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Design of GSM/LTE multiband applicationfor mobile phone antennas

Yu-Jen Chou, Guo-Sheng Lin, Jun-Fu Chen, Lih-Shan Chenand Mau-Phon Houng

A novel compact multiband planar antenna fed by a microstrip line

structure is presented. The proposed antenna is developed for wireless

communication applications of the global system for mobile (GSM)

communication and long-term evolution (LTE) in different service

bands of 900, 1800, 1900, 2300, and 2500 MHz. The antenna has

ve bands, and the structure is a combination of a monopole antenna

and a coupled ground line fabricated on an FR4 substrate. The pro-

posed antenna can be embedded in mobile phones for GSM and

LTE applications. The measured peak gains are 2.12 and 3.82 dBi

for the GSM and LTE bands, respectively.

Introduction: The multiband was designed on a single antenna to meet

the needs of multifunctional wireless communication systems. Since the

introduction of compact mobile devices, designing an internal compact

multiband antenna has become a challenging topic. For general handset

applications, several compact and wideband techniques are employed to

achieve compact multiband antenna operating bands. In [1, 2],

multi-loop-type antennas with a meander structure were utilised to

attain multiband and a compact size. In [3], bendable planar

inverted-F antennas were utilised to achieve compact size. Other multi-

band techniques include using a multi-branch antenna structure [4], uti-

lising a slot antenna structure [5], and loading a parallel resonant

structure in antennas [6].

In this Letter, we propose a multiband antenna solution for the global

system for mobile (GSM) communication and long-term evolution

(LTE), which are wireless communication access technologies. A

novel multiband antenna applicable in small handsets that cover

GSM900 and GSM1800/1900 (880960 and 17101880/1850

1990 MHz) as well as LTE2300 (23002400 MHz) and LTE2500

(25002690 MHz) is presented. The design of the proposed compact

multiband antenna is described in detail. The related fabricated results

for the obtained performances are presented and discussed.

Design of antennas: Fig. 1a shows the proposed multiband antenna

structure. The antenna was fabricated on an FR4 glass epoxy substratewith a thickness of 0.8 mm, relative permittivity of 4.4, and a loss

tangent of 0.02. The overall FR4 substrate was employed as the

system circuit board (122 60 mm2) on which the GSM/LTE antenna

(10 50 mm2) was designed for the top edge of a mobile phone. The

backside of the FR4 substrate was used as the system ground plane

(112 60 mm2). The selected dimensions of the overall circuit board

and the antenna are reasonable for practical mobile phones.

The proposed antenna is composed of a circuit structure directly con-

nected to a feeding contact for a monopole antenna and a coupled

ground strip connected to a shorting contact. The monopole strips are

designed to be approximately a quarter-wavelength long at 900, 1800,

2300, and 2500 MHz. A coupled ground strip is also added to

connect the right side of the lower bands and to obtain good impedance

matching across the operating bands. After adjusting the monopole

strips in the resonant modes, a low operating band of 840

960 MHzwas obtained for GSM900 applications. The high modes of 1800,

2300, and 2500 MHz constitute high operating bands of 1660

2670 GHz for GSM1800, GSM1900, LTE2300, and LTE2500 appli-

cations. The coupled ground strip includes comb-shaped dual-parasitic

shorted strips. The overall antenna is fed by a 50 microstrip line con-

nected to the feeding point (point A) of the driven monopole and a

coupled ground strip connected to the shorting point (point B) of the

system ground planes. All the optimised geometric parameters for the

multiband antenna element are presented in Fig. 1b. The proposed

microstrip line-fed antenna structure is easy to implement with a mono-

lithic microwave-integrated circuit and has dimensions that can be modi-

ed to match different antenna geometries for multiband impedance

characteristics.

Simulated and measured results: Fig. 2 shows the simulated andmeasured return losses of the proposed antenna. The experimental

results were obtained using an Agilent E8364A vector network analyser.

The simulation was conducted using high-frequency structure simulator

simulation software. The simulated and measured return losses are in

good agreement. The measured results based on a 6 dB return loss

cover the following bands: GSM900 (880960 MHz), GSM1800

(17101880 MHz), GSM1900 (18501990 MHz), LTE2300 (2305

2400 MHz), and LTE2500 (25002690 MHz). Fig. 2 also shows the

fabricated antenna with the ground plane.

direct-fed monopole

strip1

strip2

A : feeding pointB : shorting pointunit : millimetres

ground plane

112 60 mm2112

60

a

b

50

1

1.1

4

21.5

200.5

0.8

10

1.9 0.9 7

0.5

0.5

0.5

1.3

23

24.5

11.5

15.51.5

15.5

1018.5

19.9 1.5

2

6.5

3.5

1.5

18.4

0.817 1.4

strip3

coupled ground strip

Z

Y

X

A B

Fig. 1Geometry of microstrip line-fed structure for multiband antenna oper-ation in mobile phone, and detailed dimensions of metal pattern for multi-band antenna

a Geometryb Detailed dimensions

0

5

3 : 1 VSWR

top view bottom viewsimulated

measured

photographs of fabricated antenna

10

15

20

25

30

35

400.5 1.0 1.5

frequency, GHz

returnloss,

dB

2.0 2.5 3.0

Fig. 2Simulated and measured return loss of proposed antenna

Fig.3 shows the geometric comparison of the simulated return loss

for the proposed antenna. Three antennas have the same coupled

ground strip but different numbers and locations of monopole strips.

Case 1 only contains monopole strip 1 (antenna 1), whereas case 2 is

created by adding monopole strip 2 to case 1 (antenna 2). Case 1

involves two resonant modes at 1900 and 2400 MHz, and the imped-

ance matching is poor. In case 2, the impedance matching is good in the

resonant modes. In case 3, monopole strip 3 is added to the case 2 struc-

ture (antenna 3). Case 4 is the proposed antenna (antenna 4). The anten-

nas in cases 3 and 4 have roughly the same structure but different widthsof monopole strip 3. The width of monopole strip 3 is adjusted for

impedance matching, and a high-order mode occurs at 2.6 GHz.

These data indicate that the proposed antenna has a multiband

characteristic.

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0

5

103 : 1VSWR

strip1strip2

strip3

15

20

25

returnloss,

dB

30

35

40

0 0.5 1.0 1.5

frequency, GHz

proposedantenna-3

antenna-1antenna-1

antenna-2

antenna-3proposed

antenna-2

2.0 2.5 3.0

Fig. 3Geometric comparison of simulated return loss for proposed antenna

0

45

90

135

190

225

270

315

40 30 20 10 0

0

45

90

135

190

225

270

315

40 30 20 10 0

0

45

90

135

190

225

270

315

40 30 20 10 0

0

45

90

135

190

225

270

315

40 30 20 10 0

0

45

90

135

190

225

270

315

40 30 20 10 0

0

45

90

135

190

225

270

315

40 30 20 10 0

0

45

90

135

190

225

270

315

40 30 20 10 0

0

45

90

135

190

225

270

315

40 30 20 10 0

XZ-planeXY-plane

XZ-planeXY-plane

XZ-planeXY-plane

XZ-planeXY-plane

co-polar

cross-polar

a

b

c

d

Fig. 4Measured co-polarisation and cross-polarisation radiation patterns at900, 1800, 2300 and 2500 MHz

a 900 MHzb 1800 MHzc 2300 MHzd2500 MHz

The measured co-polarisation and cross-polarisation radiation pat-terns of the implemented antenna on the XY and XZ planes at four

frequencies are illustrated in Fig. 4. The far-eld radiation patterns of

the antenna were measured at resonant frequencies of 900, 1800,

2300, and 2500 MHz. The far-eld radiation patterns at different fre-

quencies were measured in an anechoic chamber. The far-eld radiation

measurements were obtained at various frequency points in the

GSM900/1800/1900/LTE2300 and LTE2500 bands to plot the

antenna peak gain and radiation efciency spectra shown in Fig. 5.

The measured antenna peak gain for the GSM900 band is 0.62

2.12 dBi, and the radiation efciency is 4254%, as shown in Fig.5a.

The measured antenna peak gain for the GSM1800/1900 bands is

2.383.81 dBi, and the radiation efciency is 4571%. The measured

antenna peak gain for the LTE2300/2500 bands is 3.824.79 dBi, and

the radiation efciency is >53%, as shown in Fig. 5b. These results

are acceptable for practical mobile phone applications.

6 8

7

6

5

4

3

3

100measured peak gain

measured efficiency

measured peak gain

measured efficiency

90

80

radiationefficiency,%

radiationefficiency,%

70

60

50

40

30

20

10

0

100

90

80

70

60

50

40

30

20

10

0

5

4

3

2

antennapeakgain,

dBi

antennapeakgain,

dBi

1

0

0.82 0.84 0.86 0.88 0.90 0.92frequency, GHz

a b

0.94 0.96 0.98 1.00 1.6 1.8 2.0 2.2 2.4 2.6 2.8

frequency, GHz

Fig. 5Measured peak gain and efciencya GSM900 bandb GSM1800/1900/LTE 2300/2500 bands

Conclusion: A planar GSM/LTE multiband antenna design for mobile

phones has been developed and veried. A direct-fed monopole antenna

and a coupled ground strip were utilised to realise ve operating bands

on a 6 dB return loss covering the GSM900/1800/1900/LTE2300/

2500 application bands. The good radiation characteristics of gain and

efciency illustrate the potential applications of the proposed antenna

for mobile phones. The footprint of the proposed antenna is only

500 mm2; thus, the antenna can be easily integrated into the system

circuit board of mobile phones. The fabrication procedure of the pro-

posed antenna is compatible with printed circuit board technology.

The Institution of Engineering and Technology 2015Submitted: 27 May 2015 E-rst: 27 July 2015

doi: 10.1049/el.2015.1839

One or more of the Figures in this Letter are available in colour online.

Yu-Jen Chou, Guo-Sheng Lin and Mau-Phon Houng (Institute of

Microelectronics, Department of Electrical Engineering, National

Cheng Kung University, Tainan, Taiwan)

E-mail: mphoung@mail.ncku.edu.tw

Jun-Fu Chen and Lih-Shan Chen (Department of Electronic

Engineering, I-Shou University, Kaohsiung, Taiwan)

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ELECTRONICS LETTERS 20th August 2015 Vol. 51 No. 17 pp. 13041306