A low-cost, one-piece, flat-plate dipole antenna for dual WLAN band operation is presented. The dipole antenna is rectangular in shape with the dimensions 10 mm × 37 mm and fed by 50-ohm mini-coaxial cable. By cutting two L-shaped slits in each radiating arm, two dipole arms are obtained, which form a larger dipole and a smaller dipole antennas for the 2.4 and 5 GHz band operation respectively. The dipole arms are further short-circuited, making it possible for the antenna to be fabricated by stamping a single, flat metal plate only. The impedance bandwidth for 2.4/5 GHz WLAN operation is with VSWR below 1.5 and good omnidirectional radiation patterns are also observed.

1. LOW-COST FLAT METAL-PLATE
DIPOLE ANTENNA FOR 2.4/5-GHZ
WLAN OPERATION
Saou-Wen Su and Jui-Hung Chou
Technology Research Development Center, Lite-On Technology
Corporation, Taipei 11492, Taiwan; Corresponding author:
susw@ms96.url.com.tw
Received 2 November 2007
ABSTRACT: A low-cost, one-piece, flat-plate dipole antenna for dual
WLAN band operation is presented. The dipole antenna is rectangular
in shape with the dimensions 10 mm 37 mm and fed by 50- mini-
coaxial cable. By cutting two L-shaped slits in each radiating arm, two
dipole arms are obtained, which form a larger dipole and a smaller
dipole antennas for the 2.4- and 5-GHz band operation, respectively. The
dipole arms are further short-circuited, making it possible for the antenna
to be fabricated by stamping a single, flat metal plate only. The impedance
bandwidth for 2.4/5-GHz WLAN operation is with VSWR below 1.5 and
good omnidirectional radiation patterns are also observed. © 2008 Wiley
Periodicals, Inc. Microwave Opt Technol Lett 50: 1686 –1687, 2008;
Published online in Wiley InterScience (www.interscience.wiley.com).
DOI 10.1002/mop.23461
Key words: antennas; planar antennas; dipole antennas; metal-plate
antennas; WLAN antennas
1. INTRODUCTION
Coaxial-line-fed, mobile-unit antennas of a small form factor [1-7]
are very attractive to WLAN applications in many sorts of wireless
electronics devices such as laptops and audio/video adapters. Most
of them are in the form of printed antenna structures [1-5] in either
monopole [1-3] or dipole antenna [4, 5] designs. As to metal-plate
structures, Planar inverted-F Antennas (PIFAs) [6, 7] are com-
monly utilized in industry as standard antenna solutions. More-
over, small mobile-unit antennas in metal-plate structures have
better antenna gain and radiation efficiency, and also less costly
than printed antennas. However, in general, these kinds of mobile-
unit, metal-plate PIFAs cannot provide good omnidirectional ra-
diation patterns compared with dipole antennas.
In this letter, we demonstrate a one-piece, flat, metal-plate
dipole antenna for dual-band WLAN operation in the 2.4-GHz Figure 1 (a) Geometry of the proposed low-cost flat metal-plate dipole
(2400 –2484 MHz) and 5-GHz [5.2 GHz (5150 –5350)/5.8 GHz antenna. (b) Photograph of a working sample fed by a 50- mini-coaxial
(5725–5825 MHz)] bands. The proposed antenna retains the merit cable. [Color figure can be viewed in the online issue, which is available at
of the aforementioned, mobile-unit, flat-plate PIFAs and yet has www.interscience.wiley.com]
better omnidirectional radiation characteristics. The antenna com-
prises two radiating arms and a shorting strip, short-circuiting both
radiating arms, which form a one-piece, flat, metal-plate structure.
Two L-shaped slits, in the opposite direction, are further cut in stamping a one-piece, flat metal plate at low cost. Photograph of a
each of the two radiating arms to achieve two separate resonant working sample, made of a 0.3-mm-thick copper–nickel–zinc al-
paths for dual band operation. The proposed antenna is very suited loy, is shown in Figure 1(b).
to be installed within the housing of wireless electronics devices In the proposed design, two L-shaped slits, in the opposite
and ideal for integration into WLAN applications. direction, are cut in each radiating arm [detailed dimensions are
given in Fig. 1(a)]. When there are no L-shaped slits, the two
2. ANTENNA DESIGN radiating arms form a simple, planar dipole antenna, operating at
Figure 1(a) shows the configuration of the proposed antenna. The about 3.15 GHz. With the presence of the L-shaped slits, two new
antenna comprises two radiating arms and a narrow shorting strip dipole arms are obtained, which form a larger dipole and a smaller
that connects both radiating arms. The antenna is rectangular in dipole antennas for operation in the 2.4- and 5-GHz bands, respec-
shape with the dimensions 10 mm 37 mm and fed by 50- tively. Note that the distance (d) between the points A, B, and the
mini-coaxial cable, with central conductor connected to the point shorting strip has a major effect on the impedance matching, which
A and the outer sheath soldered to the point B. The points A and is adjusted to control the inductive reactance to compensate for
B can be designated vice versa because of the dipole antenna capacitive coupling between the two radiating arms. The near
symmetrical in shape. The antenna can easily be constructed from optimal value of the distance (d), in this case, is 1 mm.
1686 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 6, June 2008 DOI 10.1002/mop

2. Figure 4 Measured peak antenna gain and measured radiation effi-
ciency. [Color figure can be viewed in the online issue, which is available
Figure 2 Measured return loss for the proposed antenna; d 1 mm. at www.interscience.wiley.com]
[Color figure can be viewed in the online issue, which is available at
www.interscience.wiley.com]
4. CONCLUSION
3. RESULTS AND DISCUSSION
A novel, flat, metal-plate dipole antenna capable of providing
Figure 2 shows the measured return loss of a design prototype. For dual-band operation in the 2.4- and 5-GHz WLAN bands has been
frequencies over the 2.4- and 5-GHz WLAN bands, the measured proposed. The antenna with a one-piece, metal-plate structure is
impedance matching is all better than 10 dB, even better than 14 easy to implement and can be a promising solution for keeping the
dB (about 1.5:1 VSWR), which meets the bandwidth specification
cost down. The dual operating bands can easily be controlled by
for 2.4/5-GHz WLAN operation easily. Figure 3 plots the far-field,
the larger dipole and the smaller dipole arms obtained by cutting
3D radiation patterns at 2442, 5250, and 5775 MHz, measured at
the L-shaped slits in the proposed design. Good radiation charac-
the 3 3 7-m3 anechoic chamber at Lite-On Technology Corp.,
teristics of the proposed antenna have been also observed.
Taipei. Across the operating bandwidth are observed good, omni-
directional radiation patterns in the x–z plane, similar to the con-
ventional, wire-dipole radiation characteristics. Note that the om-
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© 2008 Wiley Periodicals, Inc.
Figure 3 Measured 3D radiation patterns at 2442, 5250, and 5775 MHz.
[Color figure can be viewed in the online issue, which is available at
www.interscience.wiley.com]
DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 6, June 2008 1687