REFERENCES

1. P.C. Hsu, C. Nguyen, and M. Kintis, Uniplanar broad-band push-

pull FET amplifiers, IEEE Trans Microwave Theory Tech 45

(1997), 2150–2152.

2. T.-H. Chen, K.W. Chang, S.B. Bui, H. Wang, G.S. Dow, L.C.T.

Lui, T.S. Lin, and W.S. Titus, Broadband monolithic passive

baluns and monolithic double-balanced mixer, IEEE Trans Micro-

wave Theory Tech 39 (1991), 1980–1986.

3. N. Marchand, Transmission line conversion transformers, Electron-

ics 17 (1944), 142–145.

4. S.-C. Tseng, C. Meng, C.-H. Chang, C.-K Wu, and G.-W. Huang,

Monolithic broadband Gilbert micromixer with an integrated

Marchand balun using standard silicon IC process, IEEE Trans

Microwave Theory Tech 54 (2006), 4362–4371.

5. K. Zoschke, M.J. Wolf, M. Topper, O. Ehrmann, T. Fritzsch, K.

Kaletta, F.-J. Schmuckle, and H. Reichl, Fabrication of application

specific integrated passive devices using wafer level packaging

technologies, IEEE Trans Adv Packag 30 (2007), 359–368.

6. C. Wang, J.-H. Lee, and N.-Y. Kim, High-performance integrated pas-

sive technology by advanced SI-GaAs-based fabrication for RF and

microwave applications, Microwave Opt Tech Lett 52 (2010), 618–623.

7. H.M. Greenhouse, Design of planar rectangular microelectronic

inductors, IEEE Trans Parts Hybrids Packag 10 (1974), 101–109.

8. F.W. Grover, Inductance calculations, Van Nostrand, New York, 1962.

9. C.P. Yue and S.S. Wong, Physical modeling of spiral inductors on

silicon, IEEE Trans Electron Device 47 (2000), 560–568.

10. W.R. Eisenstadt, B. Stengel, and B.M. Thompson, Microwave dif-

ferential circuit design using mixed-mode S-parameters, Wiley,

New York, 2001.

11. Y.J. Yoon, Y. Lu, R.C. Frye, and P.R. Smith, Spiral transmission-

line baluns for RF multichip module packages, IEEE Trans Adv

Packag 22 (1999), 332–336.

12. Y.J. Yoon, Y. Lu, R.C. Frye, and P.R. Smith, A silicon monolithic

spiral transmission line balun with symmetrical design, IEEE Elec-

tron Device Lett 20 (1999), 182–184.

13. J.-Y. Ihm and K.-P. Hwang, RF balun embedded in multiplayer or-

ganic substrate, Microwave Opt Tech Lett 49 (2007), 473–475.

VC 2011 Wiley Periodicals, Inc.

A COMPACT MULTIBAND ANTENNA FORWLAN AND WiMAX APPLICATIONS

Chen Wang, Ping Xu, Bo Li, and Ze-Hong YanNational Key Laboratory of Science and Technology on Antennasand Microwaves, Xidian University, Xi’an, People’s Republic ofChina; Corresponding author: wangchen@mail.xidian.edu.cn

Received 12 December 2010

ABSTRACT: A compact printed monopole antenna applied to wirelesslocal area network (WLAN) and worldwide interoperability formicrowave access (WiMAX) applications is proposed. By combining a

C-shaped strip and two L-shaped strips, fed by a 50-X microstriptransmission line, multiple impedance bandwidths covering WLAN/2.4/

5.2/5.8 and WiMAX/3.5 are obtained. Further, the proposed antennaoccupies a small size of 35 � 20 mm2, and has good radiationcharacteristic and peak gains to be 2.77, 2.92, and 3.04 dBi at 2.45,

3.5, and 5.5 GHz, respectively. VC 2011 Wiley Periodicals, Inc.

Microwave Opt Technol Lett 53:2016–2018, 2011; View this article

online at wileyonlinelibrary.com. DOI 10.1002/mop.26183

Key words: multiband antenna; WLAN application; WiMAXapplication; compact size

1. INTRODUCTION

Recently, wireless communications have been developed widely

and rapidly, which leads to a great demand in designing low-

profile and multiband antennas for mobile terminals [1–6].

Many antennas, such as the integrated F-shaped antenna, the

coupling-fed printed antenna, and the CPW-fed G-shaped

antenna, cover only 2.4/5-GHz WLAN bands [1–3]. In [4], the

compact triple-band antenna is obtained for WLAN and

WiMAX applications; however, the radiation performance is not

so good at the upper band owing to its asymmetric structure. In

[5, 6], the printed trident-shaped antenna and the wideband

asymmetric hybrid antenna have good impedance characteristics,

Figure 1 Geometry of proposed antenna: (a) top view, (b) bottom view, and (c) side view

2016 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 53, No. 9, September 2011 DOI 10.1002/mop

but the overall dimensions of these antennas are somewhat

large.

In this article, we propose a compact multiband antenna cov-

ering the operating bands of both wireless local area network

(WLAN) at 2.45 GHz (2400–2484 MHz), 5.2 GHz (5150–5350

MHz), and 5.8 GHz (5725–5825 MHz) and worldwide interoper-

ability for microwave access (WiMAX) at 3.5 GHz (3300–3700

MHz). The proposed antenna has an overall dimension of 35 �20 � 1.6 mm3. And by adjusting the dimensions of the strips

and the ground plane, broad impedance bandwidth and similar

omnidirectional radiation patterns suitable for WLAN and

WiMAX can be achieved. Details of the antenna design and ex-

perimental results are presented in the following sections.

2. ANTENNA DESIGN

The configuration of the proposed antenna is shown in Figure 1.

The proposed antenna is etched on an inexpensive FR4 substrate

of dielectric constant er ¼ 4.4 and substrate thickness H ¼ 1.6

mm, with the dimension of 35 � 20 mm2 (L � W). And, in this

antenna design, a 50-X microstrip line serves as the feeder. The

multiresonant modes of the proposed antenna are obtained from

the multiresonant structures of different dimensions. From Figure

1, it can be seen that the three resonant paths, which consist of

one C-shaped strip (L2 þ L3 þ L4 þ L5) and two L-shaped strips

(L2 þ L7 þ L8 and L2 þ L6), are set close to a quarter-wave-

length at 2.45, 3.5, and 5.5 GHz, respectively. All the strips are

designed into a stepped pattern for broad bandwidth. Furthermore,

the plane (D � Lg2) is added to the conventional ground plane

(W � Lg1) on the other side of the substrate for improving the

impedance matching of the 5.5 GHz band. The antenna was

simulated using EM software (HFSS.11). The optimal antenna pa-

rameters are set as follows: L1 ¼ 18.5 mm, L2 ¼ 3.5 mm, L3 ¼13 mm, L4 ¼ 5 mm, L5 ¼ 6.9 mm, L6 ¼ 6 mm, L7 ¼ 3 mm,

L8 ¼ 8.5 mm, W1 ¼ 3.5 mm, W2 ¼ 2 mm, W3 ¼ 0.5 mm, W4 ¼3 mm, W5 ¼ 3.5 mm, W6 ¼ 2.8 mm, W7 ¼ 0.5 mm, W8 ¼1 mm, Lg1 ¼ 13 mm, Lg2 ¼ 3.5 mm, and D ¼ 9.5 mm.

3. RESULTS AND DISCUSSION

The proposed antenna was simulated and optimized. The S pa-

rameters were measured with WILTRON37269A vector network

analyzer. The simulated and measured S11 against frequency for

the antenna are shown in Figure 2. It can be seen that the meas-

ured results reasonably agree with the simulated results with an

acceptable frequency discrepancy. For S11 < �10 dB, the meas-

ured impedance bandwidths are about 120 MHz (2.38–2.50

GHz), 690 MHz (3.20–3.89 GHz), and 2710 MHz (5.10–7.81

GHz), covering WLAN/2.4/5.2/5.8 and WiMAX/3.5 bands.

Figure 2 Simulated and measured S11 of the proposed antenna

Figure 3 Simulated S11 characteristic of the proposed antenna for vari-

ous L5

Figure 4 Simulated S11 characteristic of the proposed antenna for vari-

ous L6

Figure 5 Simulated S11 characteristic of the proposed antenna for vari-

ous L8

DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 53, No. 9, September 2011 2017

Parametric studies were performed to quantify the effects of

lengths L5, L6, and L8 on S11 of the proposed antenna, as shown

in Figures 3, 4, and 5. From Figure 3, it can be seen that, by

increasing the strip length L5, the lower band of the antenna can

be excited at lower frequencies. However, smaller effects of the

strip length L5 for the middle and upper band are seen. The S11

for different values of L6 are shown in Figure 4. It is observed

that the upper resonant frequency band is mainly affected by

changes in L6. Besides, it is discovered that the middle resonant

frequency band is very sensitive to the strip length L8 from Fig-

ure 5. From the results obtained, the strip lengths L5, L6, and L8

are selected to be 6.9, 6, and 8.5 mm, respectively.

The radiation characteristics of the proposed antenna were

studied through measurement. The measured radiation patterns

at the frequencies 2.45, 3.5, and 5.5 GHz are shown in Figures

6, 7, and 8, respectively. The measured results show good simi-

lar omnidirectional radiation in the azimuth plane (x–y plane),

although the antenna has an asymmetrical configuration. The

peak gains of the proposed antenna are 2.77, 2.92, and 3.04 dBi

at 2.45, 3.5, and 5.5 GHz, respectively, as shown in Figure 9.

4. CONCLUSIONS

A compact printed monopole antenna with a C-shaped strip and

two L-shaped strips for WLAN and WiMAX applications has

been presented. The impedance characteristic to meet the

requirements of WLAN in the 2.4/5.2/5.8 GHz bands and

WiMAX in the 3.5 GHz band is achieved. Also, the nearly

omnidirectional radiation patterns in the azimuth plane are

measured. Because of its low cost, light weight, and compact

size, the antenna is very suitable for multiband wireless commu-

nication applications.

REFERENCES

1. S.H. Yen and K.L. Wong, Integrated F-shaped monopole antenna

for 2.4/5.2 dual-band operation, Microwave Opt Technol Lett 34

(2002), 24–26.

2. Z.Y. Zhang, G. Fu, and S.L. Zuo, A compact printed monopole

antenna for WLAN and WiMAX applications, Microwave Opt

Technol Lett 52 (2010), 857–861.

3. S. Kim, J. Choi, and Y. Kim, CPW-feed broadband G-shaped

monopole antenna for dual-band WLAN applications, Microwave

Opt Technol Lett 48 (2006), 2310–2311.

4. J.F. Huang, M.T. Wu, and J.Y. Wen, A compact triple-band

antenna design for UMTS, WLAN and WiMAX applications,

Microwave Opt Technol Lett 51 (2009), 2207–2212.

5. J.R. Panda and R.S. Kshetrimayum, A printed trident shaped triple-

band monopole antenna for wireless applications, 2010 International

Conference on Signal Processing and Communications, (2010),1–5.

6. S.Y. Lee and C.C. Yu, A novel wideband asymmetric hybrid

antenna for WLAN/WiMAX applications, Microwave Opt Technol

Lett 51 (2009), 1055–1057.

VC 2011 Wiley Periodicals, Inc.

Figure 6 Measured radiation pattern at 2.45 GHz of the proposed

antenna

Figure 7 Measured radiation pattern at 3.5 GHz of the proposed antenna

Figure 8 Measured radiation pattern at 5.5 GHz of the proposed

antenna

Figure 9 Peak gains of the proposed antenna

2018 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 53, No. 9, September 2011 DOI 10.1002/mop