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VC 2010 Wiley Periodicals, Inc.

BROADBAND DUAL-FREQUENCYSPIDER-SHAPED PRINTED DIPOLE

ANTENNA FOR WLAN APPLICATIONS

Xiumei Shen, Yingzeng Yin, Chengyue Su, and Shaoli ZuoAntenna Institution, Xidian University, Xian, China; Correspondingauthor: meizijidian@163.com

Received 14 June 2009

ABSTRACT: A novel broadband dual-frequency spider-shaped dipole

antenna for 2.4/5.2 GHz wireless local area networks (WLAN) is

proposed. The antenna consists of a double-sided printed dipole, whose

long arms and short center-stubs can produce dual bands and lead to

good impedance matching in a wide dual-band without external

matching circuitry. For the experimental study, excellent performance

for operating frequencies across 22403260 MHz and 47005970 MHz

bands has been observed. Good radiation characteristics of dipole-like

patterns, and 2.6- and 4.6-dBi peak antenna gains for the lower and

upper bands, respectively, have been obtained. And this antenna could

be easily printed and integrated on the system circuit board for WLAN

applications. VC 2010 Wiley Periodicals, Inc. Microwave Opt Technol

Lett 52: 917919, 2010; Published online in Wiley InterScience

(www.interscience.wiley.com). DOI 10.1002/mop.25041

Key words: spider-shaped; printed dipole antenna; WLAN; dual-band

1. INTRODUCTIONWith the rapid development of the wireless communications, the

multiband operations are in great demand, especially for the

wireless local area network (WLAN) standards, such as IEEE

802.11b/g (24002484 MHz) and IEEE 802.11a (51505950

MHz) bands. Many applications are designed and implemented

to satisfy varying regulations and spectrum availability in vari-

ous parts of the world. To make mobile WLAN devices work

with all these standards, antennas for WLAN operation are nec-

essary and developed. Planar monopoles [1, 2] printed inverted-

F antennas [3, 4] have been proposed for WLAN applications.

Recently, various types of printed dipole antennas (PDAs) have

been also studied to meet the increasing trend for wideband

WLAN antennas, and several techniques for size reduction and

bandwidth enhancement have been proposed [5, 6]. In particular,

the double-sided PDA is one of these techniques in case of mul-

tiband operation [6], which is an easy fabricated and simple

structure with easy integration into solid-state devices.

In this article, a novel design of a spider-shaped antenna for

2.4/5.2 GHz dual-band applications is presented. The antenna

uses a pair of printed spider-shaped dipoles, which can com-

pletely cover the two standards IEEE WLAN with compact size.Compared with the single layer antenna, the double-sided

printed antenna can obtain better impedance matching and iso-

tropic radiation pattern. The antenna has not only dual bands

characteristics but also could be matched well without external

matching circuitry in quite wide frequency ranges. Good fre-

quency responses, radiation patterns, and antenna gains are also

observed and discussed.

2. ANTENNA DESIGN

Figure 1 shows the geometry and structure of the presented spi-

der-shaped dipole antenna for WLAN applications. The antenna

consists of two dipoles printed on top and back surfaces of the

substrate, respectively. As a matter of fact, these two dipoles are

identical except the center parts. The top layer comprises two

Figure 1 Top (a) and bottom (b) layout of the spider-shaped antenna

(unit: mm)

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coplanar flower-shaped elements, which are placed oppositely to

each other. Figure 2 shows the simulated surface current for the

proposed compact dual-band antenna. As we can see that the

long dipole branch 1 is for generating the lower operating mode

at 2.4 GHz. And the short branches are for obtaining the upper

operation mode at about 5.2 GHz. These short branches 2 and 3

(placed on top and back layers) with different shape and length

could produce two near resonance modes. The unit of these two

modes can form the wide upper operating band of the antenna.

The top and back units are connected together by four copper

cylinders with radius of 0.5 mm. The branch 1 of the spider-

shaped antenna can broaden the surface dimensions of the radia-

tion elements. So, the horizontal currents distributions are devel-

oped. Thereby, the impendence bandwidth of the lower fre-quency can be extended too.

Figure 1 also shows the back layer geometry, which is

slightly different from the top one. The rectangular stub of this

layer can also be a matching section. By adjusting the variation

Figure 2 The simulated surface current for the proposed antenna (a)

f_2400 MHz; (b) f_5200 MHz. [Color figure can be viewed in the online

issue, which is available at www.interscience.wiley.com]

Figure 3 The prototype of the proposed antenna. [Color figure can be

viewed in the online issue, which is available at www.interscience.

wiley.com]

Figure 4 Simulated and measured return loss of the spider-shaped

antenna. [Color figure can be viewed in the online issue, which is avail-

able at www.interscience.wiley.com]

Figure 5 Measured E-plane (x-z plane) and H-plane (y-z plane) radia-

tion patterns for the proposed antenna in Figure 2: (a) f_2400 MHz;

(b) f_5200 MHz. [Color figure can be viewed in the online issue, which

is available at www.interscience.wiley.com]

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7.710 mm, a better impendence matching can be obtained at

the upper operated frequency.

The structure of the simplified feed for a PDA with a coaxial

line is shown in Figure 3, which is printed on an FR4 substrate

of thickness h 1 mm and relative permittivity of 4.4. The

antenna has dimension of 34 mm 48 mm needs no external

matching circuitry to obtain good impendence matching for the

two desired operating bands. In addition, by properly adjusting

the distance between the two flower-shaped elements, good cou-

pling can be achieved. The best distance is 2 mm via iterative

experiment.

3. EXPERIMENTAL RESULTS AND DISCUSSION

The proposed spider-shaped antenna for WLAN applications has

been simulated by Ansoft HFSS software. The prototype (see

Fig. 3) is fabricated and experimentally analyzed. Figure 4

shows the simulated and experimental results of the return loss

for the antenna design of Figure 1. It is clearly seen that good

agreement between the measured and simulated results is

obtained. From the results, the lower band has a bandwidth

(1:2.0 VSWR or about 10.0-dB return loss) of 22403260 MHz,

covering the required IEEE 802.11b/g (24002484 MHz). For

the upper band, by only using two different branches (i.e.,

branches 2 and 3), a bandwidth of 42305970 MHz is obtained

and can provide the required bandwidth for the IEEE 802.11a

(51505950 MHz) bands. However, due to the feeding cable,

there are discrepancy between the simulated and measured

results at upper band.

The radiation characteristics of the proposed antenna are also

studied. The measured radiation patterns of both copolarization

and cross-polarization for the frequency at 2.4, 5.2 GHz are

shown in Figure 5. As expected, the radiation patterns at the

two frequencies are close to those of the conventional half-wavelength center-fed dipole antenna. However, there is slight

nonroundness existing at the H-plane, which is mainly due to

the effect of the feeding cable. Figure 6 shows the measured

peak gains of the proposed spider-shaped dipole antenna across

two operating bands. Peak gains for both the two operating

bands are measured to be 2.7 and 4.6 dBi, respectively.

4. CONCLUSIONS

A dual-band spider-shaped dipole antenna for the WLAN appli-

cations has been designed, fabricated, simulated, and tested.

Simulation and experimental results showed good agreement

with each other. The proposed antenna exhibits two wide bands,

covering the 2.4 GHz (22403260 MHz) and 5 GHz (4270

5950 MHz) WLAN bands without external matching network.Over the wide operating band, stable radiation characteristics

have also been obtained. The antenna has wide use in potential

applications for WLAN or other wireless systems that work in

these bands.

REFERENCES

1. M.J. Ammann and Z.N. Chen, Wideband monopole antennas for

multi-band wireless systems, IEEE Antennas Propag Mag 45

(2003), 146150.

2. N.P. Argawall, G. Kumar, and K.P. Ray, Wideband planar monop-

ole antennas, IEEE Trans Antennas Propag 46 (1998), 294295.

3. A.C.W. Wong and W.H. Leung, Integrated Inverted F Antenna and

Shield Can, U.S. Patent 6,850,196 B2, Feb. 1, 2005.

4. D. Nashaat, H.A. Elsadek, and H. Ghali, Dual-band reduced size

PIFA antenna with U-slot for bluetooth and WLAN applications,

IEEE Trans Antennas Propag 2 (2003), 962965.

5. Y.H. Suh and K. Chang, Low cost microstrip-fed dual frequency

printed dipole antenna for wireless communications, Electron Lett

36 (2000), 11771179.

6. H.-M. Chen, J.-M. Chen, P.-S. Cheng, and Y.-F. Lin, Feed for

dual-band printed dipole antenna, Electron Lett 40 (2004).

VC 2010 Wiley Periodicals, Inc.

A COMPACT TRI-BAND PIFA ANTENNAFOR WLAN AND WiMAX APPLICATIONS

Shaoli Zuo, Yingzeng Yin, Zhiya Zhang, and Weijun WuKey Laboratory of Antennas and Microwave Technology, XidianUniversity, Xian, Peoples Republic of China; Correspondingauthor: zuoshaoli@163.com

Received 19 June 2009

ABSTRACT: A tri-band planar inverted-F antenna (PIFA) for WLAN

and WiMAX applications is proposed. By combining F-T-shaped slots in

the radiating structure and using a trapezoidal feeding plate, three

resonant modes are generated and impedance bandwidth of the antenna

is enhanced. The fabricated radiation patch has a compact size of 25

11 8 mm3 with a rectangular ground plate of 26 40 mm2. For S11

Figure 6 Measured gain vs. operating frequency for the proposed

antenna (a) f_2400 MHz; (b) f_5200 MHz

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