Received: 10 April 2017

| Revised: 26 June 2017

| Accepted: 27 June 2017
DOI: 10.1002/mmce.21143

RESEARCH ARTICLE

A frequency reconfigurable antenna for multiband mobile handset

applications

Xiaoyan Zhang1,2 | Miao Tian1 | Aiyun Zhan1 | Zhiwei Liu1 | Haiwen Liu1

1
School of Information Engineering, East
Abstract
China Jiaotong University, Nanchang,
China A frequency-reconfigurable antenna is presented for multiband (GSM850/900/GLO-
2
State Key Laboratory of Millimeter NASS1616/DCS1800/PCS 1900/UMTS/LTE2300/2500/WLAN) mobile handset
Waves, Nanjing, China applications. It mainly consists of radiating elements with two PIN diodes. By
switching the ON/OFF states of the PIN diodes, the proposed structure can operate in
Correspondence three states: OFF–ON, ON–OFF, and ON–ON. When PIN diodes are in the OFF–
Xiaoyan Zhang, School of Information ON states, the proposed antenna can cover the GSM850/900, PCS1900, and
Engineering, East China Jiaotong
UMTS2100 bands by operating in Invented-F antenna (IFA) mode. When PIN
University, Nanchang, China.
Email: xy_zhang3129@ecjtu.jx.cn diodes are in the ON–OFF states, the antenna can cover the LTE2300/2500 and
WLAN2400 bands in monopole mode. Moreover, when PIN diodes are switched to
Funding information the ON–ON states, the designed antenna works in loop mode and its resonant fre-
Open Project of State Key Laboratory of quencies include the GLONASS1616, DCS1800/1900, and LTE2500 bands. With
Millimeter Wave through, Grant/Award the reconfigurable technique, the proposed antenna achieves a compact size of 15 3
Number: #K201829; National Natural
28.5 mm2 with high efficiency from 34% to 84.86% in the total frequency range.
Science Foundation of China, Grant/Award
Number: #81460275; Jiangxi Provincial
Department of Education Fund, Grant/ KEYWORDS
Award Number: #GJJ160504; Jiangxi frequency PIN diode, mobile handset antenna, multiband, reconfigurable antenna
Natural Science Foundation, Grant/Award
Number: #20161BAB202062

1 | INTRODUCTION In refs 1–4, some multiband printed monopole antennas

with 3-D structures were developed. However, these designs
The rapid development of mobile and portable communica- are no longer suitable for the recent portable devices due to
tion systems has led to an increased interest in more com- their sizable obstacles in a very small space.
pact internal antennas designs. These antennas are required Although 3-D antennas can be further compressed to be
to be small enough to be built in a practical mobile hand- 2-D structures by coupled-feed techniques,5,6 they still
set. Meanwhile, they must have good performance in terms occupy a very large clearance zone. To reduce the size of the
of impedance bandwidth, radiation pattern, and efficiency. antennas and still ensure they can cover a wide operating
However, due to the limited space, antenna design is often band, the frequency-reconfigurable technology based on dif-
problematic to include all various frequency bands, such as ferent tuning methods is studied,7,9–15 which has been vali-
global system for mobile communications (GSM), the dated to be one of the most effective ways in minimizing
global positioning system (GPS), the digital cellular system antenna designs. Instead of adding the extra structures, the
(DCS), the personal communication system (PCS), the uni- antennas mainly control the electrical length of the current
versal mobile telecommunication system (UMTS), and the path by independently adjusting the states of the switches
wireless local area network (WLAN) with high efficiency located in the radiating elements in real time. With this
when several electronic devices or components are inte- approach, these antennas can operate at different frequencies.
grated on the same small terminals. The increased integra- Then, by combining these states, the diverse service bands
tion density is driving the antenna design toward multiband can be merged. Consequently, the bandwidth can be
operation. expanded by multiple times.

Int J RF Microw Comput Aided Eng. 2017;e21143. wileyonlinelibrary.com/journal/mmce V

C 2017 Wiley Periodicals, Inc. | 1 of 8
https://doi.org/10.1002/mmce.21143
2 of 8 | ZHANG ET AL.

T A BL E 1 Frequency bands and size of previously reported antennas and the proposed antenna

Reference no. Frequency bands Total number of frequency bands Size/mm3

12 GSM850/900/DCS1800/ 7 73 70 3 0.8
PCS1900/UMTS2100/
LTE2300/2500

13 GSM850/900/DCS1800/ 7 55 3 533
PCS1900/UMTS2100/
LTE2300/2500

14 GSM850/900/PCS1800/ 8 (30 3 15–5 3 15 ) 3 0.8

1900/UMTS2100/
LTE2300/2500/GNSS

15 GSM850/900/DCS1800/ 8 75 3 103 5
PCS1900/UMTS2100/
LTE2300/2500/WLAN

Proposed antenna GSM850/900/DCS1800/ 9 28.5 3 15 3 0.8

PCS1900/UMTS2100/
LTE2300/2500/WLAN/
GLONASS1616

Various switching technologies such as radiofrequency controlling the state of the PIN diodes. The proposed struc-
micro-electro-mechanical systems (RF-MEMS) switches,7 ture operates in three modes and can cover the GSM850
variable capacitance switches,7,8 varactor diodes,9,10 and PIN (824–894 MHz), GSM900 (880–960 MHz), GLONASS1616
diodes11–15 are used to design the frequency-reconfigurable (1610–1626.5 MHz), DCS1800 (1710–1880 MHz),
antennas. Among them, the PIN diodes are particularly well PCS1900 (1850–1990 MHz), UMTS2100 (1920–
suited for integration in current portable electronic devices 2170 MHz), LTE2300 (2300–2400 MHz), WLAN (2400–
owing to its simple design, small size, and economic cost. 2480 MHz), and LTE2500 (2500–2690 MHz) bands. To
In this article, a reconfigurable printed antenna with pla- compare our proposed antenna with antennas reported in refs
nar structure is proposed for mobile handset applications by 12–15, which were published in recent years, the operating
bands and the sizes of the antennas are summarized in Table
1. It shows that the proposed antenna covers more frequency
bands and has a compact size.
This article is arranged in the following manner. In Sec-
tion 2, the configuration of the proposed antenna is described
in detail. In Section 3, the working principle of the antenna
is analyzed. In Section 4, the measured results of the

T A BL E 2 Configurations of the proposed antenna depending on

bias states of two PIN diodes

Bias state of two PIN diodes

Represented states #1 #2 Configuration

Antenna 1 (OFF–ON) OFF ON

Antenna 2 (ON–OFF) ON OFF

Antenna 3 (ON–ON) ON ON

FIGURE 1 Geometry of the proposed antenna: (A) overall structure

and (B) main radiator
ZHANG ET AL.
| 3 of 8

substrate with a permittivity of 4.4, a loss tangent of 0.02,

and a thickness of 0.8 mm. The size of the structure is 15 3
28.5 mm2 (Figure 1B). A ground plane with a size of 100 3
15 mm2 and 15 3 17 mm2 is printed on the bottom layer of
the substrate, which has been subtracted a projection of the
antenna to construct a 15 3 33 mm2 clean zone. The whole
circuit is enclosed by a 50 3 1 3 10 mm3 plastic housing
with a relative permittivity of 3.3, a loss tangent of 0.02,
which is used to simulate the shell of a mobile device. The
detailed structure and optimized dimensions are shown in
Figure 1B.
As Figure 1B shows, the designed antenna mainly con-
sists of radiating elements, that is, a longer strip (C-E-V-F-
G-H-I-J-K), a shorter strip (B-K-D), and a feed line (A-C).
The widths of the feed-line and the short strip are fixed to 1
and 2 mm respectively, which corresponds to 50 X in the
used substrate. The distance between them is 9 mm. Except
for the strip (B-K-D), the widths of the other strips are the
same as that of the feed-line. Two capacitors, that is, C1 and
C2, are embedded into the strips between points V and F and
between points A and C, respectively. And two PIN diodes
(BAR64–02) are located on radiating element: PIN diode #1
is placed between points J and K and PIN diode #2 is
between points E and V. When PIN diodes are turned on,
the gaps can be bridged. In addition, by adjusting the ON/
OFF states of the diodes, different configurations of the
antenna could be switched.
Table 2 shows the specific structures of the proposed
antenna depending on the various bias states of two PIN
diodes. From Table 2, we can see, when PIN diode #1 is
turned off (in OFF state) and PIN diode #2 is turned on (in
ON state), the diodes’ states are represented as “OFF–ON”
and the radiating elements of the antenna are composed by a
longer strip (C-E-V-F-G-H-I-J) and a shorter strip (B-K-D).
While, when PIN diode #1 is turned on but the PIN diode #2
is turned off, we call them in “ON–OFF” states. In this case,

F I G U R E 2 Simulated reflection coefficients of the antennas with

loaded capacitors or not

constructed prototype are presented. In Section 4, a conclu-

sion is made.

2 | ANTENNA DESIGN AND

PARAMETRIC STUDIES

2.1 | Antenna configuration

Figure 1A,B shows the geometry of the proposed antenna. FIGURE 3 Simulated reflection coefficients of antenna 1 with vari-
The antenna is fabricated on the top layer of a FR-4 dielectric ous C1
4 of 8 | ZHANG ET AL.

capacitors of C1 and C2. The numerical results are also com-

pared with the original antenna without any capacitors. A
return loss of 6 dB is used as a standard, which is satisfied
with the desired service bands.
As Figure 2A shows, if only C1 is added into the radia-
tion elements of antenna 1 (PIN diodes in OFF–ON states),
the low-resonance frequency will shift, but the high frequen-
cies almost keep the same. However, this phenomenon does
not occur in antenna 2 (PIN diodes in ON–OFF states) and
antenna 3 (PIN diodes in ON–ON states), as their low-
resonance frequency are still high (Figure 2B,C), which
means C1 just has a great effect on low frequencies. In short,
no matter what the switches are, all the figures show that
adding both C1 and C2 into the proposed antenna will cause
a wider bandwidth and a better impedance match.
To analyze such effect, the antenna in OFF–ON state is
illustrated. Different values of 3.1, 5.1, and 6.1 pF are set to
C1. Figure 3 gives their S11 results comparisons. It can be
seen that the return loss will increase with C1 decrease.
Therefore, the low-resonance frequencies can be adjusted by
changing C1. However, their bandwidths are still too narrow
to cover GSM850 and GSM900 bands. Thus, C2 is intro-
duced to help the antenna design. C2 is loaded into the feed-
line as a series capacitor, so the reactance introduced by C2
is 1/jxC2, where x is an angular frequency. Apparently, the
reactance of the feed-line would be increased as C2 decrease.
Different values of 2, 2.2, and 2.5 pF are set to C2. Fig-
ure 4 illustrates the comparisons of the simulated S11 results

FIGURE 4 Simulated reflection coefficients of the antennas by load-

ing different C2

the radiating elements become a longer strip (V-F-G-H-I-J-

K) and a shorter strip (A-C-W-E).

2.2 | The effects of capacitors on antenna

performance
For impedance matching, two capacitors C1 and C2 are
induced. Figure 2 gives the comparisons of S11 results of the FIGURE 5 Surface electric current distributions of antenna 1 at two
antennas (Table 2) with loading single capacitor of C1 or two resonant frequencies: (A) 900 MHz and (B) 2100 MHz
 ZHANG ET AL.
| 5 of 8

T A BL E 3 Operating modes and bands of the proposed antenna

Configuration Operating band Operating mode

Antenna 1 GSM850/900, IFA

PCS1900/UMTS2100

Antenna 2 LTE2300, Monopole

WLAN2400, LTE2500

Antenna 3 GLONASS1616, Loop

DCS1800, LTE2500

F I G U R E 6 Surface electric current distributions of antenna 2 at reso-

nance frequency of 2300 MHz resonance frequencies, and the resonance frequency cover
GSM850/900 and PCS1900/UMTS2100 bands. As Figure
of the antenna in three states. As Figure 4 shows, the middle 5A shows, at 900 MHz, the electric current flows from the
frequencies of the antenna will increase with C2 increase. longer strip (J-I-H-F-E-W-C-A) into the feeding line. The
Obviously, the introduction of C2 significantly changes the length of the electric current is about 80.5 mm, which
antenna’s performance. When C2 5 2.2 pF, the impedance approximately equals 1/4 of the resonance wavelength. In
marching at the low-resonance frequencies are the best. Figure 5B, the electric current flows along two different
pathways. One flows through F-E-W-C-A and the other
along the path of F-G-H-I-J. The total length of the electric
3 | WORKING PRINCIPLE OF THE current is 2 3 1/4k, where k is the resonance wavelength of
PROPOSED ANTENNA 2100 MHz. In both cases, the proposed antenna works as
IFA mode.
To understand how the proposed antenna works, the surface Figure 6 shows the surface current distributions of
electric current distributions at resonance frequencies are antenna 2, which has only one resonant frequency of 2300
F5-F7 shown in Figures 5–7. MHz, and 26 dB coverage of the band includes LTE2300/
Figure 5 demonstrates the surface electric current distri- 2500 and WLAN2400. The antenna works as monopole
butions of antenna 1. At this time, the antenna produces two mode. And the electric current flows from point E to point A
with a 23.5 mm length, which is about one-fifth of the reso-
nant wavelength.

F I G U R E 8 Photographs of the fabricated antenna: (A) the diagram

FIGURE 7 Surface electric current distributions of antenna 3 at two of the proposed antenna with driving circuit and (B) driving circuit of PIN
resonant frequencies: (A) 1800 MHz and (B) 2570 MHz diodes
6 of 8 | ZHANG ET AL.

FIGURE 9 Measured S11 of the proposed antenna

The surface electric current of antenna 3 is shown in Fig-

ure 7. In this case, the proposed antenna has dual resonances
in the high band. As shown in Figure 7A, at 1800 MHz, the
antenna also operates in loop mode. The surface current
flows through two pathways: F-E-C-A and F-G-H-I-J-K-B.
Each current path has a 1/4k length. In Figure 7B, the sur-
face current flows into the feeding line. Meanwhile, it also
flows from the short strip to the long strip as well. The cur-
rent path is 3 3 1/4k length. This proves that the resonant
mode operates as loop mode.
The operating modes and the operating bands of the pro-
posed antenna for bias states of two PIN diodes are summar-
ized in Table 3.

4 | MEASURED RESULTS

To test the performance of our design, a simple driving cir-

cuit is used to control the bias states of the PIN diodes. Fig-
ure 8A,B shows the photographs of the fabricated antenna.
The diagram of the driving circuit is shown in Figure 8C. A
two-pin DIP switch with a 3 V battery source is used to

F I G U R E 1 1 Measured radiation patterns of proposed antenna at res-

onant frequencies: (A) 900 MHz, (B) 1900 MHz, (C) 2100 MHz, (D)
2400 MHz, and (E) 2570 MHz

control the bias states of the PIN diodes. Two 500 X resistors
and four 470 nH inductors are utilized to control the bias
current.
Figure 9 shows the measured S11 of the proposed
antenna. The measured results show that when the diodes in
FIGURE 10 Measured results of the proposed antenna: peak gain OFF–ON states, the 26 dB impedance bandwidth of the pro-
and efficiency posed antenna is 24.2% (820–1030 MHz) at the lower band,
ZHANG ET AL.
| 7 of 8

which covers GSM850/900 bands, and 25.9% (1900–2470 through Grant #K201829, National Natural Science Foun-
MHz) at the upper band, which covers UMTS2100/PCS1900 dation of China through Grant #81460275, Jiangxi Provin-
bands. Then, for the diodes in ON–OFF states, 30.1% band- cial Department of Education Fund #GJJ160504, Jiangxi
width of 2090–2810 MHz is obtained. This antenna can be Natural Science Foundation through Grant
employed for LTE2300/2500 bands and WLAN2400 band. #20161BAB202062, all of them from China.
While, when the two PIN diodes are turned on, 20.8%
(1600–2090 MHz) and 5.8% (2640–2800 MHz) bandwidths R EFE RE NC ES
are achieved, which can cover the GLONASS1610/
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[14] Xu Y, Liang YW, Zhou HM. Small-size reconfigurable antenna

HAIWEN LIU (M’04-SM’13) received the
for WWAN/LTE/GNSS smartphone applications. IET Micro-
wave Antennas Propag. 2017;11:923–928.
BS degree in electronic system and MS
degree in radio physics from Wuhan
[15] Xu H, Wang H, Gao S, et al. A compact and low profile loop
antenna with six resonant modes for LTE smartphone. IEEE University, Wuhan, China, in 1997 and
Trans Antennas Propag. 2016;64:3743–3751. 2000, respectively, and the PhD degree
in microwave engineering from Shang-
hai Jiao Tong University, Shanghai,
A U T HO R B IO G R A P H I E S China, in 2004. From 2004 to 2006, he was with Waseda
XIANYAN ZHANG received the BS degree University, Kitakyushu, Japan, as a Research Assistant Pro-
in applied physics and MS degree in fessor. From 2006 to 2007, he was a Research Fellow with
physical electronics from Yunnan Uni- Kiel University, Kiel, Germany, where he was granted the
versity, Kunming, China, in 2001 and Alexandervon Humboldt Research Fellowship. From 2007 to
2004, respectively, and the PhD degree 2008, he was a Professor with the Institute of Optics and
in Electromagnetic Field and Microwave Electronics, Chengdu, China, where he was supported by the
Technology from Institute of Electronics, 100 Talents Program of Chinese Academy of Sciences. Since
Chinese Academy of Sciences in 2007. Her research interests 2009, he has been a Chair Professor with East China Jiaotong
include electromagnetic computation, antenna design, and University, Nanchang, China. He has published more than
wireless power transmission structure design. 100 papers in international and domestic journals and confer-
ences. His current research interests include electromagnetic
MIAO TIAN received the BS degree in
modeling of high-temperature superconducting circuits, radio
communication engineering from North-
frequency, and microwave passive circuits and systems, syn-
western Polytechnical University Ming
thesis theory and practices of microwave filters and devices,
De College, Xi’an, China. She is cur-
antennas for wireless terminals, and radar system. He was a
rently studying at School of Information
recipient of Wang Kuancheng Science Foundation in 2008;
Engineering, East China Jiaotong Uni-
the Best Paper Prize of the 2005 International Conference on
versity. Her research interests focus on
Communications, Circuits and Systems Proceedings in Hong
antenna design.
Kong; the Prize of Osaka City Mayor for Conference of Chi-
AIYUN ZHAN was born in Nantong, nese Alumni in Japan in 2005; the 100 Best PhD Disserta-
Jiangsu, China in 1973. She received BS tions in Shanghai, China, in 2006; the National Distinguished
degree from Southwest Jiaotong Univer- PhD Student Scholarship, China, in 2003; the National First-
sity in 1997 and MS degree in East Class Guanghua Education Scholarship, China, in 2002; and
China Jiaotong University in 2008. She the Huawei Company Scholarship, China, in 1999. Dr Liu
is currently working at School of Infor- has served as a Technical Program Committee Member for
mation Engineering, East China Jiaotong many international conferences and a reviewer for some inter-
University. Her research interests focus on channel coding national journals, including the IEEE Transactions on Micro-
and optical communication. wave Theory and Technique, IEEE Transactions on Applied
ZHIWEI LIU was born in Nanchang, Superconductivity, IEEE Transactions on Industrial Electron-
Jiangxi, China in 1982. He received BS ics, IEEE Transactions on Components, Packaging and Man-
degree in computer science from Nanjing ufacturing Technology, IEEE Microwave and Wireless
University of Science and Technology in Components Letters, and IEEE Antennas and Wireless Prop-
2003, MS degree in Nanjing Institute of agation Letters.
Electronics and Technology in 2006, and
PhD degree in Nanjing University of
Science and Technology in 2011, respectively. He was with How to cite this article: Zhang X, Tian M, Zhan A,
the Department of Electrical and Computer Engineering, Liu Z, Liu H. A frequency reconfigurable antenna for
Iowa State University, as a visiting scholar in 2009. He is cur- multiband mobile handset applications. Int J RF
rently working at School of Information Engineering, East Microw Comput Aided Eng. 2017;e21143. https://doi.
China Jiaotong University. His research interests focus on the org/10.1002/mmce.21143
theory of electromagnetic scattering and inverse scattering.