4. CONCLUSIONS
                                                                        CoFe and NiFe spiral FM inductors h...
other and a shorting strip that connects both radiating arms. The
                                                        ...
Figure 5 Measured peak antenna gain and measured radiation efficiency
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A One-Piece Flat-Plate Dipole Antenna for Dual-Band WLAN Operation

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A simple, one-piece, flat-plate dipole antenna suitable for dual-band WLAN applications is presented. The antenna is structured to be of an L shape to fit in corners of possible wireless electronics devices. The two radiating arms of the dipole antenna are further short-circuited through a narrow shorting strip at the corners, making it possible for the antenna to be manufactured by stamping a single, flat metal plate only one time. That is, the proposed antenna in the mass-production phase can be at lower cost. In addition, by cutting an L-shaped slit at proper location in each radiating arm, a dual-band operation can easily be obtained. The design prototype of the antenna in the 2.4/5.2 GHz bands is discussed in detail in the article.

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A One-Piece Flat-Plate Dipole Antenna for Dual-Band WLAN Operation

  1. 1. 4. CONCLUSIONS CoFe and NiFe spiral FM inductors have been fabricated and their characteristics have been compared. Both inductors showed en- hancements in inductance over the conventional inductors, while the improvement was more significant for the NiFe inductors reaching as high as 28%. The Q-factor tended to be lower for the FM inductors, but the degradation was partially recovered by slit-patterning the FM layer. The result in this work marks the first successful application of CoFe and NiFe FM layers to spiral inductors for improved inductance. ACKNOWLEDGMENTS This work was supported by MIC, Korea, under ITFSIP supervised by IITA and Korea University Grant. REFERENCES 1. M. Danesh and J.R. Long, Differentially driven symmetric microstrip inductors, IEEE Trans Microwave Theory Tech 50 (2002), 332. 2. M. Yamaguchi, M. Baba, and K.I. Arai, Sandwich-type ferromagnetic RF integrated inductor, IEEE Trans Microwave Theory Tech 49 (2001), 2331-2335. 3. M. Yamaguchi, M. Baba, K. Suezawa, T. Moizumi, K.I. Arai, Y. Shimada, A. Haga, S. Tanabe, and K. Ito, Magnetic RF integrated thin-film inductors, IEEE MTT-S Dig (2000), 205-208. 4. M. Yamaguchi, K. Suezawa, M. Baba, K.I. Arai, Y. Shimada, S. Tanabe, and K. Itoh, Application of bi-directional thin-film micro wire array to RF integrated spiral inductors, IEEE Trans Magn 36 (2000), 3514-3517. 5. B. Viala, A.S. Royet, R. Cuchet, M. Aid, P. Gaud, O. Valls, M. Ledieu, and O. Acher, RF planar ferromagnetic inductors on silicon, IEEE Trans Magn 40 (2004), 1999-2001. 6. A.M. Crawford, D. Gardner, and S.X. Wang, High-frequency micro- inductors with amorphous magnetic ground planes, IEEE Trans Magn 38 (2002), 3168-3170. 7. T. Saito, K. Tsutsui, S. Yahagi, Y. Matsukura, H. Endoh, T. Eshita, and K. Hikosaka, Quasi-microwave-range inductors covered with co- based magnetic thin films, IEEE Trans Magn 35 (1999), 3187-3189. 8. Y. Zhuang, M. Vroubel, B. Rejaei, and J.N. Burghartz, Ferromagnetic RF inductors and transformers for standard CMOS/BiCMOS, IEDM Figure 4 Inductance and Q-factor comparison of slit-patterned FM in- Tech Dig (2002), 475-478. ductors with 6-turns (N 6): (a) CoFe FM inductor (b) NiFe FM inductor 9. Y. Zhuang, B. Rejaei, E. Boellaard, M. Vroubel, and J.N. Burghartz, Integrated solenoid inductors with patterned, sputter-deposited Cr/ Fe10Co90/Cr ferromagnetic cores, IEEE Electron Device Lett 24 (2003), 224-226. feature for the slit-patterned devices over the blanket ones is the 10. J.N. Burghartz and B. Rejaei, On the design of RF spiral inductors on significantly improved Q-factor, which arises from the increase in silicon, IEEE Trans Electron Devices 50 (2003), 718-729. the demagnetizing field with the slit patterns [2]. For the 6-turn device as depicted in Figure 4(a), the reduction in Q-factor from © 2008 Wiley Periodicals, Inc. the conventional inductor is improved from 34.4% to 8.5% at 1 GHz for the CoFe inductors. The Q-factor of the slit-patterned NiFe inductors at 1 GHz is actually larger than that of the con- ventional inductors by 1.6%, compared with the 28.4% reduction A ONE-PIECE FLAT-PLATE DIPOLE for the blanket one [Fig. 4(b)]. The peak Q-factor is still lower for ANTENNA FOR DUAL-BAND WLAN both CoFe and NiFe inductors compared to the conventional OPERATION inductors. Saou-Wen Su,1 Jui-Hung Chou,1 and Yung-Tao Liu2 1 The primary effect of the slit patterns on the inductance is the Technology Research Development Center, Lite-On Technology shifted roll-off point toward the higher frequency, leading to a Corporation, Taipei 11492, Taiwan; Corresponding author: stephen.su@liteon.com and susw@ms96.url.com.tw wider inductance bandwidth. While the NiFe inductors showed a 2 Department of Physics, R.O.C. Military Academy, Feng-Shan slight inductance decrease for the slit patterns compared to the 83059, Taiwan blanket case, which is consistent with the reports on CoNbZr inductors, the CoFe inductors did not show such degradation as Received 7 August 2007 indicated by Figure 4(a). Finally, it is noteworthy that the induc- tance of the slit-patterned inductors investigated in this work did ABSTRACT: A simple, one-piece, flat-plate dipole antenna suitable for not show noticeable dependence on the relative orientation of the dual-band WLAN applications is presented. The antenna is structured to slit against the magnetic axis (easy or hard). be of an L-shape to fit in corners of possible wireless electronics de- 678 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 3, March 2008 DOI 10.1002/mop
  2. 2. other and a shorting strip that connects both radiating arms. The designed dipole structure can be installed at around corners inside wireless electronics devices, for example wireless printers and audio adapters, for practical applications. The antenna can be fed by short 50- mini-coaxial line with an I-PEX connector. The central conductor is connected to the point A and its outer ground- ing sheath is soldered to the point B. The point A and B can be designated vice versa due to the dipole antenna symmetrical in shape. Notice that, in order to achieve a near optimal impedance matching over the antenna operating bands, two small feeding strips located along the smaller edges of the radiating arms are utilized. The gap (distance 3 mm in this study) between the feeding strip and the shorting strip plays an important role in the imped- ance matching, similar to the characteristic of matching a planar inverted-F antenna (PIFA) as a general rule of thumb. Figure 1 Proposed flat-plate dipole antenna for dual-band WLAN op- In general, both radiating arms are rectangular in shape with the eration. [Color figure can be viewed in the online issue, which is available dimensions 20.5 mm (L) 8 mm (W). When there are no L- at www.interscience.wiley.com] shaped slits, the two rectangular dipole arms form a simple dipole antenna (the larger dipole antenna) for operating in the 2.4 GHz band. The center operating frequency of the antenna lower reso- vices. The two radiating arms of the dipole antenna are further short- nant mode for the 2.4 GHz band operation can be determined circuited through a narrow shorting strip at the corners, making it pos- approximately by the length (L) and the width (W). That is, the sible for the antenna to be manufactured by stamping a single, flat metal plate only one time. That is, the proposed antenna in the mass- sum of the L and W corresponds to a free-space quarter-wave- production phase can be at lower cost. In addition, by cutting an L- length at about 2442 MHz. Further, with the presence of a proper shaped slit at proper location in each radiating arm, a dual-band oper- L-shaped slit cut in each radiating arm, two additional, shorter ation can easily be obtained. The design prototype of the antenna in the radiating arms, which form a smaller dipole antenna, are obtained 2.4/5.2 GHz bands is discussed in detail in the article. © 2008 Wiley for generating a higher (new) resonant mode for the 5.2 GHz band Periodicals, Inc. Microwave Opt Technol Lett 50: 678 – 680, 2008; operation. Thus, the proposed, flat-plate dipole antenna is capable Published online in Wiley InterScience (www.interscience.wiley.com). of performing dual-band WLAN operation in the 2.4 and 5.2 GHz DOI 10.1002/mop.23179 bands. Key words: antennas; dipole antennas; metal-plate antennas; dual-band 3. RESULTS AND DISCUSSION antennas; WLAN antennas Figure 2 shows the measured and simulated return loss of the design prototype. Good agreement between the experimental data 1. INTRODUCTION and simulation result, based on the finite element method (FEM), Dipole antennas are simple in structure and have good radiation is seen. For frequencies over the 2.4/5.2 GHz WLAN bands, the characteristics. Most of them are in the form of printed dipole measured impedance matching is all better than 10 dB return loss. structures [1-6] with two radiating arms spaced apart. Very scant The lower resonant mode shows a wide bandwidth of 289 MHz attention has been paid to dipole antennas in the form of flat, (2280 –2569 MHz), which easily covers the 2.4 GHz band for metal-plate structure. The reason behind that owes probably to the WLAN operation. The higher resonant mode has a bandwidth of structure of two separate radiating arms such that dipoles cannot 472 MHz (5150 –5622 MHz), which meets the bandwidth require- easily be fabricated. Further, for practical applications, coaxial- ment of the 5.2 GHz WLAN band. line-fed dipole antennas of a small form factor [2] are more costly by etching on a printed circuit board (PCB) than by stamping a piece of metal plate. In this article, we demonstrate a one-piece, metal-plate dipole antenna of a small form factor for dual-band WLAN operation in the 2.4 GHz (2400 –2484 MHz) and 5.2 GHz (5150 –5350 MHz) bands. The antenna has a flat structure, stamped from a single metal plate only one time, and comprises two radiating arms perpendicular to each other and a narrow shorting strip that short-circuits both radiating arms. Moreover, with proper L-shaped slits cut in both radiating arms, a new, higher resonant mode in the 5.2 GHz band can be obtained, in addition to the initial, lower resonant mode in the 2.4 GHz band with no slits, for the antenna. In this case, a flat-plate dipole antenna with two separate operating bands for 2.4/5.2 GHz WLAN operation can be achieved. The proposed antenna is suitable to be assembled in corners of wireless electronics devices for dual-band WLAN ap- plications. 2. ANTENNA DESIGN Figure 1 shows the configuration of the proposed antenna. The Figure 2 Measured and simulated return loss for the design prototype. antenna is constructed from stamping a piece of flat metal plate at [Color figure can be viewed in the online issue, which is available at low cost and consists of two radiating arms perpendicular to each www.interscience.wiley.com] DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 3, March 2008 679
  3. 3. Figure 5 Measured peak antenna gain and measured radiation efficiency for the dipole antenna studied in Figure 2. [Color figure can be viewed in Figure 3 Measured radiation patterns at 2442 MHz. [Color figure can be the online issue, which is available at www.interscience.wiley.com] viewed in the online issue, which is available at www.interscience.wiley.com] Figures 3 and 4 plot the measured radiation patterns at 2442 and a shorting strip, can offer a promising antenna solution for and 5250 MHz, respectively. Similar to the conventional, wire- keeping cost down. Moreover, in addition to the lower resonant dipole radiation characteristics, good omnidirectional-radiation mode controlled by the dimensions of the rectangular radiating pattern in the x-z plane is first seen for the 2442 MHz operation. arm, the higher resonant mode can easily be obtained by cutting The omnidirectional radiation exists in the cut (see segmented line L-shaped slits in both dipole arms at suitable locations. Good in inset) that is a symmetrical plane, in geometry, for the proposed radiation characteristics of the dipole antenna have been also dipole antenna of an L shape. For the case at 5250 MHz, however, observed. less omnidirectional, x-z-plane pattern can be achieved. This is largely because the surface currents are in the opposite direction, REFERENCES over the slit, in the smaller dipole arms and in the top portions of 1. Y.H. Suh and K. Chang, Low cost microstrip-fed dual frequency printed the larger radiating arms, respectively. Thus, the radiated fields in dipole antenna for wireless communications, Electron Lett 36 (2000), the direction normal to the proposed antenna can be destructive to 1177-1179. some degree. Figure 5 shows the measured peak antenna gain and 2. C.M. Su, H.T. Chen, and K.L. Wong. Printed dual-band dipole antenna the measured radiation efficiency against frequency. The far-field with U-slotted arms for 2.4/5.2 GHz WLAN operation, Electron Lett 38 antenna measurement was conducted at the 3 m 3m 7m (2002), 1308-1309. anechoic chamber at Lite-On Technology Corp., Taipei. The an- 3. Y.F. Liu, Q. Xue, and C.H. Chan, A novel dual-band printed-dipole antenna using CRC structure, Microwave Opt Technol Lett 41 (2004), tenna gain in the 2.4 GHz band has a gain level of about 3.3 dBi, 105-106. with the radiation efficiency about 84%. In the 5.2 GHz band, the 4. Y.T. Liu, T.C. Tseng, and K.L. Wong, High-gain printed dipole an- antenna gain varies within a small range of about 4.1– 4.9 dBi and tenna, Microwave Opt Technol Lett 46 (2005), 214-218. the radiation efficiency exceeds about 80%. 5. K. Chang, H. Kim, and Y.J. Yoon, A triple-band printed dipole antenna using parasitic elements, Microwave Opt Technol Lett 47 (2005), 221-223. 4. CONCLUSION 6. J.M. Floc’h and H. Rmili, Design of multiband printed dipole antennas A novel, one-piece, flat, metal-plate dipole antenna capable of using parasitic elements, Microwave Opt Technol Lett 48 (2006), 1639- providing a dual-band operation in the 2.4/5.2 GHz WLAN bands 1645. has been constructed and tested. The proposed design with a © 2008 Wiley Periodicals, Inc. single, metal-plate structure, composed of L-shaped radiating arms PARALLEL-COUPLED BANDPASS FILTER WITH IMPROVED REJECTION SLOPE USING -OFFSET LENGTH Johnson Soh,1 Siou Teck Chew,2 and Ban-Leong Ooi3 1 National University of Singapore, Singapore; Corresponding author: g0600143@nus.edu.sg 2 iCREDO Technologies Pte Ltd, Singapore 3 Department of electrical and computer engineering, National University of Singapore, Singapore Received 11 August 2007 ABSTRACT: In this article, a novel method to improve the rejection of edge coupled filters by perturbing the coupled line sections by a length, , is introduced. This gives controls over the null position between the funda- Figure 4 Measured radiation patterns at 5250 MHz. [Color figure can be mental and 1st harmonic of the filter which results in a steeper rejection viewed in the online issue, which is available at www.interscience.wiley.com] slope by shifting this null closer to the centre frequency. A 4th order 5 GHz 680 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 3, March 2008 DOI 10.1002/mop

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