IMPEDANCE MATCHED COMPACT ZIGZAG MULTIBAND INVERTED-F ANTENNA FOR WI-FI, MOBILE WIMAX, BLUETOOTH AND WLAN OPERATIONS IN PORTABLE DEVICES

International Journal of Ad hoc, Sensor & Ubiquitous Computing (IJASUC) Vol.2, No.1, March 2011
DOI : 10.5121/ijasuc.2011.2108 86
IMPEDANCE MATCHED COMPACT ZIGZAG
MULTIBAND INVERTED-F ANTENNA FOR WI-FI,
MOBILE WIMAX, BLUETOOTH AND WLAN
OPERATIONS IN PORTABLE DEVICES
S.M. Shibbir Alam#*1
, Md. Selim Hasan#*2
, Bulbul Ahmed#+3
,Md. Kafil Uddin≠+4
#
Department of Electrical & Electronic Engineering, *Khulna University of Engineering
and Technology, Khulna, Bangladesh
1
smsa_kuet@yahoo.com,2
selim.hasan@grameenphone.com
+
Rajshahi University of Engineering & Technology, Rajshahi, Bangladesh
3
engr_raaz95@yahoo.com
≠
Department of Electronics & Telecommunication Engineering
4
kafil.uddin@grameenphone.com
ABSTRACT
Multiband loaded inverted-F antennas suitable to be applied in a portable device as an internal antenna
having high gain property for mobile WiMAX , Wi-Fi, Bluetooth and WLAN operations are presented.
Numerical simulation is carried out using method of moments in Numerical Electromagnetic Code
(NEC-2). The proposed dual inverted-F antenna is suitable for 3.5/5 GHz and compact triple band
inverted-F antenna is for 2.4/3.5/5.2 GHz operations. Total areas occupied by the antennas are
24mm×37mm and 29mm×37mm in case of dual IFA and triple IFA respectively. The antennas contain
an incredibly high peak gain of 7.72 dBi at 5 GHz band and the gain variations at all frequency bands
are less than 1 dBi . In addition, the antennas have satisfactory radiation characteristics at all the
frequency bands. Due to compact area occupied, the proposed antennas are promising to be embedded
within the different portable devices.
KEYWORDS
Inverted-F Antenna, WiMAX, Wi-Fi, WLAN, Bluetooth
1. INTRODUCTION
Wireless communications have been developed widely and rapidly in the modern world
especially during the last decade. In the near future, the development of the personal
communication devices will aim to provide image, DMB (Digital Multimedia Broadcasting)
video telephony, speech and data communications at any time-anywhere around the world using
the WLANs (Wireless Loca Area Networks). Rapid advances of various WLAN protocols have
sparked the requirement for miniaturized multiband antennas with suitable frequency bands
appropriate for the Wi-Fi (IEEE 802.11 standard) and mobile WiMAX (IEEE 802.16e-2005
standard) applications are highly desirable. Bluetooth and WLAN operate in 2.4 GHz industrial,
scientific and medical (ISM) band (frequency range 2.4–2.5 GHz) and unlicensed national
information infrastructure (U-NII) band used in WLAN, Bluetooth and Wi-Fi operation. This
U-NII band can be divided into three sub-bands as U-NII low (frequency ranges 5.15–5.35
GHz), U-NII mid (frequency range 5.47–5.725 GHz) and U-NII high (frequency range 5.725–
5.875 GHz), which offers more non-overlapping channels than the channel offered in the ISM

87
frequency band. On the other hand, IEEE 802.16e-2005 standard named mobile WiMAX
provides maximum of 10 Mbps wireless transmission of data using variety of transmission
modes from point to multipoint links to portable and fully mobile internet access devices.
WiMAX is a possible replacement for cellular technologies such as global system for mobile
(GSM) communication, code division multiple access (CDMA) or can be used as an overlay to
increase capacity. It has also been considered as a wireless backhaul technology for 2G, 3G and
4G networks in both developed and poor nations. Mobile WiMAX operating bands are 2.3 GHz
(frequency range 2.3–2.4 GHz), 2.5 GHz (frequency range 2.5–2.7 GHz) and 3.5 GHz
(frequency range 3.4–3.6 GHz). To provide seamless internet access for the mobile devices a
dual band antenna for Wi-Fi, mobile WiMAX and WLAN operation is necessary.
All the antennas, i.e., monopole antenna, slot antenna, flat-plate antenna and L-slit antenna
provides Wi-Fi operation at 2.4 and 5 GHz frequency bands which is not suitable for the
operation of mobile WiMAX frequency band. Uni-planar dual band monopole antenna provides
two operating frequency bands for Wi-Fi operation with near about 3 and 5.5 dBi gain at
frequency 2.4 and 5.8 GHz respectively [1]. If the monopole antenna is designed in hook shaped
the gain is not over 2.8 and 4.29 dBi at frequency 2.4 and 5 GHz respectively [2]. Moreover,
dual band slot by using two linear slot are arranged to be close, equilateral triangular slot
antenna, compact double L-slit or compact dual band slot antenna has the moderate gain in both
frequencies but the antenna geometry are not simple[3]-[6]. The gain of the flat-plate antenna
with shorted parasitic element also limited to 3 dBi at 2.4 GHz and 5.5 dBi at 5.2/5.8 GHz
operating frequency [7].Compact loop type Antenna [8] and compact monopole antenna [9]
have been proposed recently but they are unable to provide the 3.5 GHz mobile WiMAX
operation. However, modified two-strip monopole antenna [10] can provide 3.5 GHz operation
but the antenna geometry is not simple.
It is realized that some low-profile microstrip and printed slot antennas are required for Wi-Fi
and mobile WiMAX operations which can overcome the constraints of size, weight, cost,
performance, installation complexity and aerodynamic profile. To ensure all the mentioned
requirements, inverted-F antenna is one of the good candidates. Inverted-L antenna suffers from
lower input impedance than PIFA and slot antennas. In this paper, we present high gain slightly
loaded and moderately loaded IFA to support dual and triple band operation.
2. ANTENNA DESIGN
In designing multiband antenna for Wi-Fi, mobile WiMAX and WLAN operation, we examine
the possibility of increasing antenna gain with simplified structure. Using method of moments
(MoM’s) in Numerical Electromagnetic Code (NEC) [11 ], we conducted parameter studies to
ascertain the effect of different loading on the antenna performance to find out the optimal
design. For our study we assume the copper conductor and the antenna was intended to be
matched to 50 ohm system impedance. The geometrical configuration of the inverted-F
antennas are depicted in Fig. 1.

88
(a) (b) (c)
Figure 1. Geometry of (a) IFA (b) dual IFA (c) Triple IFA
In case of IFA as shown in Figure 1(a), the resonant frequency related to w given as [12]
Where c is he speed of light. The effective length of the current is l+t+h1+w. Under this case the
resonant condition can be expressed as
l+t+h1+w
The other resonant frequency that is a part of linear combination with the case 0< w<( l+ t ) and
expressed as
The resonant frequency (fr ) is a linear combination of resonant frequency associated with the
limiting case. For the antenna geometry of figure 1 (a) fr can be written from equation (1) and
(2) as [34]
fr =r.f1+(1-r)f2
Where r= w / (l+ t)
For the analysis of the accuracy optimum segmentation of each geometrical parameter are used
in NEC. Figure 1 (a) represents the basic geometry of the IFA. Here one leg of IFA directly
connected to the feeding and another leg spaced s from the ground plane. For the simulation we
consider portable circuit board (PCB) with permittivity of εr= 2.2 and substrate thickness of
1.58 mm. The antenna is assumed to feed by 50 ohm coaxial conductor, with its central
conductor connected to the feeding point and its outer conductor soldered to the ground plane
just across the feeding point. In the analysis the dimensions of the ground plane considered as
60 mm × 60 mm.
It is observed that when a load is applied to the single band IFA, the antenna can operate in two
bands namely 3.5 GHz and 5 GHz frequency bands. It is shown in Fig. 1(b). We further studied
on this antenna to increase the bands.We applied another zigzag load on the dual band IFA and
at this time the antenna can effectively cover 2.4/3.5/5.2 WiFi/mobile WiMAX frequency
bands with satisfactory return loss and radiation characteristics. The geometrical configuration
(1)
(2)
(3)
(4)

89
of the proposed zigzag triple band inverted-F antenna is depicted in Fig. 1(c) and the design
parameters are listed in Table 1.
Table 1. Dimensions of the antennas
Antenna name Partameters Values (mm) Dimension(mm2
)
IFA
l 31
14 ×37
t 6
h 14
h1 13.6
w 2
s 0.4
Dual IFA
(Proposed)
l 31
24×37
l1 33
t 6
t1 4
h 14
h1 13.6
h2 5
w 2
s 0.4
Triple IFA
(proposed)
l 31
29×37
l1 33
L 37
t 6
t1 4
h1 13.6
h2 5
w 2
s 0.4
3. SIMULATION AND RESULTS
The simulated return losses of the proposed slightly loaded dual IFA(geometry of Figure 1 (b))
and moderately loaded triple IFA (geometry of Figure 1 (c)) are shown in Figure 2& 3. From
the simulation results, the slightly loaded IFA has return loss bandwidth of 250 MHz
(frequency ranges 3400 – 3650 MHz) at lower operating band and 1050 MHz (frequency ranges
5150 – 6200 MHz) at upper operating band. The lower operating band covers the 100 % of 3.5
GHz (IEEE 802.16e-2005 standard) mobile WiMAX (3.4 – 3.6 GHz) operating band. On the
other hand, the upper operating band covers the 100 % of 5 GHz (IEEE 802.11a standard) WiFi
(5.15– 5.875 GHz) operating band. Due to the increase in load to the IFA, the modified
moderately loaded IFA has an additional band (2.4 GHz) with improved return loss and gain
characteristics. Moderately loaded IFA has lower band return loss bandwidth of 150 MHz (2450
– 2600 MHz) which fully occupy the 2.4 GHz WiFi and Bluetooth/WLAN operating band.
The middle band shows a bandwidth of 100 MHz (3475 – 3575 MHz) covering the 3.5 GHz
for mobile WiMAX operating band (IEEE 802.16e-2005 standard). The upper band shows a
wider bandwidth of 925 MHz (4750 – 5675 MHz) covering the 5 GHz band for the Wi-Fi
operation (IEEE 802.11a standard). The variations of voltage standing wave ratio (VSWR) as a

90
function of frequency are shown in Figure 4 for both all operating bands. From the obtained
results, as the load applied to the IFA, the VSWR improves significantly and appear close to
standard value 1 in both antenna return loss bandwidth.
(a)
(b) (c)
Figure 2: Antennas return loss of dual IFA (a) as a function of frequency (b) lower return loss
bandwidth and (c) upper return loss bandwidth
(a)

91
(b) (c) (d)
Figure 3: Antennas return loss of triple IFA (a) as a function of frequency (b) lower return loss
bandwidth (c) middle return loss bandwidth (d) upper return loss bandwidth
(a) (b)
Figure 4: Variation of VSWR of the antennas as a function of frequency for
(a) dual IFA (b) triple IFA
Figure 5 represents the antennas input impedance variation and Figure 6 represents the antennas
phase shift causes due the impedance mismatch as a function of frequency. From the obtained
results, moderately loaded IFA has much better antenna input impedance than rest two
structures .Also, from the simulation study, the phase shift decrease with the application of load
to the IFA.

92
(a) (b)
Figure 5: Input impedance variation with respect to the frequency for
(a) dual IFA and (b)triple IFA
Fig 7 shows the total antenna gain for dual IFA at 3.5 and 5 GHz bands respectively. It is
found that in the 3.5 GHz band , the peak gain is about 7.49 dBi and less than 0.3 dBi of gain
variation is observed. In the 5 GHz band, the peak gain reaches about 7.72 dBi and gain
variation is less than about 2 dBi . Fig 8 shows the total antenna gain for triple IFA at 2.4,
3.5 and 5.2 GHz respectively. In the 2.4 GHz band, the peak gain is about 3.82 dBi and about
0.1 dBi of gain variation is observed. In the 3.5 GHz band, the peak gain reaches about 6.15
dBi and gain variation is about 1.3 dBi. In case of 5.2 GHz band, peak gain is 4.3 dBi with
only 0.9 dBi gain variations. Therefore both the antennas have stable gain at all the operating
bands and satisfied the required gain variation for the mobile WiMAX and Wi-Fi operation.
(a) (b)
Figure 6: Phase shift of the antennas as a function of frequency for
(a) dual IFA and (b) triple IFA

93
(a)
(b) (c)
Figure 7: Variation of antenna gain as a function of frequency for dual IFA
(a) Total gain (b) 3.5 GHz band (c) 5 GHz band
(a)

94
(b) (c) (d)
Figure 8: Variation of antenna gain as a function of frequency for triple band IFA
(a) Total gain (b) 2.4 GHz band (b) 3.5 GHz band (c) 5.2 GHz band
The radiation patterns of the proposed dual band IFA at the two resonant frequencies 3.5 & 5
GHz are illustrated in figure 9 and 10 in both vertical and horizontal plane respectively. For the
proposed triple IFA the radiation patterns at 2.4, 3.5 & 5.2 GHz frequencies are shown in figure
11 ,12and 13. From the obtained radiation pattern, the slightly loaded IFA has good radiation
characteristics in both planes at both operating frequencies and also the moderately loaded triple
IFA has acceptable radiation characteristics at all the operating frequency bands in horizontal
and vertical planes. At 5.2 GHz Wi-Fi operation, the antenna has somewhat less omnidirectional
gain pattern but it is full omnidirectional at other frequency bands.
(a) (b)
Figure 9: Total gain patterns of the proposed dual IFA at 3.5 GHz in
(a) Vertical plane (b) horizontal plane
(a) (b)
Figure 10: Total gain patterns of the proposed dual IFA at 5 GHz in

95
(a) (b)
Figure 11: Total gain patterns of the proposed triple IFA at 2.4 GHz in
(a) (b)
Figure 12: Total gain patterns of the proposed triple IFA at 3.5 GHz in
(a) (b)
Figure 13: Total gain patterns of the proposed triple IFA at 5 GHz in
4. CONCLUSIONS & FUTURE WORK
Multiband slightly and moderately loaded inverted-F antennas have been proposed and analyzed
by means of numerical simulations using MOM’s in NEC. The antennas geometry analyzed by
varying the four major geometry parameters (length, height, tap distance and spacing). For both
antennas, spacing has significant influence on the lower operating band while it has negligible
effect on the upper band. From the four parameters analysis antenna geometry chosen and
proposed antennas performance parameters are analyzed for multiband operations. The
proposed antennas have high gain for mobile WiMAX, WLAN, Bluetooth and Wi-Fi operation.
It is also observed that improvements in antenna gain, input impedance, phase shift and return

96
loss have been obtained when structured load is applied to the IFA. The antennas are of small
size and good radiation characteristics. Due to the compact area occupied, the proposed
antennas are promising to be embedded within the different mobile devices employing mobile
WiMAX, Wi-Fi, Bluetooth and WLAN operation.
Our future target is miniaturization of the proposed antennas with increasing operating
bandwidth and gain.
REFERENCES
[1] L. C. Chou, and K. L. Wong. “Uni-planar dual-band monopole antenna for 2.4/5 GHz WLAN
operation in the laptop computer.” IEEE Transactions on Antennas and Propagation. Vol. 55. No. 12. pp.
3739-37411. 2007.
[2] C. H. Lee and S. O. Park.” A compact printed hook-shaped monopole antenna for 2.4/5 GHz
WLAN applications.”Microwave and Optical Technology Letters.Vol.48. No.2. pp. 327-329. 2006.
[3] C. M. Su, H. T. Chen, F. S. Chang, and K. L. Wong. “Dual band slot antenna for 2.4/5.2 GHz
WLAN operation.” Microwave and Optical Technology Letters.Vol. 35. No. 4. pp. 306-308. 2002.
[4] Jeun-Wen Wu. “2.4/5 GHz dual band triangular slot antenna with compact operation.”
Microwave and Optical Technology Letters .Vol. 45. No. 1. pp. 81-84. 2005.
[5] W. Ren .”Compact dual band slot antenna for 2.4/5 GHz WLAN applications.” Progress in
Electromagnetic Research B. Vol. 8. pp. 319-327. 2008.
[6] T. H. Kim, and D. C. Park. “Compact dual-band antenna with double L-slits for WLAN
operation.” IEEE Antennas and Wireless Propagation Letters. Vol. 4. pp. 249-252. 2005.
[7] K. L. Wong, L. C. Chou, and C. M. Su. “Dual band flat plate antenna with a shorted parasitic
element for laptop applications.” IEEE Transactions on Antennas and Propagation. Vol. 53. No. 1. pp.
539-544. 2005.
[8] Yong-sun Shin and Seong-Ook Park. “A Compact loop type antenna for bluetooth, S-DMB,
Wibro, WiMax and WLAN applications.” IEEE Antennas and Wireless Propagation Letters . Vol. 6 .
February 2007.
[9] Jinwoo Jung ,Hyeonjin Lee and Yeongseog Lim. “Compact monopole antenna for dual ISM-
bands (2.4 and 5.8 GHz ) operation” .Microwave and Optical Technology Letters. Vol.51. No.9.
September 2009.
[10] Kwok L. Chung, T. H. Mak and W. Y. Tam. “A modified two-strip monopole antenna for Wi-Fi
and WiMAX applications.” Microwave and Optical Technology Letters. Vol.51. No.12. December 2009.
[11] G. J. Burke and A. J. Poggio.“Numerical Electromagnetic Code-2”. Ver. 5.7.5, Arie Voors, 1981
[12] M. C. T. Huynh. “A Numerical and Experimental Investigation of Planar Inverted-F Antennas
for Wireless Communication Applications”. M.Sc. Thesis, Virginia Polytechnic Institute and State
University, October 2000
[13] J.Yeo,Y.J.Lee, and R.Mittra, “ A novel dual-band WLAN antenna for Note book platforms,”
IEEE Antennas Propag Soc Int Symp Dig 2 (2004),1439-1442.

97
[14] S.J.Liao, K.L.Wong, and L.C.Chou, “Small-size uniplanar coupled-fed PIFA for 2.4/5.2/5.8
GHz WLAN operation in the laptop computer”,Microwave Opt Technol Lett 51(2009).
[15] K.L. Wong and L.C. Chou, “Internal cellular/WLAN combo antenna for laptop-computer
applications” ,Microwave Opt Technol Lett 47 (2005),402-406.
[16] C.H.Kuo ,K.L. Wong, and F.S. Chang, “Internal GSM/DCS dual-band open-loop antenna for
laptop application”, Microwave Opt Technol Lett 49(2007),680-684.
[17] X.Wang, W.Chen,and Z.Feng, ”Multiband antenna with parasitic branches for laptop
applications,” Electron Lett 43 (2007),1012-1013
[18] C.H.Chang and K.L.Wong, “Internal coupled-fed shorted monopole antenna for GSM
850/900/1800/1900/UMTS operation in the laptop computer”, IEEE Trans Antennas Propag 56
(2008),3600-3604.
[19] K.L. Wong and L.C.Lee,” Multiband printed monopole slot antenna for WlAN operation in the
laptop computer,”IEEE Trans Antennas Propag 57(2009).
[20] K.L.Wong, “Planar antennas for wireless communications,” Wiley, New York,2003.

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