fundamentals of Radio and Electronic Engineering,
Le Quy Don Technical University, Hanoi City, Vietnam
Abstract
This paper proposes a novel structure of the inverted F antenna based on meandering and folding methods for the
monopole antenna placed on FR4 dielectric plate. The proposed antenna has compact size (21 mm × 14 mm ×
3.2 mm). Moreover, this antenna still offers enough wide bandwidth (VSWR 2), which covers 3G bandwidth.
Using the simulation program to optimize antenna structure and calculate the antenna parameters in order to
verify its applicability for the 3G mobile devices.
© 2015 Published by VNU Journal of Science.
Manuscript communication: received 04 May 2014, revised 29 April 2015, accepted 25 June 2015
Corresponding author: Ha Quoc Anh, haquocanh1812@gmail.com
Keywords: 3G, Inverted F Antenna, Miniaturization of Antenna.
1. Introduction
printed inverted F antenna structure for terminal
Nowadays, with the rapid growth of
wireless means of communication, there is a
growing demand for mobile devices that are
small, thin, attractive, lightweight, and curvy.
To satisfy the above demand, it is necessary to
miniaturize mobile device’s components.
Especially, antenna, an essential part, is
miniaturized in order to put into the device.
Many studies and suggestions about typical
antenna structure for portable devices have been
published recently. D. Bonefacic [1] proposed a
design for a micro-strip antenna that works on
central frequency of 2.0 GHz and has very
small size (30 mm × 12.9 mm × 5 mm) but the
bandwidth of the proposed antenna is too
narrow (26 MHz). Y. Kim [2] proposed a
folded loop antenna system for new future
handsets. M. Karaboikis [3] proposed a dual-
devices. K. Sarabandi [4] proposed a method of
miniaturized size antenna as small as 0.05λ ×
0.05λ. M. Akbari [5] presented an approach to
optimize the antenna structure by creating a
planar inverted F antenna (PIFA). However, the
overall size of the proposed antennas in the
references is still quite large; therefore it is
difficult for the mobile device to miniaturize its
size for applications in MIMO system. In order
to overcome the said shortcomings, in the
reference document [6], an antenna with smaller
size (23 mm × 14 mm × 5 mm) is proposed which
can be applied for 3G mobile devices.
In this paper, the authors use Ansoft HFSS
software to miniaturize antenna structure for the
3G mobile devices based on meandering and
folding methods for the monopole antenna,
which is developed from the inverted F
H.Q. Anh, N.Q. Dinh / VNU Journal of Science: Comp. Science & Com. Eng., Vol. 31, No. 2 (2015) 8-14
9
antenna.
Next,
we
analyze
the
inverted
F
 The input impedance of the antenna can
antenna placed on a metallic plane representing
reach 50 at the central frequency (to match
a mobile device. Then, it is possible to propose
perfectly with the feeder);
a method to miniaturizing antenna structure and
to design a compact antenna with dimensions of
21 mm × 15 mm × 3.2 mm, which is smaller
than antennas in the reference [6]. Although its
 VSWR 2;
 The bandwidth of the antenna is large
enough: (10%, 200 MHz).
height is only 3.2 mm but its bandwidth and
other technical parameters are still ensured.
2.2. A method of miniaturizing antenna structure
This antenna structure can be placed into thin
Let’s
consider
the
inverted
F
antenna
mobile devices.
placed
on
a
metallic
plane
(using
copper),
In order to match the antenna input
impedance with the feeder and to ensure its
bandwidth must be wide enough to cover the
3G bandwidth, the antenna structure is
optimized. Finally, the antenna parameters such
as input impedance, VSWR, radiation pattern
are calculated to validate the applicability of the
proposed antenna in 3G devices.
with dimensions of 86 mm × 40 mm × 0.1
mm, that represents a mobile device, with
surveyed bandwidth from 1.8 GHz to 2.2
GHz. A FR4 dielectric plate is placed
between the antenna and the metallic plane.
In Fig. 1, the dimension of the FR4 dielectric
plate is 40 mm × 15 mm × 3.2 mm. In order
to miniaturize the size of the initial inverted F
antenna, it is possible to apply meandering,
folding and slotting methods [7] and apply
2. The proposed antenna structure for 3G
dielectric substance FR4 to form its structure.
mobile devices
In
addition, in
order
to
ensure
the
antenna
2.1. Main requirements
mobile devices
of
antennas
for
3G
input impedance, it is needed to change the
current in the antenna by varying the distance
between the feeding point and the grounding
When design an antenna for the mobile
devices, bandwidth and the requirements of
point and adding U,
rectangular strip-lines.
L
shape
strip-lines,
antenna compact dimensions must be taken into
Compared
with
the
initial
inverted
F
account. Normally, the 3G mobile devices have
the length, width and thickness of 110 mm, 60
mm, and 12 mm, respectively. Currently, the
3G mobile systems in Vietnam use frequencies
from 1.9 GHz to 2.17 GHz. Thus, the design
antenna for 3G mobile devices has to ensure the
requirements on compact size, bandwidth and
several following parameters:
 The antenna size must be small enough to
be placed in a mobile device, its height is less
than 5 mm, its length and its width are less than
40 mm;
antenna structure, the proposed antenna has a
U-shape strip-line with the parameter of s and
two rectangular strip-lines with the parameters
of l1 × l2 and l6 × l7, as shown Fig. 2. Adding
these strip-lines will change the current
distribution on the antenna. This in turn will
change the antenna input impedance and
therefore help the impedance matching with
the feeder. Moreover, the optimized antenna
will expand the bandwidth and ensure more
compact size.
w
l
l
l
w
l
l
l
l
l
w
10
H.Q. Anh, N.Q. Dinh / VNU Journal of Science: Comp. Science & Com. Eng., Vol. 31, No. 2 (2015) 8-14
mm
(length),
14
mm
(width),
and
3.2
mm
(height). A gap between the feeding point and
Antenna
the grounding point is l5 = 9 mm. Except for the
strip-lines are connected to the metallic plane,
other strip-lines are fixed on the dielectric FR4
L
plate and parallel to the ground.
To choose the optimal parameters
of
antenna as shown in Table I, we examine of the
effect of antenna size parameters to VSWR.
Ground plane
2.3. Impact of VSWR when changing antenna
size parameters
W
2.3.1. Impact of VSWR when changing l3
Fig. 1. The antenna structure.
2.0
3G bandwidth
(270 MHz)
After
many
experiments,
an
optimized
antenna
structure
is
chosen.
The
size
of
the
optimized antenna elements is shown in Table I.
1.5
1
7
8
3
3
2
1
1.0
1.80
1.85
l3 = 14.5 mm
l3 = 14.0 mm
l3 = 13.5 mm
1.90 1.95 2.00 2.05 2.10
Frequency [GHz]
2.15
2.20
z
h
6
s
5
4
2
Fig. 3. The effect of l3 to VSWR.
The results of calculating the dependence
x
of parameter l3 on the VSWR is represented
in Fig. 3. For VSWR 2, when increasing the
y
Feedingpoint Groundingpoint
length l3, the electrical length of monopole
antenna increases so that resonance frequency
and
bandwidth
of
antenna
decrease.
In
Fig. 2. The structure of proposed antenna.
contrast,
when
reducing
the
length
l3,
the
Antenna is connected with the metallic
plane by 2 points, the feeding point and the
grounding point. This antenna structure
consists of copper strip-lines of width w2 = 1
mm, thickness is 0.1 mm. The overall
bandwidth of antenna increases but it does
not cover the bandwidth of 3G mobile
devices. As a result, in order to have
bandwidth of antenna cover the working
bandwidth of 3G mobile devices, it is
dimensions of the antenna are chosen with 21
necessary to select parameter l3 = 14.0 mm.
VSWR
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A novel design of antenna for the 3G mobile devices. This paper proposes a novel structure of the inverted F antenna based on meandering and folding methods for the monopole antenna placed on FR4 dielectric plate. The proposed antenna has compact size (21 mm × 14 mm × 3.2 mm). Moreover, this antenna still offers enough wide bandwidth (VSWR ≤ 2), which covers 3G bandwidth. Using the simulation program to optimize antenna structure and calculate the antenna parameters in order to verify its applicability for the 3G mobile devices..

Nội dung

VNU Journal of Science: Comp. Science & Com. Eng., Vol. 31, No. 2 (2015) 8-14 A Novel Design of Antenna for the 3G Mobile Devices Ha Quoc Anh*, Nguyen Quoc Dinh Department of Fundamentals of Radio and Electronic Engineering, Le Quy Don Technical University, Hanoi City, Vietnam Abstract This paper proposes a novel structure of the inverted F antenna based on meandering and folding methods for the monopole antenna placed on FR4 dielectric plate. The proposed antenna has compact size (21 mm × 14 mm × 3.2 mm). Moreover, this antenna still offers enough wide bandwidth (VSWR ≤ 2), which covers 3G bandwidth. Using the simulation program to optimize antenna structure and calculate the antenna parameters in order to verify its applicability for the 3G mobile devices. © 2015 Published by VNU Journal of Science. Manuscript communication: received 04 May 2014, revised 29 April 2015, accepted 25 June 2015 Corresponding author: Ha Quoc Anh, haquocanh1812@gmail.com Keywords: 3G, Inverted F Antenna, Miniaturization of Antenna. 1. Introduction Nowadays, with the rapid growth of wireless means of communication, there is a growing demand for mobile devices that are small, thin, attractive, lightweight, and curvy. To satisfy the above demand, it is necessary to miniaturize mobile device’s components. Especially, antenna, an essential part, is miniaturized in order to put into the device. Many studies and suggestions about typical antenna structure for portable devices have been published recently. D. Bonefacic [1] proposed a design for a micro-strip antenna that works on central frequency of 2.0 GHz and has very small size (30 mm × 12.9 mm × 5 mm) but the bandwidth of the proposed antenna is too narrow (26 MHz). Y. Kim [2] proposed a folded loop antenna system for new future handsets. M. Karaboikis [3] proposed a dual- printed inverted F antenna structure for terminal devices. K. Sarabandi [4] proposed a method of miniaturized size antenna as small as 0.05λ × 0.05λ. M. Akbari [5] presented an approach to optimize the antenna structure by creating a planar inverted F antenna (PIFA). However, the overall size of the proposed antennas in the references is still quite large; therefore it is difficult for the mobile device to miniaturize its size for applications in MIMO system. In order to overcome the said shortcomings, in the reference document [6], an antenna with smaller size (23 mm × 14 mm × 5 mm) is proposed which can be applied for 3G mobile devices. In this paper, the authors use Ansoft HFSS software to miniaturize antenna structure for the 3G mobile devices based on meandering and folding methods for the monopole antenna, which is developed from the inverted F H.Q. Anh, N.Q. Dinh / VNU Journal of Science: Comp. Science & Com. Eng., Vol. 31, No. 2 (2015) 8-14 9 antenna. Next, we analyze the inverted F The input impedance of the antenna can antenna placed on a metallic plane representing a mobile device. Then, it is possible to propose a method to miniaturizing antenna structure and to design a compact antenna with dimensions of 21 mm × 15 mm × 3.2 mm, which is smaller than antennas in the reference [6]. Although its height is only 3.2 mm but its bandwidth and other technical parameters are still ensured. reach 50 Ω at the central frequency (to match perfectly with the feeder); VSWR ≤ 2; The bandwidth of the antenna is large enough: (≥ 10%, ≥ 200 MHz). 2.2. A method of miniaturizing antenna structure This antenna structure can be placed into thin Let’s consider the inverted F antenna mobile devices. In order to match the antenna input impedance with the feeder and to ensure its bandwidth must be wide enough to cover the 3G bandwidth, the antenna structure is optimized. Finally, the antenna parameters such as input impedance, VSWR, radiation pattern are calculated to validate the applicability of the proposed antenna in 3G devices. 2. The proposed antenna structure for 3G mobile devices 2.1. Main requirements of antennas for 3G mobile devices placed on a metallic plane (using copper), with dimensions of 86 mm × 40 mm × 0.1 mm, that represents a mobile device, with surveyed bandwidth from 1.8 GHz to 2.2 GHz. A FR4 dielectric plate is placed between the antenna and the metallic plane. In Fig. 1, the dimension of the FR4 dielectric plate is 40 mm × 15 mm × 3.2 mm. In order to miniaturize the size of the initial inverted F antenna, it is possible to apply meandering, folding and slotting methods [7] and apply dielectric substance FR4 to form its structure. In addition, in order to ensure the antenna input impedance, it is needed to change the current in the antenna by varying the distance between the feeding point and the grounding When design an antenna for the mobile devices, bandwidth and the requirements of point and adding U, L shape strip-lines, rectangular strip-lines. antenna compact dimensions must be taken into account. Normally, the 3G mobile devices have the length, width and thickness of 110 mm, 60 mm, and 12 mm, respectively. Currently, the 3G mobile systems in Vietnam use frequencies from 1.9 GHz to 2.17 GHz. Thus, the design antenna for 3G mobile devices has to ensure the requirements on compact size, bandwidth and several following parameters: The antenna size must be small enough to be placed in a mobile device, its height is less than 5 mm, its length and its width are less than 40 mm; Compared with the initial inverted F antenna structure, the proposed antenna has a U-shape strip-line with the parameter of s and two rectangular strip-lines with the parameters of l1 × l2 and l6 × l7, as shown Fig. 2. Adding these strip-lines will change the current distribution on the antenna. This in turn will change the antenna input impedance and therefore help the impedance matching with the feeder. Moreover, the optimized antenna will expand the bandwidth and ensure more compact size. 10 H.Q. Anh, N.Q. Dinh / VNU Journal of Science: Comp. Science & Com. Eng., Vol. 31, No. 2 (2015) 8-14 mm (length), 14 mm (width), and 3.2 mm (height). A gap between the feeding point and the grounding point is l5 = 9 mm. Except for the Antenna strip-lines are connected to the metallic plane, other strip-lines are fixed on the dielectric FR4 plate and parallel to the ground. L To choose the optimal parameters of Ground plane W antenna as shown in Table I, we examine of the effect of antenna size parameters to VSWR. 2.3. Impact of VSWR when changing antenna size parameters 2.3.1. Impact of VSWR when changing l3 Fig. 1. The antenna structure. 2.0 3G bandwidth (270 MHz) After many experiments, an optimized antenna structure is chosen. The size of the optimized antenna elements is shown in Table I. 1.5 3 3 1 2 8 7 1 1.0 1.80 1.85 l3 = 14.5 mm l3 = 14.0 mm l3 = 13.5 mm 1.90 1.95 2.00 2.05 2.10 2.15 2.20 Frequency [GHz] s 6 z h 5 x Fig. 3. The effect of l3 to VSWR. 4 2 The results of calculating the dependence of parameter l3 on the VSWR is represented in Fig. 3. For VSWR ≤ 2, when increasing the y Feedingpoint Groundingpoint length l3, the electrical length of monopole antenna increases so that resonance frequency and bandwidth of antenna decrease. In Fig. 2. The structure of proposed antenna. contrast, when reducing the length l3, the Antenna is connected with the metallic plane by 2 points, the feeding point and the grounding point. This antenna structure consists of copper strip-lines of width w2 = 1 mm, thickness is 0.1 mm. The overall dimensions of the antenna are chosen with 21 bandwidth of antenna increases but it does not cover the bandwidth of 3G mobile devices. As a result, in order to have bandwidth of antenna cover the working bandwidth of 3G mobile devices, it is necessary to select parameter l3 = 14.0 mm. H.Q. Anh, N.Q. Dinh / VNU Journal of Science: Comp. Science & Com. Eng., Vol. 31, No. 2 (2015) 8-14 11 2.3.2. Impact of VSWR when changing l5 In Fig. 5, similar to the parameter l3, when 2.0 1.5 3G bandwidth (270 MHz) increasing the length l6, the electrical length of monopole antenna increases, therefore resonance frequency and bandwidth of antenna decrease. In contrast, when reducing the length l6, the bandwidth of antenna increases but it does not cover the bandwidth of 3G mobile l5 = 8.5 mm l5 = 8.0 mm l5 = 7.5 mm 1.0 1.80 1.85 1.90 1.95 2.00 2.05 2.10 2.15 2.20 devices (with VSWR ≤ 2). Therefore, parameter l6 must be selected with optimal value is 11.0 mm. 2.3.4. Impact of VSWR when changing l8 Frequency [GHz] Fig. 4. The effect of l5 to VSWR. The results of calculating the dependence of parameter l5 on the VSWR is represented in Fig. 4. For VSWR ≤ 2, when increasing the length l5, the distance between the feeding point and the grounding point increases, therefore current in the antenna changes. This makes resonance frequency and bandwidth of antenna increase. In contrast, when reducing the length l5, the bandwidth of antenna decreases. However, in both cases, bandwidth of antenna does not cover the bandwidth of 3G mobile 2.0 1.5 1.0 1.80 1.85 3G bandwidth (270 MHz) l8 = 3.2 mm l8 = 2.8 mm l8 = 2.4 mm 1.90 1.95 2.00 2.05 2.10 2.15 2.20 Frequency [GHz] devices. Therefore, parameter l5 must be selected with optimal value is 8.0 mm. 2.3.3. Impact of VSWR when changing l6 Fig. 6. The effect of l8 to VSWR. The results of calculating the dependence of 2.0 1.5 l6 = 11.5 mm 3G bandwidth (270 MHz) parameter l8 on the VSWR is represented in Fig. 6. Similar to other parameters, when changing the length of l8 compared with the optimal value, the bandwidth of antenna (with VSWR ≤ 2) does not cover the bandwidth of 3G mobile devices. Therefore, parameter l8 must be selected with optimal value is 2.8 mm. l6 = 11.0 mm l6 = 10.5 mm 1.0 1.80 1.85 1.90 1.95 2.00 2.05 2.10 2.15 2.20 Frequency [GHz] Fig. 5. The effect of l6 to VSWR. Similarly, when analyzing the effects of changing other parameters to VSWR, the optimal dimensions of the antenna are chosen, as shown in Table I. 12 H.Q. Anh, N.Q. Dinh / VNU Journal of Science: Comp. Science & Com. Eng., Vol. 31, No. 2 (2015) 8-14 Table I. The size of the proposed antenna (MM) Parameters Value L 80 W 40 h 3.2 s 1 w1 15 Parameters w2 w3 l1 l2 l3 TAJ Value Parameters Value 1 l4 7 21 l5 8 6 l6 11 7 l7 6.5 14 l8 2.8 2.4. Simulated results of the proposed antenna 50j Simulated results in the input impedance and VSWR of the optimized antenna are shown in Fig. 7 and Fig. 8, respectively. The radiation 25j 100j pattern in the xz and yz planes for the frequencies of 1.90 GHz, 2.02 GHz and 2.17 GHz are plotted 10j -10j 250j 10 25 50 100 250 2.02 GHz (40 Ω) -250j -25j -100j in Fig. 9. 0 330 4 0 300 -4 -8 -12 270 -16 -12 30 yz plane xz plane 60 90 -50j Fig. 7. Input impedance of the proposed antenna. 285 MHz 2.0

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