A Novel Integrated Dual-Band Antenna for all Relevant
Wireless-LAN Standards (IEEE 802.11a, b and g)
A. Rennings, R. Müller, S. Otto, P. Waldow, and I. Wolff
EE Department (ATE), Duisburg-Essen University, Bismarckstr. 81, 47048 Duisburg, Germany,
Tel: +49-203-379-3183, Fax: +49-203-379-3499, E-mail: renny@ate.uni-duisburg.de
Abstract — A novel dual-band antenna that can be used
for all relevant Wireless-LAN standards, IEEE 802.11a, b,
and g, is presented. The proposed antenna is compact, costeffectively and precisely to manufacture, with an omnidirectional pattern and a sufficient bandwidth for all of the
above mentioned WLAN standards. This printed antenna
might be a choice for nowadays or future multi-band, multimode WLAN applications. The performance was simulated
using commercial FDTD tools, and validated with
measurements on fabricated prototypes.
I. INTRODUCTION
Wireless local area networks (WLANs) are becoming
increasingly popular, since they provide high speed
connectivity and easy access to networks without
requiring wiring. Most of the current WLAN products
being deployed are based on the IEEE 802.11b standard
operating at 2.4 GHz with data delivery rates of up to 11
Mbps. The IEEE 802.11a standard is for WLAN devices
in the 5 GHz band operating up to data rates of 54 Mbps.
This standard provides more bandwidth and channels than
the first one. Additionally, the 5 GHz spectrum has less of
the interference that plagues the lower frequency band,
since microwave ovens, portable phones or Bluetooth
devices operate also in the 2.4 GHz ISM band. The new
IEEE 802.11g standard is being developed to offer 22
Mbps up to 54 Mbps data rates at 2.4 GHz using the socalled orthogonal frequency division multiplex (OFDM)
modulation. There are already multi-band, multi-mode
WLAN cards available on the market, i.e., no matter
where it operates, the WLAN product identifies the
standard used at that location and switches to the
appropriate mode, IEEE 802.11a, b or g. For the above
mentioned reasons there should be a demand for multiband antennas enabling radiation in the frequency bands
of the IEEE 802.11a, b and g standards. In [1] and [2]
multi-band versions of the planar inverted-F antenna
(PIFA) have been published. To the best knowledge of the
authors there has been no paper published on a multi-band
version of the so-called integrated inverted-F antenna – a
printed antenna. An antenna printed on a substrate has
some advantages compared to other antennas, like the
PIFA: It is usually cheaper and more precisely to
manufacture. Furthermore, the multi-band antenna
presented in this paper has the advantage to have a very
low profile with no additional height above the substrate.
II. BASIC DESIGN CONSIDERATIONS FOR THE NOVEL
DUAL-BAND ANTENNA
In this section the development of the multi-band
antenna is outlined. Starting point was an ordinary
integrated inverted-F antenna (I-IFA) as presented in [3].
Our new antenna concept is based on a modified I-IFA
that is even more compact than the ordinary one. Because
of its shape, depicted in Fig. 1, this antenna is named
integrated folded-h antenna (I-FhA). Two of these foldedh antennas have been connected as depicted in Fig. 2 to
form a multi-resonant structure.
≈
≈
Via
Ground Plane
Fig. 1: Top view of the integrated folded-h antenna (I-FhA)
Via
Feed
Via
Fig. 2: Fusion of two folded h-antennas for multi-band operation
III. FDTD-SIMULATIONS AND MEASUREMENTS OF
PROTOTYPES PRINTED ON A PCMCIA CARD
With the basic considerations of section II as a first
design the 3D FDTD field simulator EMPIRE™ [4] and
CST MICROWAVE STUDIO™ [5] have been used to
simulate and optimize the proposed antenna. During that
optimization it turned out that the antenna structure
depicted in Fig. 3 (dimensions in mm) fulfills the dualband requirements the best. The L-shaped connector to the
ground plane on the left hand side was sufficient for the
design, therefore the other one on the right hand side (see
Fig. 2) has been removed. Since a possible application of
the proposed antenna is the integration into a multi-band,
multi-mode WLAN PCMCIA card, such a PCMCIA
board is used as carrier for the antenna. Its dimensions are
approx. 50 mm x 100 mm. The substrate parameters were
RT/duroid 5870 with an εr of 2.33 and a thickness of 508
µm (20 mil).
50
25
8
5
y Via
≈
≈
For the 2.4 GHz ISM band (2.4 to 2.4835 GHz) the
antenna has a sufficient bandwidth of approx. 100 MHz at
10dB. The IEEE 802.11a standard is using three subbands
within the 5 GHz ISM band. The first subband is from
5.15 to 5.25 GHz and it allows up to 16 dBm transmitting
RF power. The second one is from 5.25 to 5.35 GHz with
23 dBm maximum power, and the third one, mainly
intended for outdoor applications, is from 5.725 to 5.825
GHz with 29 dBm max. power. In these subbands the
antenna has an excellent return loss below 15dB. Because
of the additional notch between 5.5 and 6.0 GHz, one
might call it a triple-band antenna. Altogether it has a
bandwidth of 1.3 GHz (from 4.8 to 6.1 GHz) or 23% at
10dB. Some prototypes of the antenna have been
fabricated to validate the simulations with measured data.
In Fig. 5/6 one of the prototypes printed on RT/duroid
5870, representing the PCMCIA card, is shown.
100
x
z
Ground Plane
Fig. 3: Top view of the antenna with dimensions in mm
The SMA connector was modeled by using a short
coaxial line within the EMPIRE simulation. For the six
boundaries PMLs have been used to emulate the free
space condition. The simulated and measured return loss
in dB of the proposed antenna is shown in Fig. 4. The
difference between the EMPIRE result and the
measurement in the frequency range from 5 to 6 GHz
might be caused by an non-accurate modeling of the
SMA-to-microstrip line transition. The S11-measurement
has been carried out with the HP NWA 8722C.
0
Fig. 6: Top view of the fabricated antenna printed on RT/duroid
-5
A possible application as an antenna for a dual-standard
Wireless-LAN PCMCIA card “inside” a laptop computer
is shown in Fig. 7.
-10
S11 [dB]
Fig. 5: Photo of one of the fabricated prototypes
-15
-20
-25
EMPIRE
Measurement
CST
-30
-35
2
2,5
3
3,5
4
4,5
5
5,5
6
6,5
7
Frequency [GHz]
Fig. 4: Simulated and measured return loss of dual-band antenna
Fig. 7: One possible application for the proposed antenna
In Fig. 8 to 10 the magnitude of the current density on the
antenna is depicted at 2.45, 5.3 and 5.8 GHz. The field
plots give a very good inside which part of the antenna is
resonant at a certain frequency.
antenna should operate in that direction to minimize
radiation into the human body.
0
340
350
10
5
330
20
30
0
320
40
-5
-10
310
50
-15
300
60
-20
290
70
-25
-30
280
80
-35
270
90
-40
260
100
250
110
240
120
230
130
220
Fig. 8: Simulated current density |J(x,y,h)| @ 2.45 GHz
140
210
150
200
190
170
160
180
Ephi@2.45GHz
Etheta@2.45GHz
Ephi@5.5GHz
Etheta@5.5GHz
Fig. 11: Directivity pattern of |Eϕ| and |Eθ| in dBi @ 2.45 and 5.5 GHz,
(xy-cut, θ = 90°)
0
340
350
10
5
330
20
30
0
320
40
-5
-10
310
50
-15
300
60
-20
Fig. 9: Simulated current density |J(x,y,h)| @ 5.3 GHz
290
70
-25
-30
280
80
-35
-40
270
90
260
100
250
110
240
120
230
130
220
140
210
150
200
190
170
160
180
Fig. 10: Simulated current density |J(x,y,h)| @ 5.8 GHz
Another important issue is the radiation pattern. Fig. 9 to
11 illustrate the with EMPIRE simulated directivity
pattern of the dual-band antenna at 2.45 GHz - the center
frequency in the lower ISM band - and at 5.5 GHz in the
middle of the three subbands of the 802.11a standard. In
the xy-cut the radiation pattern is nearly omni-directional
for both frequencies – except in the direction of the
ground plane at ϕ = 270°. There is a notch, since the
ground plane acts as reflector. A user in the vicinity of the
Ephi@2.45GHz
Etheta@2.45GHz
Ephi@5.5GHz
Etheta@5.5GHz
Fig. 12: Directivity pattern of |Eϕ|and |Eθ| in dBi @ 2.45 and 5.5 GHz,
(yz-cut, ϕ = 0°)
To give the reader a three-dimensional impression of the
quasi omni-directional pattern, the simulated 3D
directivity pattern (total polarization) is depicted for two
different frequencies at 2.45 and 5.5 GHz in Fig. 14/15. It
has been simulated with the CST tool. The notch in the
direction of the ground plane is located at the bottom side
of the pattern and can therefore not be seen.
0
340
350
330
10
5
20
30
0
320
40
-5
-10
310
50
-15
300
60
-20
290
70
-25
-30
280
80
-35
-40
270
90
260
100
250
110
240
120
230
130
220
140
210
150
200
190
170
160
Another important issue - especially for the 802.11b
networks, since it uses direct sequence spread spectrum
(DSSS) modulation with a relatively wide channel, nearly
30 MHz - is the multi-path propagation. This bandwidth
leaves enough room for lower frequency elements of the
DSSS signal to reflect off obstacles much different than
the higher frequency elements of the signal. To overcome
problems caused by multi-path propagation one can use
two antennas with a different orientation for each radio in
order to increase the odds of receiving a better signal on
either of the antennas. Future research will focus on that
topic. The standards 802.11a and 802.11g use the OFDM
modulation, where the information is transmitted on many
narrow sub-channels. Therefore the impact of multi-path
propagation is reduced.
180
Ephi@2.45GHz
Etheta@2.45GHz
Ephi@5.5GHz
Etheta@5.5GHz
Fig. 13: Directivity pattern of |Eϕ|and |Eθ| in dBi @ 2.45 and 5.5 GHz,
(yz-cut, ϕ = 90°)
IV. CONCLUSION
In this paper, an integrated antenna with multi-band
properties, printed on a PCMCIA card, was presented.
This design is compact, cost-effectively and precisely to
manufacture, and has an omni-directional pattern with
sufficient bandwidth for all relevant WLAN standards,
IEEE 802.11a, b, g. The presented antenna might be a
candidate for nowadays or future multi-band, multi-mode
WLAN applications.
REFERENCES
Fig. 14: 3D directivity pattern in dBi @ 2.45 GHz
Fig. 15: 3D directivity pattern in dBi @ 5.5 GHz
[1] Z. D. Liu, P. S. Hall, and D. Wake, "Dual-frequency planar
inverted-F antenna," IEEE Trans. Antennas and
Propagation, vol. 45, no. 10, pp. 1451-1458, 1997.
[2] M.-S. Tong, M. Yang, Y. Cheng, and R. Mittra, "Finitedifference time-domain analysis of a stacked dualfrequency microstrip planar inverted-F antenna for mobile
telephone handsets," IEEE Trans. Antennas and
Propagation, vol. 49, no. 3, pp. 367-376, 2001.
[3] M. Ali and G. Hayes, "Analysis of integrated inverted-F
antennas for Bluetooth applications," 2000 IEEE AP-S
Conference on Antennas and Propagation for Wireless
Communication, Massachusetts, pp. 21-24, Nov. 2000.
[4] IMST GmbH, “User manual for the 3D EM time domain
simulator Empire”, www.empire.de/empire.pdf, June 2002.
[5] CST GmbH, “User manual for CST MICROWAVE
STUDIO”.