Two promising, internal, shorted monopole antennas for 700 MHz and WLAN/WiMAX operation are combined in an arrangement with minimized mutual coupling for palm-sized mobile applications. The two stamped, metal-plate antennas with a 2 mm gap therein between can be integrated into a compact configuration and are then mounted near one side of the system circuit board. With the suitable shorting locations and arrangement of the two antennas, good isolation (S21 < –20 dB) between the two ports can easily be obtained. Analysis of placing a CCD shielding cylinder between the two antennas and the two shorting strips joined to form a shorting wall are also conducted. Detailed designs of the two antennas are described, and the results thereof are discussed.

1. internet device (MID) or ultramobile PC (UMPC) [4]. The two
INTEGRATION OF INTERNAL 700 MHz antennas are easily constructed by stamping a flat, metal plate
AND WLAN/WiMAX ANTENNAS FOR shown in Figure 1(b), in which the detailed dimensions are also
PALM-SIZED MOBILE DEVICES given. Both of the antennas are short-circuited to a small ground
(10 10 mm2) protruding from the main system ground, and the
Jui-Hung Chou and Saou-Wen Su
Technology Research Development Center, Lite-On Technology small ground is useful for hosting a shielding can of some compact
Corporation, Taipei 114, Taiwan; Corresponding author: electronic component such as a charge-coupled device (CCD).
susw@ms96.url.com.tw Notice that the shorting strips of the two antennas is located facing
each other (with a 2-mm gap), which contributes to better shielding
Received 1 March 2008 effect between the antennas and, in turn, leads to good isolation
[5].
ABSTRACT: Two promising, internal, shorted monopole antennas for For the 700-MHz antenna, a meandered structure to increase
700 MHz and WLAN/WiMAX operation are combined in an arrange- the resonant path of excited surface currents and at the same time
ment with minimized mutual coupling for palm-sized mobile applica- to retain a compact configuration is utilized. This quarter-wave-
tions. The two stamped, metal-plate antennas with a 2-mm gap therein length resonant structure controls a fundamental resonant mode for
between can be integrated into a compact configuration and are then 700 MHz operation at about 752 MHz. As for the WLAN/WiMAX
mounted near one side of the system circuit board. With the suitable antenna, a patch-like plate (20 10 mm2) with a 6-mm long slit
shorting locations and arrangement of the two antennas, good isolation
(S21 20 dB) between the two ports can easily be obtained. Analysis
of placing a CCD shielding cylinder between the two antennas and the
two shorting strips joined to form a shorting wall are also conducted.
Detailed designs of the two antennas are described, and the results
thereof are discussed. © 2008 Wiley Periodicals, Inc. Microwave Opt
Technol Lett 50: 2948 –2951, 2008; Published online in Wiley Inter-
Science (www.interscience.wiley.com). DOI 10.1002/mop.23833
Key words: antennas; mobile antennas; monopole antennas; 700-MHz
antennas; WLAN antennas; WiMAX antennas
1. INTRODUCTION (a)
Very recently, with the DTV transition, the 700-MHz band (698 –
806 MHz), which had been previously occupied by TV broadcast-
ers in Channels 52– 69, are reclaimed for the usage of commercial
and public safety service [1]. Beginning on January 24, 2008, the
700-MHz band has been put up for auction, held by Federal
Communications Commission (FCC), to facilitate the establish-
ment of an interoperable communications network [2]. It can be
foreseen that the development of public wireless infrastructure, in
which the consumer will be able to use a great variety of services,
will be triggered. In addition, in conjunction with the WLAN and
WiMAX technologies, features such as wireless access to the
internet and multimedia video/audio telephony, can be built into
the mobile device as added incentives for the consumer to use
these devices. To make the concept possible, we present in this
article a new design for the integration of a 700 MHz and a
WLAN/WiMAX internal antenna for palm-sized mobile devices.
The two proposed, mobile antennas are capable of operating in the
700 MHz band, and the 2.4-GHz (2400 –2484 MHz) WLAN band
and the 2.5-GHz (2495–2690 MHz) WiMAX band [3], respec-
tively. The antennas are suited to be mounted and integrated near
one side of the system circuit board. By arranging the two antennas
with their shorting strips facing each other, good isolation over the
operating bands is achieved. The incorporation of the 700-MHz
and the WLAN/WiMAX antennas into the mobile device enables
the user to have seamless access to wireless network. The design
of the prototype is elaborated, and the experimental and simulation
results are presented.
2. DESIGN CONSIDERATIONS OF TWO INTERNAL (b)
MONOPOLES
Figure 1(a) shows the proposed, integrated 700 MHz and WLAN/ Figure 1 (a) The proposed, internal, 700-MHz and WLAN/WiMAX
WiMAX monopole antennas near one side of the system circuit monopole antennas integrated in palm-sized mobile devices. (b) Detailed
board and concealed inside a palm-sized mobile device. The size dimensions of the 700-MHz and WLAN/WiMAX antennas unbent into a
of the ground plane (120 80 mm2) can be considered the one flat, metal-plate structure [Color figure can be viewed in the online issue,
with a 6- to 7-inch screen for practical applications in mobile which is available at www.interscience.wiley.com]
2948 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 11, November 2008 DOI 10.1002/mop

2. Figure 2 The photo of the antenna working samples made of a 0.3-mm
thick alloy [Color figure can be viewed in the online issue, which is
available at www.interscience.wiley.com]
Figure 4 Measured 3D radiation patterns at 752 MHz for the 700 MHz
antenna studied in Figure 3 [Color figure can be viewed in the online issue,
which is available at www.interscience.wiley.com]
(width 2 mm) for lowering the operating frequency is utilized. This
patch-like monopole antenna is also operated as a quarter-wave-
length resonant structure, and in general, both the length and the 3. RESULTS AND DISCUSSION
width of the plate determine the center frequency about 2545 MHz Figures 3(a) and 3(b) show the measured and simulated reflection
of the resonant mode for 2.4-GHz WLAN/2.5-GHz WiMAX op- coefficient (S11 for the 700 MHz antenna, S22 for the WLAN/
eration. WiMAX antenna) and isolation (S21). It is first noticed that, in
general, the experimental data compare favorably with the simu-
lation results, which are based on the finite element method. The
impedance matching for frequencies across the 700-MHz band, the
2.4-GHz WLAN band, and the 2.5-GHz WiMAX band is all less
than 6 dB (3:1 VSWR) and even well below 10 dB in both the
WLAN and WiMAX bands. The isolation between the two anten-
nas remains less than about 20 and 30dB over the 700-MHz
band and the WLAN/WiMAX band, respectively. Notice that the
second resonant mode of the 700-MHz antenna is found at about
1.45 GHz. That is, the frequency ratio of the antenna upper to
lower resonant mode is close to 2, which is largely due to the
effects of the meandered structure in the 700-MHz antenna.
Figures 4– 6 give the measured radiation patterns at 752, 2442,
and 2593 MHz. The far-field 3D radiation patterns were measured
at a fully anechoic chamber (dimensions 3 3 7 m3) at Lite-On
Technology. The 3D measurement system uses the great-circle
method and is equipped with a dual-polarized horn as a receiving
(a) antenna. The radiation characteristics for the 700-MHz antenna
resemble those of the mobile-phone antenna for GSM operation, in
(b)
Figure 3 Reflection coefficients (S11 for the 700 MHz antenna, S22 for
the WLAN/WiMAX antenna) and isolation (S21) between the two anten- Figure 5 Measured 3D radiation patterns at 2442 MHz for the WLAN/
nas: (a) measured results; (b) simulated results [Color figure can be viewed WiMAX antenna studied in Figure 3. [Color figure can be viewed in the
in the online issue, which is available at www.interscience.wiley.com] online issue, which is available at www.interscience.wiley.com]
DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 11, November 2008 2949

3. is seen to be in the direction of the system ground plane ( x
direction here), which behavior shows no particular distinction
between the proposed and other small 2.4-GHz antennas for PDA
phone applications [10 –13]. Figures 7(a) and 7(b) present the
measured peak antenna gain and radiation efficiency for 700 MHz
and 2.4-GHz WLAN/2.5-GHz WiMAX operation. In the 700-
MHz band, the peak gain is in the range of 1.5–2.6 dBi with the
radiation efficiency above 64%. As for the WLAN/WiMAX bands,
Figure 6 Measured 3D radiation patterns at 2593 MHz for the WLAN/
WiMAX antenna studied in Figure 3 [Color figure can be viewed in the
online issue, which is available at www.interscience.wiley.com]
which dipole-like radiation is obtained with omnidirectional pat-
tern in the plane (the y–z plane in this study and two nulls in the
x axis direction) perpendicular to the ground plane at the longer
side [6 –9]. Also, no major difference is observed for radiation
patterns at 2442 and 2593 MHz, which suggests stable radiation
properties for the WLAN/WiMAX antenna. In addition, the max-
imum radiation over the 2.4-GHz WLAN/2.5-GHz WiMAX bands
(a)
(a)
(b) (b)
Figure 7 Measured peak antenna gain and radiation efficiency for the Figure 8 Simulated reflection coefficients (S11, S22) and isolation (S21)
two antennas studied in Figure 3: (a) for the 700 MHz antenna; (b) for the for the case with (a) a common shorting wall and (b) a CCD shielding
WLAN/WiMAX antenna [Color figure can be viewed in the online issue, cylinder [Color figure can be viewed in the online issue, which is available
which is available at www.interscience.wiley.com] at www.interscience.wiley.com]
2950 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 11, November 2008 DOI 10.1002/mop

4. the peak antenna gain is between 3.9 and 5.1 dBi, and the radiation 8. C.Y. Chiu, P.L. Teng, and K.L. Wong, Shorted, folded planar mono-
efficiency exceeds about 72%. The radiation efficiency was ob- pole antenna for dual-band mobile phone, Electron Lett 39 (2003),
tained in the 3D test system (software) by calculating the total 1301–1302.
radiated power of the antenna under test over the 3D spherical 9. K.L. Wong, Y.C. Lin, and T.C. Tseng, Thin internal GSM/DCS patch
antenna for a portable mobile terminal, IEEE Trans Antennas Propagat
radiation and then dividing the sum by the input power (default
54 (2006), 238 –243.
value of 0 dBm here).
10. S.W. Su, T.Y. Wu, Y.T. Cheng, and K.L. Wong, A foam-base surface-
To move on further practical antenna applications, the two mountable shorted monopole antenna for WLAN application, Micro-
proposed antennas were combined to form a single antenna ele- wave Opt Technol Lett 38 (2003), 501–503.
ment by connecting both shorting strips. In this way, an internal 11. K.L. Wong and C.H. Chang, An EMC foam-base chip antenna for
multiband monopole antenna with one shorting wall (4 mm in WLAN operation, Microwave Opt Technol Lett 47 (2005), 80 – 82.
width) and two separate feeds [see inset in Fig. 8(a)] is obtained. 12. S.W. Su and K.L. Wong, Wideband antenna integrated in a system in
The results of the simulated reflection coefficient (S11 for the 700 package for WLAN/WiMAX operation in a mobile device, Microwave
MHz antenna, S22 for the WLAN/WiMAX antenna) and isolation Opt Technol Lett 48 (2006), 2048 –2053.
(S21) between the two antennas are shown in Figure 8(a). Com- 13. S.W. Su and J.H. Chou, Internal 3G and WLAN/WiMAX antennas
integrated in palm-sized mobile devices, Microwave Opt Technol Lett
pared with Figure 3(b), the isolation level here has been deterio-
50 (2008), 29 –31.
rated by about 5 dB (from 20 to 15 dB) and 10 dB (from 30
14. K.L. Wong, S.W. Su, C.L. Tang, and S.H. Yeh, Internal shorted patch
to 20 dB), respectively, over the 700-MHz band and the WLAN/ for a UMTS folder-type mobile phone, IEEE Trans Antennas Propag
WiMAX band. Nevertheless, the isolation is still less than about 53 (2005), 3391–3394.
15 dB, which is most of the time adopted for many mobile-phone 15. C.M. Su, K.L. Wong, C.L. Tang, and S.H. Yeh, EMC internal patch
antenna applications in industry. Moreover, it is worth studying the antenna for UMTS operation in a mobile device, IEEE Trans Antennas
effects of inserting a RF-shielding cylinder for a CCD used in an Propag 53 (2005), 3836 –3839.
embedded digital camera between the two antennas [see inset in
Fig. 8(b)]. Figure 8(b) shows the simulated S parameters (S11, S22, © 2008 Wiley Periodicals, Inc.
S21) of the two proposed antennas with a CCD shielding cylinder
(diameter 5 mm, 6 mm in height). It is easily seen that both the
antenna operating bands and isolation are almost the same as
compared with those in Figure 3(b). This phenomenon suggests
OPTICAL FIBER SENSOR FOR
that the fringing EM fields around the antenna shorting strip/ LOCALIZING HEATING POSITIONS IN
portion can be lessened to some degree, as a relaxed alternative to MULTIPLE POINTS USING
a large shielding wall [14, 15]. MULTICHANNEL GRATINGS WITH
PHASE SAMPLING AND WAVELENGTH
4. CONCLUSION DIVISION MULTIPLEXING TECHNIQUES
Two integrated, internal antennas, obtained from cutting a metal Li Xia and P. Shum
plate, for 700 MHz and WLAN/WiMAX operation for palm-sized Network Technology Research Centre, Nanyang Technological
mobile devices have been presented. A design prototype mounted University, Singapore 639798; Corresponding author:
near one side of the system circuit board with the antenna shorting xiali@ntu.edu.sg
strips facing each other has been constructed and tested. Good port
isolation between the two antennas over the operating bands has Received 2 March 2008
been achieved. Furthermore, the two proposed antennas can be
integrated into a single antenna element simply by connecting both ABSTRACT: An optical fiber sensor system with multichannel fiber
shorting strips, leading to a multiband antenna with two individual Bragg gratings (FBGs) is proposed. The gratings are designed and fab-
feeds for multinetwork operation. ricated by phase sampling technique within strongly chirped phase
masks. The sensing application can be realized at multiple points
through wavelength division multiplexing (WDM) technique. It means
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