Compact PIFA for 2.4 5 GHz dual ISM-band applications ...

Compact PIFA for 2.4=5 GHz dual ISM-band
applications
J.-I. Moon, D.-U. Sim and S.-O. Park
A compact and novel modified planar inverted-F antenna (PIFA) for
dual ISM-band application is proposed. The proposed antenna, including
a small ground plane, occupies a volume of 20 23.7 0.8 mm 3
(FR-4). The impedance bandwidth with 10 dB return loss is about
150 MHz (2380–2530 MHz) for 2.4 GHz band and 1450 MHz (5130–
6580 MHz) for 5 GHz band. The measured radiation patterns are
approximately omnidirectional and yield a gain of 1.0 dBi at
2440 MHz and 3.98 dBi at 5600 MHz, respectively.
Introduction: As portable wireless devices become smaller and have
the design requirements for multiband antennas, the antenna volume
including a ground substrate should be reduced. In particular, the
rapid development of the applications for wireless local area network
(WLAN) has promoted the novel antenna design mounted on a small
ground plane for dual ISM band, namely 2.4 GHz (2400–2483 MHz)
and 5 GHz (5150–5350=5725–5875 MHz), respectively. However, in
many previous papers [1, 2], the antenna performances are influenced
by the size of ground plane. Since the ground plane becomes a
primary source of radiation, the smaller ground strongly influences
small antenna properties. Therefore, when these antennas have a small
ground plane to apply to the practical applications, the performances
such as return loss, bandwidth and radiation gain at
the frequency of interest are typically reduced [3]. InthisLetter,a
compact PIFA model mounted on a small ground plane is proposed
and how bands can be tuned is described.
Antenna design: Fig. 1 shows the geometry of the proposed antenna
with the combination of the modified inverted-F patch and the
inverted L-shaped stub. The geometrical parameters of the length
and width of strip lines are optimised in an attempt to achieve design
goals at both the frequency bands of interest. For achieving the
resonant mode at 2.4 GHz band, the strip line starting from
the feeding point (point A) to the end point (point C) ischosento
be 31 mm corresponding to about a quarter of one wavelength. In
addition, to match the input impedance at 2.4 GHz frequency band
and contribute the radiating mode, the strip line (point B–point D) is
connected with the ground plane. The loop shape of the strip line
starting from point A to point D is a length of 24 mm. It is selected to
give a resonant frequency in the 5 GHz band. Both the z-directed
inverted L-shaped stub (height 6 mm, point E) and the ground plane,
which is implemented on the back side of the substrate, also play an
important role in enhancing the impedance bandwidth and the radiation
gain at both frequency bands.
z
y
x
1.8
23.7
15.5
C
3 2
Fig. 2 Measured and simulated return losses of PIFA shown in Fig. 1
20
2
5
B
1 D
2.6 A
7.5
5
a
50 W CPW
y
z
x
9
6
5
16.7
b
z
E
x
y
6
c
z
y
0.8
Fig. 3 Measured and simulated radiation patterns at 2440 MHz
2
x
E
6
— measured result
simulated result
a y-z plane (E y )
b x-z plane (E F )
c x-y plane (E F )
Fig. 1 Geometry of proposed antenna (unit: mm)
a Top view
b Bottom view
c Cross-sectional view
d Side view
d
Results: Fig. 2 shows the comparison results between the measured
and simulated return losses of the proposed antenna. The measurement
was performed using an Agilent 8722D network analyser and
the simulation result was obtained from an Ansoft HFSS. The return
losses shown in Fig. 2 illustrate the satisfactory bandwidth in both the
lower and upper resonant frequency bands of the proposed PIFA. The
measured and simulated radiation patterns for the designed antenna in
y-z, x-z, andx-y planes are shown in Figs. 3 and 4, respectively.
ELECTRONICS LETTERS 8th July 2004 Vol. 40 No. 14

As shown in Figs. 3 and 4, the radiation patterns are omnidirectional
and very similar to those of the y-directed dipole antenna. The
measured and simulated results agree well with each other at both
frequencies. The maximum measured andsimulatedradiationgainare
1.0 and 1.51 dBi at 2.44 GHz and 3.98 and 3.6 dBi at 5.6 GHz,
respectively.
Conclusions: A compact and novel planar inverted-F antenna (PIFA)
has been proposed and implemented. The proposed antenna exhibits
good impedance bandwidth as well as radiation performance despite
the miniaturised volume of 20 23.7 0.8 mm (FR-4). The obtained
performance of this antenna shows an attractive feature for 2.4=5 GHz
dual ISM-band applications.
Acknowledgment: This work was supported by the National Research
Laboratory (NRL) of the Ministry of Science and Technology, Korea,
under contract no. M1-0203-0015.
# IEE 2004 6 May 2004
Electronics Letters online no: 20045286
doi: 10.1049/el:20045286
J.-I. Moon, D.-U. Sim and S.-O. Park (School of Engineering,
Information and Communications University, Daejeon, Korea)
E-mail: jungick@icu.ac.kr
References
1 Lin, C.-C., Lee, G.-Y., and Wong, K.-L.: ‘Surface-mount dual-loop
antenna for 2.4=5 GHz WLAN operation’, Electron. Lett., 2003, 39,
(18), pp. 1302–1304
2 Moon, J.-I., and Park, S.-O.: ‘Small chip antenna for 2.4=5.8-GHz dual
ISM-band applications’, IEEE Antenna Wirel. Propag. Lett., 2003, 2,
(21), pp. 313–315
3 Huynh, M.-C., and Stutzman, W.: ‘Ground plane effects on planar
inverted-F antenna(PIFA) performance’, IEE Proc., Microw. Antennas
Propag., 2003, 150, (4), pp. 209–213
Fig. 4 Measured and simulated radiation patterns at 5600 MHz
— measured result
simulated result
a y-z plane (E y )
b x-z plane (E F )
c x-y plane (E F )
ELECTRONICS LETTERS 8th July 2004 Vol. 40 No. 14