608 PIERS Proceedings, Moscow, Russia, August 19–23, 2012
A Simple Miniaturized Triple-band Antenna for WLAN/WiMAX
H. M. El Misilmani,M. Al-Husseini,K. Y. Kabalan,and A. El-Hajj
ECE Department, American University of Beirut, Beirut 1107 2020, Lebanon
Abstract—The design of a simple small-size multi-band antenna for wireless local area net-
work (WLAN) and worldwide interoperability for microwave access (WiMAX) application is
presented in this paper. The antenna covers the 2.4/5.2/5.8-GHz WLAN operating bands and
the 2.5/3.5/5.5-GHz WiMAX bands. The proposed printed-type antenna is based on a 1.6 mm-
thick FR4 epoxy substrate with dimensions 25 mm ×38 mm. It has a rectangular split-ring slot
enclosed inside a rectangular patch. The inclusion of the split-ring slot and the U-shaped slot in
the partial ground plane gives resonance at two additional frequencies. The dimensions of the
patch, the ground, and the two slots are optimized to obtain these desired functional frequency
Due to the rapid and wide development of wireless communications, the design goal is heading
towards the desired features of compact, lightweight, multi-band and low cost antennas. UWB
antennas have the advantage of covering a very wide frequency range. In , a UWB antenna
operational over the 2–11 GHz range is presented. However, UWB antennas are prone to noise from
unwanted frequencies, which could degrade the original message. On the other hand, reconﬁgurable
antennas are designed to be able to control the resonance of the antenna and limit the disadvantage
of UWB antennas. A frequency reconﬁgurable antenna is proposed in . Though very robust,
reconﬁgurable antennas are complex as they require the use of switching elements and their biasing
lines, or other complicated reconﬁguration mechanisms. Multi-band antennas can be thought of as
an intermediate solution combining simplicity and multi-frequency operation.
The advantage of the multi-band antennas is to be able to integrate several frequency bands
on one single antenna, making it useful for several frequency ranges. These multi-band antennas
could contain frequency ranges from several wireless applications. [3, 4] represent two antennas
working on multi-frequency bands. In this paper, the antenna presented is capable of working on
triple-frequency bands, for the two diﬀerent applications, WLAN and WiMAX.
In [5–18] several printed antenna designs for both WLAN and WiMAX applications have been
presented. In [5–7], the triple-band characteristic is designed by etching two narrow slots with
diﬀerent lengths on a wideband monopole antenna. In , the design uses a trapezoidal ground
to achieve the triple-band frequencies of WLAN/WiMAX applications. In , a triple-band unidi-
rectional coplanar antenna is presented, but with a large size of 100 ×60 mm2. Usually, to meet
the requirements of mutli-band frequency range, a various types of conﬁgurations could be used.
In , a meander T-shape with a long and a short arm are used to achieve multi-band frequency.
A multifractal structure is used in . In [12, 13], a ﬂared shape with V-sleeve or Y-shape is
implemented to realize the multi-band operation. However these antennas have a large size com-
paring to the limited space of mobile wireless terminals. Through the development of antenna
design, slot structures have been proposed to reduce the size of the multi-band antennas. In ,
the use of U-slots with a combination with an L-probe feed is used to produce dual and multi-
band characteristics. A triangular-slot loaded multi-band antenna excited by the strip monopole is
presented in . In , the adjustment of the size of the slots on the radiating patch improves
the performance of the coplanar waveguide-fed monopole antenna, but with a low antenna gain.
Meandering slot antennas, in [17, 18], could also be used as well with diﬀerent slots to generate two
resonant modes. However, the complex structures of these antennas make them unsuitable for the
practical applications. In  a miniaturized multi-frequency antenna is proposed using circular
ring, a Y-shape-like strip, and a defected ground plane.
In this paper, using a split-ring slot enclosed inside a rectangular patch and etching a U-shaped
slot in the partial ground plane are the two techniques used to achieve not only triple-band operation
performance, but also smaller size and simpler structure. By using the three diﬀerent resonant
frequencies, the proposed antenna can generate three resonant modes to cover three desired bands
for WLAN and WiMAX applications. The geometry and the design guidelines of the proposed
Progress In Electromagnetics Research Symposium Proceedings, Moscow, Russia, August 19–23, 2012 609
antenna structures are presented in Section 2. Experimental results are presented in Section 3. In
Section 4 a brief conclusion is given.
2. ANTENNA STRUCTURE AND DESIGN
The conﬁguration of the proposed triple-band antenna is shown in Figures 1(a)–(b). The rectan-
gular patch is the main radiating element of the antenna combined with split-ring slot enclosed
inside of it. The proposed printed-type antenna is based on a 1.6 mm-thick FR4 epoxy substrate
with dimensions 25 mm ×38 mm, fed by a 50Ω microstrip feed line with a width of 3 mm and a
length of 12.06 mm. The partial ground plane is located on the backside of the dielectric substrate,
shown in Figure 1(b), where a U-shaped slot is illustrated.
Figures 2(a)–(d) and Figure 3 represent the design evolution of the proposed antenna and its
corresponding simulated reﬂection coeﬃcient. Initially, the antenna in Figure 2(a) consists of a
rectangular patch in addition to a partial rectangular ground. As shown in Figure 3(a), there is
one operating band from 3 to 5 GHz. The inclusion of the split-ring slot, Figure 2(b), leads to
the excitation of an additional coverage of the 2.4–2.5GHz band, shown in Figure 3(b), without
increasing the size, where the current will be divided between the rectangular patch and the split-
Figure 1: Geometry of the proposed antenna. (a) Front view, (b) back view.
(a) (b) (c) (d)
Figure 2: (a)–(d) The evolution of the antenna de-
Figure 3: Simulated reﬂection coeﬃcient of each de-
Figure 4: The fabricated antenna. (a) Font view, (b) back view.
610 PIERS Proceedings, Moscow, Russia, August 19–23, 2012
ring slot giving two resonance frequencies. In Figure 2(c) and under the 50 Ω microstrip feed line,
the ground plane is defected by etching a U-shaped slot without adding a split-ring slot in the
rectangular patch. The U-shaped slot, as shown in Figure 3(c), gives resonance in the 3–4 and 5.2–
5.9 GHz bands. Finally, in Figure 2(d), the two slots were added to the design to achieve resonance
in the three frequency bands, 2.4–2.5, 3–4, 5.2–5.9 GHz, as shown in Figure 3(d). The dimensions of
the patch, the ground, and the two slots are optimized to obtain these desired functional frequency
ranges using Ansoft HFSS.
Figures 4(a)–(b) show the fabricated antenna, with the dimensions shown in Table 1 for both
upper and lower part.
3. RESULTS AND DISCUSSION
The computed and measured reﬂection coeﬃcient plots are given in Figure 5, where good analogy
From the measured results it is seen that the antenna covers three frequency bands, 2.4–2.5,
3–4, and 5.4–5.9 GHz bands, making it suitable for WLAN operating in the 2.4, 5.2 and 5.8 GHz
bands, and WiMAX networks operating in the 2.5, 3.5 and 5.5 GHz bands.
Due to its geometry as a printed monopole, and the use of the partial ground plane, the antenna
has omnidirectional radiation patterns, as shown in Figure 6 for the 2.4, 3.5, and 5.8 GHz frequen-
Table 1: The antenna dimensions (in mm).
Parameter Size (mm) Parameter Size (mm) Parameter Size (mm)
W25 W s 12 Lg 9
L38 Ls 12.10 W u 7.5
W f 3Ds 2.10 Lu 3
Lf 12.06 Lsr 7.9 Du 2.5
W r 18 W f s 0.9 Dg 5.5
Lr 21 Sd 4.4 Su 1
Figure 5: Simulated (dashed line) and measured (solid line) reﬂection coeﬃcient.
(a) (b) (c)
Figure 6: The antenna gain computed at (a) 2.4, (b) 3.5 and (c) 5.5 GHz in the XZ plane (H-plane) and
Y Z plane (E-plane).
Progress In Electromagnetics Research Symposium Proceedings, Moscow, Russia, August 19–23, 2012 611
Table 2: Simulated antenna gain at the frequencies of operation.
Frequency (GHz) Gain (dB) Frequency (GHz) Gain (dB)
2.40 1.8811 4.00 2.0398
2.45 1.7991 5.20 2.0568
2.50 1.6529 5.50 1.8904
3.00 1.7120 5.80 1.3232
3.50 1.8529 5.90 1.4112
cies. These simulated patterns reveal an equal gain in the XZ plane (H-plane), and a pattern with
the shape of digit 8 in the Y Z plane (E-plane).
The antenna gain computed at 2.4–2.5, 3–4, 5.2–5.9 GHz is given in Table 2. As shown, the gain
of the proposed antenna within the operating bands satisﬁes the requirement of several wireless
A novel triple-band antenna suitable for WLAN/WiMAX applications is proposed in this paper.
Using a split-ring slot implanted in the rectangular patch and a U-shaped slot etched partial ground
plane, three resonant modes with excellent impedance performance are achieved.
The compact size, triple-band frequency, excellent radiation patterns, good gain and a simple
structure makes this antenna suitable for practical wireless communication systems, working on
WLAN and WiMAX networks, in three diﬀerent frequency bands, 2.4–2.5, 3–4, 5.2–5.9 GHz.
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