Here a compact wideband diversity antenna covering the PCS/UMTS/WiMAX bands with high isolation and low enveloped correlation coefficient (ECC) is proposed. To widen the bandwidth, the proposed antenna uses a structure with a gap-coupled feed and an inductively shorted line that has capacitive compensation between the radiator and the ground plane. Also, a suspended line with a parasitic element is used to enhance the isolation between the two antennas

Bunggil Yu

Byeongkwan Kim

Byungje Lee

Chang Won Jung

Deokyun Kim

Haechun Lee

Hyunho Wi

Myun-Joo Park

Yonggyu Choi

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International Journal of Antennas and Propagation
Volume 2012, Article ID 798046, 6 pages
doi:10.1155/2012/798046
Research Article
Closely Mounted Compact Wideband Diversity Antenna for
Mobile Phone Applications
Bunggil Yu,1 Chang Won Jung,2 Haechun Lee,3 Myun-Joo Park,4 Byeongkwan Kim,4
Hyunho Wi,4 Yonggyu Choi,4 Deokyun Kim,4 and Byungje Lee4
1 Communication R&D Center, Samsung Thales Co., Seongnam-Si, Gyeonggi-Do, 463-870, Republic of Korea
2 Graduate School of NID Fusion Technology, Seoul National University of Technology, 172 Gongneung-2 Dong, Nowon-Gu,
Seoul 139-743, Republic of Korea
3 Department of Electric Energy System, Korea Polytechnic College II, 448-56, Munemiro, Gusan-Dong, Bupyeong-Gu,
Incheon 403-719, Republic of Korea
4 Department of Wireless Communications Engineering, Kwangwoon University, 447-1 Wolgye-Dong, Nowon-Gu,
Seoul 139-701, Republic of Korea
Correspondence should be addressed to Byungje Lee, bj lee@kw.ac.kr
Received 6 January 2012; Accepted 13 March 2012
Academic Editor: Seong-Youp Suh
Copyright © 2012 Bunggil Yu et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Here a compact wideband diversity antenna covering the PCS/UMTS/WiMAX bands with high isolation and low enveloped
correlation coefficient (ECC) is proposed. To widen the bandwidth, the proposed antenna uses a structure with a gap-coupled feed
and an inductively shorted line that has capacitive compensation between the radiator and the ground plane. Also, a suspended
line with a parasitic element is used to enhance the isolation between the two antennas.
1. Introduction
The implementation of antenna diversity is a well-known
technique for enhancing the performance of wireless com-
munication systems since it reduces multipath fading and
cochannel interference [1]. However, mutual coupling bet-
ween antennas degrades their performance. Consequently,
various methods have been studied to enhance isolation
between antennas within the limited space of mobile phones,
including the protruded T-shape ground [2, 3], the quarter
wavelength slot on the ground [4, 5], and the jointed shorting
and suspended line [6–8]. These methods can effectively
reduce the mutual coupling between antennas, but they oc-
cupy large spaces and provide narrow bandwidth. The diver-
sity antenna of a mobile phone requires low profile and low
cost while maintaining a wide bandwidth, good isolation,
and a low correlation coefficient. The correlation coefficient,
which is closely related to interantenna isolation, is the most
important factor to be considered in the design of a diversity
antenna.
In this paper, a compact wideband diversity antenna with
an impedance bandwidth of 45% is proposed. This design
is accomplished through use of a capacitive gap-coupled
feed and an inductive shorted line. To improve the isolation
between two antennas, a suspended line with a parasitic
element is employed. The isolation of the proposed antenna
is higher than 18 dB within 1.75–2.66 GHz. With this
high isolation and the orthogonal radiation pattern, a low
enveloped correlation coefficient (ECC) can be also achieved
from the far-field pattern calculation [9].
2. Antenna Configuration and Design
Figures 1 and 2 show the geometry and a photograph of
the proposed antennas, respectively. The size of the ground
plane is 45 × 85 × 1 mm3 and the size of the diversity
antenna is 45 × 15 × 1 mm3. The proposed antennas are
printed on top and bottom layers of FR4 (εr = 4.4) substrate,
and the detailed dimensions are shown in Figures 1(b)
and 1(c). The proposed antennas consist of a gap-coupled
2 International Journal of Antennas and Propagation
Layer 2
(bottom)
Ground plane
45 mm × 85 mm
Port 2
Parasitic element
Port 1 Layer 1
(top)
Antenna 2
Feed line 2
Feed line 1
Antenna 1
z
y
x
Via
Via
FR4
Suspended line
(a)
45
2
8
161
15
7
Port 2Port 1
Ground plane
z
x
y
Unit: (mm)
(b)
x
10.5
11.25
1
10.5 10.5
0.51
L = 20
Ground plane
z
y
1
1
Unit: (mm)
(c)
Figure 1: Geometry of the proposed antenna: (a) overall view, (b) detailed view of layer 1 (top), and (c) detailed view of layer 2 (bottom).
x
z
y
x
z
y
Figure 2: Photograph of the fabricated antenna.
International Journal of Antennas and Propagation 3
1.6 1.8 2 2.2 2.4 2.6 2.8 3
−40
−30
−20
−10
Frequency (GHz)
Without suspended line
and parasitic element
With suspended line
and parasitic element
PCS/UMTS WiMAX
0
|S 2
1
|(
dB
)
With suspended line
only
Figure 3: Simulated isolations (S21).
1.6 1.8 2 2.2 2.4 2.6 2.8 3
−40
−30
−20
−10
Frequency (GHz)
Without suspended line
and parasitic element
With suspended line only
With suspended line
and parasitic element
PCS/UMTS WiMAX
0
|S 2
1
|(
dB
)
Figure 4: Measured isolations (S21).
|S-
pa
ra
m
et
er
s|
(d
B
)
S11
S21
1.6 1.8 2 2.2 2.4 2.6 2.8 3
−40
−30
−20
−10
Frequency (GHz)
PCS/UMTS WiMAX
0
−6 dB
Figure 5: Measured S-parameters of the proposed antenna.
4 International Journal of Antennas and Propagation
0 30
60
120
150
180
210
240
270
300
330
Antenna 1
Antenna 2
−40
−30
−20
−10
0 [+z]
90 [+y]
(a)
30
60
120
150
180
210
240
270
300
330
Antenna 1
Antenna 2
0
−40
−30
−20
−10
0 [+z]
90 [+y
(b)
30
60
120
150
180
210
240
270
300
330
Antenna 1
Antenna 2
0
−40
−30
−20
−10
0 [+z]
90 [+y]
(c)
30
60
120
150
180
210
240
270
300
330
PCS band
UMTS band
WiMAX band
0
−40
−30
−20
−10
0 [+x]
90 [+y]
(d)
Figure 6: Measured radiation patterns: (a) yz-plane, PCS band, (b) yz-plane, UMTS band, (c) yz-plane, WiMAX band, and (d) xy-plane,
PCS/UMTS/WiMAX bands when Antenna 1 is excited.
feed, an inductive shorted line, and a suspended line with
a parasitic element. The gap-coupled feed and the radiator
are printed on the top layer. The inductive shorted line and
the suspended line with the parasitic element are printed on
the bottom layer. The top and bottom layers are electrically
connected via holes. To widen the bandwidth, we propose
use of the inductively shorted line-connected monopole with
a gap-coupled feed. The main function of the proposed
inductively shorted line and the gap-coupled monopole is
to provide triple resonance modes in a monopole. The first
resonance mode originates from the quarter wavelength
monopole. The second and third resonant modes are due
to input impedance enhancement by the inductively shorted
line and the gap-coupled feed. They provided capacitive
compensation between the radiator and the ground plane to
improve the input impedance matching of the second and
third resonant frequencies. Finally, the frequencies of the
triple resonances are close together and, hence, the proposed
antennas achieve wide bandwidth. The suspended line
positioned at the inductive shorted lines also enhances the
isolation between two antennas. The suspended line actually
acts as a neutralization device by picking up a certain amount
of the signal on one antenna and feeding it back to the
other. A particular combination of length and width of the
suspended line can lead to a better isolation level. In addition,
the parasitic element maximizes the antenna isolation. The
proposed parasitic element operates as the open stub (λ/4),
so that this parasitic element can suppress the surface
current on the ground plane between the closely located two
antennas.
3. Result and Discussion
Figures 3 and 4 show the simulated and measured isolations
(S21) between two antennas without both the suspended
line and the parasitic element, with the suspended line only,
and with both the suspended line and the parasitic element.
It demonstrates that a high isolation (>18 dB), which is
generally accepted for practical applications in industries,
can be achieved for all frequency bands, especially for the
PCS and UMTS band, through adding the parasitic element
on the suspended line. The measured reflection coefficients
(S11) and isolation (S21) of the proposed antenna are shown
in Figure 5. The proposed antenna can cover the PCS (1.85–
1.99 GHz)/UMTS (1.92–2.17 GHz)/WiMAX (2.5–2.6 GHz)
bands (VSWR 3 : 1) with a compact size and wide bandwidth.
Figure 6 shows that polarizations of the diversity Antennas 1
and 2 are orthogonal to each other. They have been measured
International Journal of Antennas and Propagation 5
1.6
0
0.1
0.2
0.3
0.4
0.5
0.6
Simulation
Measurement
PCS/UMTS WiMAX
E
nv
el
op
ed
 c
or
re
la
ti
on
 c
oe
ffi
ci
en
t
(E
C
C
)
1.8 2 2.2 2.4 2.6 2.8 3
Frequency (GHz)
Figure 7: Simulated and measured ECC.
PCS/UMTS WiMAX
1.6 1.8 2 2.2 2.4 2.6 2.8
0
10
20
30
40
50
60
70
80
90
Frequency (GHz)
A
n
te
n
n
a 
effi
ci
en
cy
 (
%
)
Figure 8: Measured efficiency of the proposed antenna.
with one antenna excited and the other terminated to a load
with 50Ω. In general, two antennas are orthogonally located
to each other so that they can provide the polarization
diversity and then reduce the mutual coupling between
them. In this paper, a compact antenna for the polarization
diversity is achieved by arranging two PIFAs linearly along
the y-axis. The E-field directions of the proposed diversity
antennas for PCS (Figure 6(a)), UMTS (Figure 6(b)), and
WiMAX (Figure 6(c)) bands are diagonally orthogonal to
each other even though two antennas are linearly (front-
to-front) mounted with the suspended line and the par-
asitic element. Since these two symmetrical PIFAs have
both vertical (due to current on the radiating element)
and horizontal (due to current on the ground plane) E-
field components, their E-field directions are diagonal and
orthogonal to each other as shown in Figures 6(a), 6(b),
and 6(c). Therefore, these orthogonal radiation patterns,
and high isolation (>18 dB) give a very low ECC (<0.2) of
the proposed antenna as shown in Figure 7. The proposed
antenna has also a high efficiency of >67% as shown in
Figure 8 for all operating frequency bands.
4. Conclusion
A compact wideband diversity antenna is proposed for
mobile phone applications. It has a very low profile, high
radiation efficiency (>67%), high isolation (>18 dB), and low
ECC (< 0.2). The measurement results confirmed that the
proposed antenna has a wide bandwidth through use of a
gap-coupled feed and an inductively shorted line and that
it also has good isolation performance through the use of
a suspended line with a parasitic element. The operation
frequency band (VSWR 3 : 1) of the proposed antenna
is 1.78–2.8 GHz (1.02 GHz; 45%) and includes a required
6 International Journal of Antennas and Propagation
triple service band of PCS (1.85–1.99 GHz), UMTS (1.92–
2.17 GHz), and WiMAX (2.5–2.6 GHz).
Acknowledgment
The present research has been conducted by the Research
Grant of Kwangwoon University in 2012.
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Closely Mounted Compact Wideband Diversity Antenna for Mobile Phone Applications

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Closely Mounted Compact Wideband Diversity Antenna for Mobile Phone Applications

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