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internet device (MID) or ultramobile PC (UMPC) [4]. The two
INTEGRATION OF INTERNAL 700 MHz                               ...
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 is...
is seen to be in the direction of the system ground plane ( x
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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, Sh...
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Integration of Internal 700 MHz and WLAN/WiMAX Antennas for Palm-Sized Mobile Devices

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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.

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Integration of Internal 700 MHz and WLAN/WiMAX Antennas for Palm-Sized Mobile Devices

  1. 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. 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. 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. 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 REFERENCES that the different point can be monitored by different gratings, which 1. Federal Communications Commission, 2007. 700 MHz second report occupies different wavelength region, according to the central pitch and and order. Available at: http://fjallfoss.fcc.gov/edocs_public/attach- chirp coefficient of phase masks. The heating position with high resolu- match/FCC-07-132A1.pdf. tion can be analyzed through three corresponding channel shifts in the 2. Federal Communications Commission. Auction 73: 700 MHz band. multichannel profile. In our experiment, the two multichannel gratings Available at: http://wireless.fcc.gov/auctions/default.htm?job auction_ with channel spacing of 0.8 and 1.6 nm, respectively, are fabricated and factsheet&id 73. used for sensing in two points. At last, the 400 m accuracy of localiz- 3. WiMAX Forum, 2005. Deployment considerations for fixed wireless ing the heating position is achieved. © 2008 Wiley Periodicals, Inc. access in 2.5 GHz and 3.5 GHz license bands. Available at: http:// Microwave Opt Technol Lett 50: 2951–2954, 2008; Published online in www.wimaxforum.org/news/downloads/DeploymentConsiderations_ Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop. White_PaperRev_1_4.pdf. 23832 4. Intel. Mobile internet device and ultra mobile PC. Available at: http:// www.intel. com/products/mid/index.htm. Key words: optical fiber sensor; fiber Bragg grating (FBG); multichan- 5. K.L. Wong, J.H. Chou, C.L. Tang, and S.H. Yeh, Integrated internal nel; phase sampling GSM/DCS and WLAN antennas with optimized isolation for a PDA phone, Microwave Opt Technol Lett 46 (2005), 323–326. 1. INTRODUCTION 6. K.L. Wong, S.W. Su, T.W. Chiou, and Y.C. Lin, Dual-band plastic chip antenna for GSM/DCS mobile phones, Microwave Opt Technol Nowadays, optical fiber sensors are more attractive in various Lett 33 (2002), 330 –332. areas because of their immunity to electromagnetic interference, 7. H.C. Tung, C.Y. Fang, and K.L. Wong, An inverted-L monopole high sensitivity, compactness, and simplicity of fabrication [1]. antenna loaded with a meandered wire for GSM/DCS dual-band mo- Among these, optical fiber distributed monitoring [2] is particu- bile phones, Microwave Opt Technol Lett 33 (2002), 212–214. larly useful in several situations, such as when there is no prior DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 11, November 2008 2951

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